***Useful Information For The Working Sparky***

[amberleaf]

FOR DESIGN, CONSTRUCTION, INSPECTION & TESTING :

I being the person responsible for the Design, Construction, Inspection & Testing of the electrical
installation (as indicated by my signature below), particulars of which are described above, having
exercised reasonable skill and care when carrying out the Design, Construction, Inspection & Testing,
hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge
and belief in accordance with BS-7671:2008 , amended to .............(date) except for the departures, if any, detailed as follows ,

(vi) A Minor Works Certificate will indicate the responsibility for design, construction, inspection and testing of
the work described on the certificate.
(vii) A Periodic Inspection Report will indicate the responsibility for the inspection and testing of an installation
within the extent and limitations specified on the report.
(viii) A Schedule of Inspections and a Schedule of Test Results as required by part 6 should be issued with the
associated Electrical Installation Certificate or Periodic Inspection Report.
(ix) When making out and signing a form on behalf of a company or other business entity, individuals should
state for whom they are acting.
(x) Additional forms may be required as clarification, if needed by ordinary persons, or in expansion, for large
or more complex installations.
(xi) The IEE Guidance Note 3 provides further information on inspection and testing on completion and for periodic inspections ,

ELECTRICAL INSTALLATION CERTIFICATES NOTES FOR FORMS 1 AND 2 :
1. The Electrical Installation Certificate is to be used only for the initial certification of a new installation or
for an addition or alteration to an existing installation where new circuits have been introduced.
It is not to be used for a Periodic Inspection, for which a Periodic Inspection Report form should be used.
For an addition or alteration which does not extend to the introduction of new circuits, a Minor Electrical
Installation Works Certificate may be used.
The "original" Certificate is to be given to the person ordering the work (Regulation 632.1 . A duplicate
should be retained by the contractor.
2. This Certificate is only valid if accompanied by the Schedule of Inspections and the Schedule(s) of Test
Results.
3. The signatures appended are those of the persons authorized by the companies executing the work of
design, construction, inspection and testing respectively. A signatory authorized to certify more than
one category of work should sign in each of the appropriate places.
4. The time interval recommended before the first periodic inspection must be inserted (see IEE
Note 3 for guidance).
5. The page numbers for each of the Schedules of Test Results should be indicated, together with the total
number of sheets involved.
6. The maximum prospective fault current recorded should be the greater of either the short-circuit current or
the earth fault current.
7. The proposed date for the next inspection should take into consideration the frequency and quality of
maintenance that the installation can reasonably be expected to receive during its intended life, and the
period should be agreed between the designer, installer and other relevant parties

SCHEDULES (note 2)
The attached Schedules are part of this document and this Certificate is valid only when they are attached to it.
............ Schedules of Inspections and ............ Schedules of Test Results are attached
(Enter quantities of schedules attached)

GUIDANCE FOR RECIPIENTS
This safety Certificate has been issued to confirm that the electrical installation work to which it relates has been designed, constructed, inspected and tested in accordance with
British Standard 7671 (the IEE Wiring Regulations).
You should have received an "original" Certificate and the contractor should have retained a duplicate. If you were the person ordering the work, but not the owner of the
installation, you should pass this Certificate, or a full copy of it including the schedules, immediately to the owner.
The Certificate should be retained in a safe place and be shown to any person inspecting or undertaking further work on the electrical installation in the future. If you later vacate
the property, this Certificate will demonstrate to the new owner that the electrical installation complied with the requirements of British Standard 7671 at the time the Certificate
was issued. The Construction (Design and Management) Regulations require that for a project covered by those Regulations, a copy of this Certificate, together with schedules is
included in the project health and safety documentation.
For safety reasons, the electrical installation will need to be inspected at appropriate intervals by a competent person. The maximum time interval recommended before the next
inspection is stated on Page 1 under "Next Inspection".
This Certificate is intended to be issued only for a new electrical installation or for new work associated with an addition or alteration or to an existing installation. It should not
have been issued for the inspection of an existing electrical installation. A "Periodic Inspection Report" should be issued for such an inspection ,
The Certificate is only valid if a Schedule of Inspections and Schedule of Test Results are appended ,

Excess earth leakage
The RCDs operating principle is to measure the current imbalance between that flowing into and out of a circuit down live and neutral wires. In an ideal world the current difference would be zero, however in the real world there are a various different types of equipment that will legitimately have a small amount of leakage to earth, even operating normally. If the RCD is protecting too many such devices then it is possible that the cumulative result of all these small leakages will be enough to either
• trip the RCD
• or by passing most of the RCD's trip threshold current, make the RCD excessively sensitive to any additional leakage currents
Appliances that typically exhibit high leakage currents
Dampness : Any device that handles water and electricity will be vulnerable to dampness getting into electrical connections or wiring harnesses. This can result in short term high levels of leakage that mysteriously vanish later (as the affected item dries out). Even condensation forming in equipment can cause this problem.

Split water heater elements. These cause gross earth leakage, and conduct it directly through the water being heated. Contrary to what we were taught about electricity and water in primary school, this does not cause electrocution in practice. Split elements can however cause overcurrent leading to overheating of electrical accessories.

DC Resistance tests :
First ensure that power is switched off at the main switch. Ensure all appliances are disconnected from the circuit. These tests require that you disconnect the circuit under test from the consumer unit. In the case of a Ring circuit remember to disconnect both legs of the ring. All tests are initially performed on the disconnected ends of the circuit.
There are a number of basic tests that you can do that will identify a great many of the fixed wiring faults that can cause nuisance tripping.
Test :
Live / Neutral Resistance

Purpose :
The first test is a simple resistance test between live and neutral. This test should be done using the highest resistance range on your multimeter. Normally with all the appliances disconnected you would expect to see an open circuit between live and neutral. If this is not the case then you either have something still connected, or you have a serious insulation resistance problem.

Live Earth Resistance :
This test should also indicate an open circuit with the multimeter on its highest resistance measuring range. Any non infinite reading here could be a direct indication of your problem. If you get a non infinite resistance reading, you may be able to track down the location of the fault by breaking the circuit up at strategic points ( typically by disconnecting part of it at an accessory position ).
Again this test ought to indicate infinite resistance. However it is possible that a very low resistance measurement could exist and yet the circuit still work some of the time (especially on systems with TN-C-S Earthing ). Unlike a low resistance reading on a Live to Earth test, this fault would not immediately trip a MCB or blow a fuse .
Neutral Earth Resistance :
Tracing the location of the short or bridge can again be done using the segmenting procedure described above, and also by careful low resistance measurements made in conjunction with expected cable resistances (or see the table in the IEE Wiring Regulations On Site Guide ).
A typical cause of this type of fault, is where a concealed cable has been damaged by a fastening being driven through it. (so if any shelves or pictures have been hung recently, there is a good place to start looking).

 

[amberleaf]

What is a TT Earth and why would I want one ?
If you refer to the Earthing Types article you will see there are a number of ways that an earth can be provided for an electrical installation Of the available types TN-S and TN-C-S, where your electricity supplier also provide an earth, are by far the most common. The next most common category is the TT type. You will encounter this situation where the electricity supplier does not provide any connection to allow the installation to be earthed, or you are working on an electrical installation in an outbuilding where it was not appropriate to export the main earth . In either of these cases you are responsible for providing your own earth connection.
Since a TT earthing system will safeguard both lives and equipment it is important that a correctly designed system is installed. It should have:
* Low enough electrical resistance to earth to ensure correct operation of the circuit earth fault protection device ( typically a RCD ).
* Good repeatability (i.e. it should be able to carry fault currents repeatedly, and its performance should remain in spec all year round, irrespective of varying soil conditions)
* High resistance to corrosion ,
* Long life expectancy ,
Types of earth electrode :
The usual way to provide an earth is to place an electrode into the soil. There are a number of ways of doing this, and how well each of them will work will depend to a large extent on the local soil conditions.
Earth Rods or Spikes :
Earth rods are commonly used since they are easy to retrofit to properties and also work well for a relatively small overall rod area. A typical earth rod is 1.2m long and something like 9 to 14mm in diameter, and usually made from copper clad steel, solid copper, or sometimes stainless steel. This is driven into the ground and an electrical connection made to the top of it via an earth clamp. If the resistance achieved with one rod is too high, then most rods have a threaded section that will allow an additional one to be connected to it, and then that too driven into the ground. (Note that the overall length of the electrode has far more effect on the resistance than the diameter).
The connection to the earth rod should be protected with a suitable enclosure, and this must feature a warning label stating that "this is a safety electrical connection and should not be removed."
Driving an earth rod
The usual solution to this is to hit it with a hammer, and keep doing so until it is nearly all gone. However a modern and much simpler equivalent is to use a SDS drill set to hammer only (i.e. rotation stop) mode, fitted with a square drive adaptor and a socket. The socket will keep the drill centered on the spike and should allow you to "power drive" it into the soil.
For many rod sizes you may also obtain a "driving head". This is a cover that will protect the top end of the rod from damage while driving, which will be important if you need to attach and drive further rods to the first one.
You should choose a section of ground that is away from other service pipes and drains, and preferably is comprised of ordinary soil rather than builders rubble. This will not only make driving the spike easier, but will get a lower resistance electrode as a result.
If the spike hits something immovable and will not drive any further you may be able to pull it out and try elsewhere, or if you managed to drive mostly home before it stopping then it may be worth testing as is and cutting off the excess if the result is good enough. If one rod position on its own is not good enough then additional rods can be driven in other locations and "paralleled up" to lower the overall resistance.
It is wise to try an keep a few meters away from other rods so as not to overlap their resistance area (how far, will depend on how good a conductor the local soil is. The poorer it is the closer they can be together).

Earth Plates :
These are typically either solid copper plates, or lattice like plates made from copper rods. These need to be buried in suitable ground. They can not be "driven" later, and require excavation of soil to fit.
Alternative earth types :
Alternative systems are sometimes used such as earth tapes or wires that are run through long channels dug in the ground. Again difficult to retrofit, and not suitable for soils that require deep penetration to reach permanently damp and frost free conditions. There is also an earthing system constructed using the foundation slab of some building types called an Ufer Earthing
Quality of earth :
The quality of the earth obtained will depend to a large extent on the soil moisture content. Soils that stay damp all year round (like heavy clay) will often perform well in this context. You may need more than one rods length to reach the permanently damp soil.
Different soil types will affect the performance. Marshy ground will perform best, with loam, clay, peat and often chalk also working well when damp. Dry sand and rocky ground however can be much harder to get good results with.
Pay attention to temperature range as well. Frozen ground can be ten times less effective than warmer soil.
Soils with high mineral salt content in their moisture will usually perform noticeably better than "ordinary" damp soil.
Testing the electrode resistance :

The aim of the exercise is to achieve a reasonably low resistance path to earth. Usually with this type of earth it is unrealistic to expect to achieve a resistance as low as that you would get from a supplier provided earth (i.e. under 1 ohm), however it is usually easy to achieve a resistance well under 100 ohms, which when combined with a RCD will offer adequate protection.
When testing the resistance of an earth electrode it is important that any parallel connections to earth (such as main equipotential bonds to water or gas mains) are disconnected when the reading is taken. Note that this in itself raises a danger since some of the buildings equipotential zone will be disconnected, and any other occupants of the premises should be warned.
Without specialist test gear :
Anyone with a bit of electrical common sense, knowledge of Ohm's law, and a decent multimeter can measure earth electrode resistance quite easily. You need to isolate the electrode in question and then find a way of getting some current to flow into it. A safe way to do this is to use a double-wound mains transformer with a secondary voltage of around 24V (exact value not critical).
Exactly how you wire this up will depend on the circumstances. If you have a TN system installation where you are adding an earth electrode for an outbuilding etc, then you can make use of your existing supplier provided earthing point as a return path: Connect one end of the secondary via a suitable length of wire to the main earth terminal in the house and connect the other end to your earth electrode via an ammeter.
Energise the primary of the transformer, and the secondary current which flows will immediately give you a rough idea of the total resistance in the circuit, most of which will be attributable to your electrode. For a more accurate result, drive a second temporary earth electrode (a 2ft offcut of 15mm water pipe will do) into the ground at a distance of 10m or more from the one you're measuring. Then use the meter on volts to measure the voltage drop between the two electrodes. Dividing this figure by the electrode current measured earlier gives you the earth resistance. (Reactance in the circuit will be negligible.) Move the temporary reference electrode to a second position and repeat. Average the two values obtained, but if they are significantly different, try further positions for the reference electrode.
If your whole installation is TT system to start with, and you need to measure the impedance of the main or a secondary electrode, then you will need to use another temporary earth connection as a return path. bash a bit of copper water pipe (or similar) into the ground as far away from the electrode under test as you can manage, and use that to complete the circuit. With this technique you must use the separate sensing electrode (a 2nd temporary rod) to establish a voltage reference. Put this one roughly half-way between the other two, and take measurements with it in two or three different places to check that the resistance areas aren't overlapping too much.

 

[amberleaf]

This could mean the difference between life and death. Apprentice :
We need to remember the following :-

1. When properly connected an electric current flows through the live wire on its way to the appliance and returns to ground via the neutral wire.
2. If for some reason the current “leaks” ( through dampness, frayed wiring, faulty connections etc ) the current will take the most direct path to earth – often through a person’s body. In this situation if the power is not disconnected instantly then there is a strong possibility that the person will die.
3. The path taken by the current also contributes to the severity of the electric shock. An electric shock which flows from the hand through the arms and to the chest will affect the breathing and heartbeat.
4. The greatest contributing factor to the severity of an electric shock is the exposure time to the current. An RCD cuts off the power in less than the time of a single heartbeat.
An RCD can be tested in two ways :-
1. A push button test – this requires no test instrument.
2. By the use of an RCD Tester – an RCD Tester is designed to check the trip current and trip time. Most RCD Testers can measure from 1 millisecond to 2000 milliseconds .
Many RCD Testers will be capable of conducting both an AC and DC test, Note :
The Standard BS-7671requires that RCDs are tested for trip times at specified intervals i.e. not just a push button test. An RCD Tester is required for this tripping time test.
Earth Testing :
Legally it is a requirement – but is it really necessary ?
Potentially the most dangerous appliances are Class I appliances (earthed appliances) e.g. floor polishers and the like, but also in this category are extension leads.

Class I appliances are designed to have an earth – this means that in the example of the floor polisher the body of the polisher is connected to earth - literally to the ground via an earth conductor which goes right back to the building switchboard and then into the ground the building is sitting on.

If this conductor is damaged anywhere then the consequences can be fatal – I will explain this point in greater detail shortly. It is obvious therefore that the conductor needs to be tested.

Insulation Resistance & Leakage Testing
Insulation resistance tests MUST NOT be carried out using ohmmeters or multimeters because these meters only produce a small battery voltage in the region of 1.5 to 9 volts. This small voltage is insufficient to pressure test the insulation to expose any weakness in it and therefore is totally inappropriate for insulation resistance tests.

Insulation resistance testers and PATs on the other hand are specifically designed to produce 500 volts (or even greater voltage values for some applications) which places the insulation under stress. This test will indicate any weakness that may break down under normal use on the 230 volt supply.

It is a requirement that the resistance measured by the insulation tester in this way should be not less than 1 megohm (1,000,000 ohms) for an electrical appliance to pass this test.

A practical example showing how a multimeter or ohmmeter is inappropriate to test the insulation resistance of an electrical appliance is detailed by the following example:

A 230-volt floor polisher has a partial insulation breakdown between the motor windings and the earthed metal case. The polisher when in use and at its normal operating temperature, causes the sub-circuit protective fuse to blow as a result of the insulation breaking down to the earthed metal frame.
The polisher, when tested with an ohmmeter or multimeter, does not indicate the presence of a fault, as the meter voltages are so low that they do not stress the insulation and therefore do not reproduce the breakdown that occurs when the appliance is in use.
However, testing the same polisher with an insulation resistance tester producing an output of 500 volts causes the insulation to break down under test, thereby indicating a low insulation resistance value and the presence of a fault path.
NOTE The importance of a sound low resistance earth continuity conductor is paramount to the safety of any electrical appliance that requires an Earth. A test as described above would not achieve anything if the integrity of the Earth were not first proven to be in good condition. Should the appliance have an open circuit Earth continuity conductor, it would produce a high resistance test result, but in fact when the appliance was plugged in it would enliven the case and expose a potential shock hazard.

APRENTICE : ELECTRICAL RING MAIN OR RADIAL CIRCUIT :
A ring main is exactly what it says on the tin. It is a ring of wires, circling your home, carrying the mains electricity to sockets on the way. It gets the power from the Consumer Unit and delivers it to the sockets. As both ends of the ring are connected to the same terminals at the consumer unit, the current runs in both directions imposing less of a load on the cables. Electricity loses power over long lengths of cable and trying to put too much power through a cable which is not designed for it, is dangerous, so a ring main delivers power from both ends to keep the load as light as possible.
A radial circuit is a mains power circuit found in some homes to feed sockets and lighting points. It is simply a length of appropriately rated cable feeding one power point then going on to the next. The circuit terminates with the last point on it. It does not return to the Consumer Unit or fuse box as does the more popular circuit, the Ring Mains. To see the wiring at the back of the socket please go to the ring main project.
There is no limit to the number of sockets used on a radial circuit providing the circuit is contained within an area not exceeding 50 square m, and, just like a ring main, spurs, or extra sockets, can be added. The number of spurs must not exceed the number of existing sockets. Regs , p-363
A separate ring main is usually installed on every floor of the house to make sure things are kept safe and it is only when, for example, a spur (additional socket) is added on an upstairs ring main, to feed a socket or light on a downstairs circuit, that things can get tricky. Please read Part P Building Regulations / Regs , 314.4
A ring main uses 2.5mm cable comprising of a live, neutral and earth. This is called two core & earth cable. The 2.5mm is the measurement of the cross sectional area of the cables.
The floor area a ring main serves is also governed. This is because the regulation people have some idea of how much power and lighting we can expect to use in such an area. The maximum area for a ring main is 100 square meters. An average house has a footprint of about 64-70 square meters so this allows for the continuation of the ring into a porch or garage etc. The ring main must be protected by a 32amp MCB.
The cable itself can be up to 60 meters long if it is protected by a cartridge fuse and 50 meters long if protected by an MCB.
There is no limit to the number of sockets you can have on a ring main but there is a limit to the number of spurs you can have from those sockets or from the wiring between them. on adding an extra socket. You can also extend the ring main if you need to.
Units or appliances which use a lot of power, like cookers and showers must be installed on their own circuits so please check the appliances you are considering using on your ring main. It is also a regulation that any socket which is capable of being used to supply power outside of the house is protected by an RCD.,

Apprentice : An MCB is a form of fuse (protective device) which overcomes the traditional problem associated with fuses in so much as when one blows it does not need to be replaced as a fuse does. MCB's operate when they sense an overload, or over current, and become an automatic switch, turning off, or tripping, the MCB when it detects such an overload.
An RCD is a similar protective device which is different in two ways. Firstly it is connected to both the live and neutral wires in the consumer unit making it a double pole switch, whereas the MCB is only connected to the live side of the circuit. Secondly, rather than just detecting an overload of current, it detects the fault which causes the overload.
Many consumer units these days are produced to be split load consumer units. See our project on consumer units. Those circuits which need more protection than others, i.e. showers, sockets serving outdoor appliances, external 230V lighting, must be protected by an RCD. Other circuits such as lighting and cookers, are protected by MCB's.
Each individual circuit, of whatever kind, is protected by an MCB. The circuits needing most protection are also served by 1 RCD. Each circuit does not need its own RCD in a split load board.
If you wanted to protect every circuit against overload and faults, you can install an RCBO which is a residual circuit breaker with over current protection. This is a combined MCB and RCD.
Other forms of fuse are either re-wireable fuses and cartridge fuses. Cartridge fuses are simply fuse wire contained in an enclosed glass or ceramic tube (such as the fuse in a plug) and re-wireable fuses (slowly becoming obsolete as wiring regulations are upgraded) which are simply two terminals connected by a length of accessible fuse wire of differing amperage rating.

 

[amberleaf]

The Rules and Regulations Explained :
Regulation 411.3.3.
States that additional protection by means of a 30mA RCD
is to be provided for all socket outlets with a rated current
not exceeding 20A for use by ordinary persons. The only
exceptions allowed are for socket outlets for use under the
supervision of “skilled” or “instructed persons” e.g. some
commercial / industrial locations, or a specific labelled
socket provided for connection of a particular item of equipment, e.g. a freezer circuit.

Regulation 701.411.3.3
In specific locations such as those containing a bath or
shower there is a requirement now to provide RCD
protection on all circuits, including the lighting and shower circuits.

Regulation 314.1 & 2
Requires that every installation shall be divided into
circuits as necessary to avoid danger and minimise
inconvenience, in the event of a fault. Also reducing the
possibility of unwanted RCD tripping, due to excessive
protective conductor currents but not due to an Earth fault.
Separate circuits may be required for parts of the
installation, which need to be separately controlled in such
a way that they are not affected by the failure of other
circuits. The appropriate subdivision should take account
of any danger arising from the failure of a single circuit eg.
an RCD trip on a socket outlet causing the unwanted failure
of a lighting circuit and its associated hazards.

Regulation 522.6.7
Now requires a much greater use of RCD’s to
protect the wiring concealed in walls or partitions even
where installed in previously defined “Safe Zones”.
These regulations effectively mean that all concealed
wiring at a depth of less than 50mm from the surface now
requires protection by a 30mA RCD unless
provided with earthed mechanical protection

The 17th Edition of the IEE wiring regulations ( BS7671 ),
detail a number of regulations relating to protection against electric shock, including the need for additional protection :

The use of RCD's (Residual Current Devices) with a residual operating current not exceeding 30mA is the
recognised means of providing this additional protection in the event of failure of the provision for basic protection
and or the provision for fault protection or carelessness by users :

Such RCD's should not be used to provide the sole means of protection and do not obviate the need to apply one or
more of the recognised protective measure as detailed in the regulations :

Under the new regulations an installation is required to incorporate one or more RCD's, depending upon the
circumstances. Such instances include:-
• All socket outlets not exceeding 20A, but with certain exceptions. One such exception would be permitted for
a specific labelled or otherwise suitably identified socket outlet for connection of a particular piece of equipment.

• Mobile equipment with a current rating not exceeding 32A for use outdoors

• Electrical circuits installed under “Special installations and locations” as defined in Part 7 of the regulations
e.g. Swimming Pools / Saunas.

• All electrical circuits, including shower and lighting circuits etc. in rooms with a fixed bath or shower e.g.
bathrooms and en-suite bedrooms :

In addition to the protection requirements of the outgoing circuits / loads, the requirements of the installed cabling
also must be taken into account :

Where a cable is concealed in a wall or partition at a depth of less than 50mm from the surface, even if installed in the
“safe zone”, if not provided with earthed mechanical protection e.g. Metal trunking or conduit, it must be
provided with additional protection by means of a 30mA RCD :

Whilst it may be desirable to have one or two circuits fed via an unprotected circuit e.g. an identified / dedicated
freezer circuit, the installation of the wiring may still dictate that the circuit must be RCD protected :

The protection of a circuit by means of a 30mA RCD is also required where cables are concealed in walls constructed
with metal stud partitions which are common in modern buildings, irrespective of the depth from the surface,
unless provided with protection in the form of earthed metallic covering, trunking, conduit or other mechanical
protection so as to avoid damage to the cable during installation or construction of the wall :

In Summary :
Regulations : 411.3.3
Relating to : All socket outlets up to 20A rating for general use by ordinary persons :
Example : - Upstairs sockets - Downstairs sockets - Kitchen sockets - Cooker outlet with integral 13A socket outlet
- Plus any other sockets rated up to 20A including garage sockets
Additional Protection : 30mA RCD ,
Regulations : 701.411.3.3
Relating to : All electrical circuits in a room with a fixed bath or shower
Example : - Shower circuit - Lighting circuit - Heating circuit - Ventilation circuit - Shaver socket - Socket outlets ,
Additional Protection : 30mA RCD ,
Regulations : 522.6.6 / 522.6.7 / 522.6.8 /
All electrical circuits buried in a wall or partition at less than 50mm and without mechanical protection
Example : All concealed wiring - Socket outlets - Lighting circuits - Smoke alarm - Burglar alarm
Additional Protection : 30mA RCD ,

Part P Building Regulations : ( 2392-10 Domestic : ) for Customer ,
Please remember when attempting any electrical installations at home that you are obliged to get the completed job tested by a fully qualified electrician and obtain a minor works certificate. Failure to do this may render your house insurance invalid and you may have difficulty selling your home.

 

[amberleaf]

Terms & Conditions : ( this may help self-employed Electricians ) Change some Wording :

:- All material is fully owned by ourselves until invoice is paid off in full, even after installed.

:- Estimates are not fixed quotes and can vary, estimates are approximate minimum-maximum but never a final price.

:- If we do work (including fault finding or cable location etc) then there is a charge and this is not included in free advice.

:- Free advice is general electrical safety recommendations individually to your needs helping to improve the safety of your property/premises.

:- Inspection and testing is included in every invoice as standard (unless specified before work starts) as this is to ensure every circuit worked on complies with current regulations and is safe and fit for use. Sometimes followed with free advice to improve your electrical safety.

:- Inspection and testing is normally including (unless otherwise stated) in all jobs and fully certification given. Certificates are only issued when payment if received in full and all funds have cleared.

:- Duplicate certificates are charged at minimum £ - - per A4 sheet.

:- First invoice is issued and if payment is not received within 10 days (including weekends and bank holidays) a 5% fee is added as late payment and the invoice is resent on day 11 for the extra added amount. Strict 10 days to receive FULL payment, excluding down payments/deposits.

:- Failure to settle account within one calendar month of invoice date will automatically start legal claims proceedings at the FULL rate of invoice. Any discounts / special offers / promotions will be forfeited and reinstated back onto the invoice. All legal costs, late payments fees, additional labour fees can be added to the invoice as decision of Power Plus Electrical. There may be a daily interest applied to any long term outstanding debts until payment cleared in full. Only one reminder is posted as a overdue reminder, this has the 5% added and further to receive payment debt recovery costs started without further warnings.

:- Any equipment requiring hired, i.e. access equipment, other tradesmen (subcontractors, i.e. plumber/builder/carpet fitter/ decorator etc) or any other large cost out with my control will be paid for in advance by yourself the customer (or bill payer) in full before the 1st day of work direct or via ourselves to the subcontractor(s).


:- 1 full years (12 month) guarantee on all parts, labour and any material is included. This does not include access equipment or other trades in guarantee. Lamps, transformers, wear and tear and customer damage/misuse are not included under this clause and chargeable. Any guarantee jobs are only done by ourselves and other contractors services are not refunded.

:- As time, date(s) slot is only agreed when a deposit is paid. A contact is only formed after deposit is received and that time date is arranged, no deposit means no guaranteed start date for work to commence. If work is cancelled without 5 days working notice the deposit is non refundable. More than 5 days prior notice and deposit is fully refundable as long as no material has been ordered. Small jobs normally have no deposit required and can be cancelled at no cost to either party, unless again material is ordered or work has already started. Return materials can have a wholesaler restocking charge.

:- Emergency call out void from a no call out fee, details of call out charge and hourly rate will be explained over the phone. This will vary from job to job , and invoice settled in cash when leaving the property regardless if repaired or return visit required. Return visit is invoiced separately and normally day rates/ costs.

:- Normal working hours at single time are 8am-4:30pm or 9am-5:30pm,, Monday - Friday, including bank holidays, excluding Christmas / New Year. Out with these hours is charged at a higher labour charge.

:- Emergency call out available thought year, 24hour, 365 days a year. (see above).

:- ------- ------- Electrical.co.uk can change its terms and conditions at any time, only in writing if a current contract is already started. No future notice needed to be given to change terms and conditions.

:- Please note that telephone calls are recorded

Fire alarms

Installing a fire alarm is a legal requirement in most commercial and industrial premises Thus alerting of a fire or a smoldering Problem and getting persons and alarm raised quickly. Fire alarms are extremely reliable and with regular testing can be a life- Saving.
Landlords and mains power smoke alarms with battery backup.

Under the common law, Landlords have the duty to ensure the safety of rented property and its contents to Tenants, occupants, neighbors’ or the public do not suffer injury or damage.

The 1991 Smoke Detectors Act, requires that all new houses that have been built since 1992 must, by law, have a smoke detector installed. The minimum requirement being one smoke alarm on each level of the building.

This is not a piece of legislation aimed specifically at residential letting property, but aimed at all new buildings. If an agent installs smoke alarms into properties that he manages or they already exist, care must be taken in ensuring that it is clear

from the letting agreement who is responsible for the maintenance of the detectors including testing and battery replacement.
To neglect this matter could mean that the landlord or agent is responsible, and in the case of a fire could be held liable for being negligent in their duties. There are different rules covering Houses in Multiple Occupation with regard to the installation of smoke detectors and other fire prevention measures.
Installed smoke alarms must be accompanied with a certificate and be tested regularly by pressing the test button. Most landlord insurance requires this certificate and wont payout in the event of a claim. Only qualified electrical contractors can issue this certificate in accordance to BS5839-6.

 

[amberleaf]

Guidance Note 3 , 2392-10 Initial verification , in the context of Regulation 610.1 , is intended to confirm that the installation complies with design and has been
Designed and constructed in accordance with BS-7671 . ( 610.1 – 611.2 – 612.1 ) :
This Section makes recommendations for the initial inspection and testing of electrical installations .
Chapter 61 of BS-7671 states the requirements for “ INITIAL VERIFICATION “ as far as reasonably practicable , ( 611.2 )
An inspection shall be carried out to verify :
(1) All installed electrical equipment and material is of the correct type and complies ( 611.2 ) with applicable British Standards or acceptable equivalents :
(2) All parts of the fixed installation are correctly selected and erected :
(3) No part of the fixed installation is visibly damaged or otherwise defective :

Guidance Note 3 , 2392-10
( 132.14.1 ) Verification of polarity – single-pole device in a ( TN- or TT system )
( 530.3.2 ) it must be verified that single-pole devices for protection or switching are installed in line conductors Only .
Accessories and equipment :
Correct connection ( suitability , polarity , e.t.c ) must be checked . 555 :
Table 55.1 of BS7671 is a schedule of types of plug and socket-outlets available , the ratings , and the associated British Standards :
Particular attention should be paid to the requirements for cable couplers , 553.2
Bayonet lampholders B15 and B22 should comply with BS-EN 61184 and be of ( 559.6.1.7 ) temperature rating ( T2 )

Correct connection ( suitability , polarity , e.t.c ) must be checked . 553 : ← ← ***

The client :
Certificates and reports :
( 631.1 ) Following the initial verification of a new installation or changes to an existing installation ,
( 632.1 ) an Electrical installation Certificate , together with a schedule of inspections and a schedule of test results , is
Required to be given to the person ordering the work , in this context , “ work “ means the installation work , Not the work of carrying out the inspection ( 631.2 ) and Test , Likewise , following the periodic inspection and testing of an existing installation ,
( 634.1 ) a periodic inspection Report , together with a schedule of inspections and a schedule of test results , is required to be given to the person Ordering the inspection :
Sometimes the person Ordering the work is Not the User , in such cases it is Necessary for the User ( e.g. employer or householder ) to have a copy of the inspection and test documentation , it is recommended that those providing documentation to the person Ordering the work recommend that the forms be passed to the User including any purchaser of a Domestic property :

2392-10
Rented Domestic and Residential Accommodation :
In England and Wales , The Landlord and Tenant Act 1985 , Section (11 ) Repairing Obligations in short leases sub-section (1) (b)
Requires a landlord “ to keep in repair and proper working Order the installations in the dwelling-house for the supply of water, gas and Electricity :
A similar requirement can be found in the House ( Scotland ) Act 2006 , Section 13 The repairing standard sub-section (1)(c)
And Section 14 Landlords duty to repair and maintain :
Although neither of the above Acts makes specific mention of a need to carry out Periodic inspection and testing of the electrical installation , they Do place an Obligation on the landlord to maintain the installation in a condition suitable for the use intended :
Where an installation is Not subject to an effective and ongoing planned and proactive maintenance programme , Periodic inspection and testing carried out at appropriate intervals is a practical way of identifying where maintenance work is most required in order to keep the accommodation in a condition that is Safe for use :
Any repairs must be carried out by a competent person , the Landlord is responsible for confirming the competency of any contractors carrying out such work :

2392-10 :
( 2.7.4 ) The sequence of tests : GN-3 ,
Initial tests should be carried out in the following sequence where relevant :
(a) Continuity of protective conductors, including main and supplementary bonding ( 2.7.5 ) Regs , ( 612.2.1 )
(b) Continuity of ring final circuit conductors ( 2.7.6 ) Regs , ( 612.2.2 )
(c) Insulation résistance ( 2.7.7 ) Regs , ( 613.3 )
(d) Protection by SELV,PELV or by electrical separation ( 2.7.9 ) Regs , ( 612.4.1 ) ( 612.4.2 )
(e) Protection by barriers or enclosures provided during erection ( 2.7.9 ) Regs , ( 612.4.5 )
(f) Insulation résistance of Non-conducting floors and walls ( 2.7.10 ) Regs , ( 612.5 )
(g) Polarity ( 2.7.11 ) Regs , ( 612.6 )
(h) Earth electrode résistance ( 2.7.12 ) Regs , ( 612.7 )
(i) Protection by automatic disconnection of the supply ( 2.7.13 ) Regs , ( 612.8 )
(j) Earth fault loop impedance ( 2.7.17 ) Regs , ( 612.9 )
(k) Additional protection ( 2.7.15 ) Regs , ( 612.10 )
(I) Prospective fault current ( 2.7.16 ) Regs , ( 612.11 )
(m) Phase sequence ( 2.7.17 ) Regs , ( 612.12 )
(n) Functional testing ( 2.7.18) Regs , ( 612.13 )
(o) Voltage drop ( 2.7.19 ) Regs , ( 612.612.14

Alterations and Additions :
Every alteration or addition to an existing installation must comply with the Regulations and must Not impair the safety of the existing installation : ( 131.8 – 633.1 – 633.2 )
When inspecting and testing an alteration or addition to an electrical installation , the existing installation must be inspected and tested so far as is necessary to ensure the safety of the alteration or addition . including for example :
* Protective conductor continuity :
* Earth fault loop impedance :
Whilst there is no obligation to inspect and test any part of the existing installation that ( 633.2 ) does not affect and is not affected by the alteration or addition , observed departures are required to be noted in the comments box of electrical installation certificates ( single signature or multiple signature ) and minor works certificates ,

Electrical Installation Certificate :
Regulation ( 631.1 ) of BS-7671 requires that , upon completion of the verification of a new installation , or changes to an existing installation , an Electrical Installation Certificate based on the model given in appendix 6 of BS-7671 shall be provided Section 632 requires that :
(1) the Electrical Installation Certificate be accompanied by a Schedule of Inspections ( 632.1 ) and a Schedule of Test Results.
These Schedules shall be based upon the models given in appendix 6 of BS-7671 :
(2) the Schedule of Test Results shall identify every circuit , including its related protective ( 632.2 ) device(s) , and shall record
The results of the appropriate tests and measurements ; chapter 61 :
(3) the Electrical Installation Certificate shall be compiled Signed / Authenticated by ( 631.4 ) a Competent person or persons
Stating that to the best of their knowledge and ( 632.3 ) belief the installation has been designed , constructed , inspected and
Tested in accordance with BS-7671, any permissible deviations being listed :
(4) any defects or Omissions revealed by the inspector shall be made good and ( 632.4 ) inspected and tested again before
The Electrical Installation Certificate is issued :

 

[amberleaf]

Initial testing :
Introduction to test methods :
The test methods described in this section are the preferred test methods to be used , other appropriate test methods are Not Precluded :
Initial testing :
The test results must be recorded on the Schedule(s) of Test Results and compared ( 631.1 ) with relevant criteria for example , relevant criteria for earth fault loop impedance may be provided by the designer , obtained as described in Section 2.7.14 ↔
( Maximum permissible measured earth fault loop impedance ) Appendix 2 On-Site Guide ←

Protective Conductors :
(1) Cables incorporating protective conductors comply with relevant BS- ( Section 511 )
(2) Joints in metal conduit , duct or trunking comply with Regulations ( 543.3 )
(3) Flexible or pliable conduit to be supplemented by a protective conductor ( 543.2.1 )
(4) Minimum cross sectional area of copper conductors ( 543.1 ) (5) Copper conductors , other than strip, of 6mm2 or less protected by insulation ( 543.3.2 )
(6) Circuit protective conductor at termination of sheathed cables installed with sleeving ( 543.3.2 )
(7) Bare circuit protective conductor protected against mechanical damage and corrosion ( 542.3 and 543.3.1 )
(8) Insulation , sleeving and terminations identified by colour combination green and yellow ( 514.3.1 ) and 514.4.2 )
(9) Joints electrically and mechanically sound ( 526.1 )
(10) Separate circuit protective conductors not less than 4mm2 if not protected against mechanical damage ( 543.1.1 )
(11) Main and supplementary bonding conductors of correct size ( section 544 )

Minor Electrical Installation Works Certificate : GN-3 2392-10
Notes on Completion ,
Scope :
The minor works Certificate is intended to be used for additions and alterations to an installation that do not extend to the provision of new circuit , Example include the addition of a socket-outlet or lighting point to an existing circuit , the relocation of a light switch etc, this Certificate may also be used for replacement of equipment such as accessories or luminaires , but not for the replacement of distribution boards or similar items , appropriate inspection and testing , however , should always be carried out irrespective of the extent of the work undertaken :
Part 1 : Description of minor works :
* 1.2 the minor works must be so described that the work that is the subject of the certification can be readily indentified :
* 4 , see Regulations ( 120.3 ) & ( 120.4 ) No departures are to be expected except in most unusual circumstances , see also Regulations ( 633.1 )
Part 2 Installation details :
* 2 , the method of fault protection must be clearly identified , e.g. Automatic Disconnection of Supply ( ADS ) :
* 4 , if the existing installation lacks either an effective means of earthing or adequate main Equipotential bonding conductors’ ,
This must be clearly stated , see Regulations ( 633.2 ) Recorded departure from BS-7671 may constitute Non-compliance with the Electricity Safety, Quality and Continuity Regulations 2002 ( as amended ) or the Electricity at work Regulations 1989 ,
It is important that the client is advised immediately in writing :
Part 3 : Essential tests :
The relevant provisions of part 6 ( Inspection & Testing ) of BS-7671 must be applied in full to all minor works , for example , where a socket-outlet is added to an existing circuit it is necessary to :-
* 1 , establish that the earthing contact of the socket-outlet is connected to the main earthing terminal :
* 2 , measure the insulation résistance of the circuit that has been added to , and establish that it complies with table 61 of BS-7671 :-
* 3 , measure the Earth fault loop impedance to establish that the maximum permitted disconnection time is not exceeded :-
* 4 , check that the polarity of the socket-outlet is correct :-
* 5 , ( if the work is protected by an RCD ) ← verify the effectiveness of the RCD :-
Part 4 : Declaration :
* 1,3 : the Certificate shall be made out and signed by a competent person in respect of the design , construction , inspection & testing of the work :-
* 1,3 the competent person will have a sound knowledge and experience relevant to the nature of the work undertaken and to the technical standards set down in BS-7671 , be fully versed in the inspection & testing procedures contained in the Regulations and employ adequate testing equipment :-
* 2 , when making out and signing a form on behalf of a company or other business entity , individuals shall state for whom they are acting :-

Protection by barriers or enclosures provided during erection : 3292-10

( 612.4.5 ) this test is not applicable to barriers or enclosures of factory-built equipment , it is
( 416.2.1 ) applicable to those provided on site during the course of assembly or erection and
( 416.2.2 ) therefore is seldom necessary , where , during erection , an enclosure or barrier is
( 416.2.3 ) provided to provide basic protection , a degree of protection not less than IP2X or
( 416.2.4 ) IPXXB is required , Readily accessible horizontal top surfaces must have a degree of protection of at least IP4X or IPXXD :
( 416.2.1 ) the degree of protection afforded by IP2X is defined in BS-EN 60529 as protection against the entry of “fingers or similar objects Not exceeding 80mm in length , solid objects exceeding 12mm in diameter ” the test is made with a metallic standard test finger ( test finger 1 to BS-61032 )
Both joints of the finger may be bent through 90º with respect to the axis of the finger, but in one and the same direction only , the finger is pushed without undue force ( not more than 10 N ) against any openings in the enclosure and , if it enters , it is placed in every possible position ,
A SELV supply, not exceeding 50v , in series with a suitable lamp is connected between the test finger and the live parts inside the enclosure , Conducting parts covered only with varnish or paint , or protected by oxidation or by similar process , must be covered with a metal foil electrically connected to those parts which are normally live in service :
* the protection is satisfactory if the lamp does not light :
The degree of protection afforded by IP4X is defined in BS-EN 60529 as protection ( 416.2.2 ) against the entry of “ wires or strips of thickness grater than 1.0mm , and solid objects exceeding 1.0mm in diameter :
The test is made with a straight rigid steel wire of 1mm + 0.05/0mm diameter applied with a force of 1 N + 10percent ,
The end of the wire must be free from burrs , and at a right angle to its length ,
* the protection is satisfactory if the wire cannot enter the enclosure :
Reference should be made to the appropriate product standard or BS-EN 60529 for a fuller description of the degrees of protection , details of the standard test finger and other aspects of the test ,

Scope :
It is essential that the inspector and the person ordering the inspection know the extent of the installation to be inspected and any criteria regarding the limit of the inspection , both should be agreed and recorded on the Certificate :

Cable :
( 132.7 ) where practicable , the cable size should be assessed against the protective arrangement
( 523 ) based upon information provided by the installation designer ( where available )
( 524 ) :- ( 525 ) Reference should be made , as appropriate , to Appendix 4 of BS—7671 :

Fault Protection :

The methods of fault protection are classified in a number of sub-sections in BS-7671 , and are :
( 411 ) 1 , Automatic disconnection of supply :
( 418.1 ) 2 , Non-conducting location :
( 418.2 ) 3 , Earth-free local Equipotential bonding :
( 413 ) 4 , Electrical separation :

( 411 ) Automatic disconnection of supply ( ADS )

The presence , correct sizing , labelling and connection of appropriate protective conductors must be confirmed as follows :
( 542.3 ) * Earthing Conductor :
( 543 ) * Circuit protective Conductors :
( 544 ) * Protective bonding Conductors :
( 544.1 ) – Main bonding Conductors :
( 544.2 ) – Supplementary bonding Conductors :

Sockets-Outlets : 2392-10
1 , Complies with BS-196 , BS- 546 , BS- 1363 , BS- EN 60309-2 ) and shuttered for household and similar installations ( 553.1.4 )
2 , Mounting height above the floor or working surface suitable ( 553.1.6 )
3 , Correct Polarity ( 612.6 )
4 , if installed in a location containing a bath or shower , installed beyond 3m horizontally of the bath or shower unless shaver supply unit or SELV ( 701.512.3 )
5 , Protected where mounted in a floor ( Section 522 )
6 , Not used to supply a water heater having uninsulated elements ( 554.3.3 )
7 , Circuit protective conductor connected directly to the earthing terminal of the Socket-Outlet , on a sheathed wiring installation ( 543.2.7 )
8 , Earhing tail from the earthed metal box , on a conduit installation to the earthing terminal of the Socket-Outlet ( 543.2.7 )

Joint box :

1 , Joint accessible for inspection ( 526.3 )
2 , Joints protected against mechanical damage ( 526.7 )
3 , All conductors correctly connected ( 526.1 )

Fused Connection Unit :
1 , Correct rating and fuse ( 533.1 )
2 , Complies with BS-1363-4 ( 559.6.1.1 vii )

Cooker Control Unit :
1 , Sited to one side and low enough for accessibility and to prevent flexes trailing across radiant plates ( 522.2.1 )
2 , Cable to cooker fixed to prevent strain on connections ( 522.8.5 )

 

[amberleaf]

Phase Rotation Instruments : ( 612.12 )

BS-EN 61557-7 gives the requirements for measuring equipment for testing the Phase Sequence in Three-Phase distribution Systems whether indication is given by mechanical , visual and / or audible means :
BS-EN 61557-7 includes requirements that :
* Indication shall be unambiguous between 85 per cent and 110 per cent of the nominal system voltage or within the range of the nominal voltage and between 95 per cent and 105 per cent of the nominal system frequency :
* the measuring equipment should be suitable for continuous operation :
* the measuring equipment should be so designed that when either one or two measuring leads are connected to earth and the remaining measuring lead(s) remain connected to their corresponding Phase conductors , the resulting total current to earth should not exceed 3.5 mA rms :
* the measuring equipment should not be damaged nor should the user be exposed to danger in situations where the measuring equipment is connected to 120 per cent of the rated system voltage or to 120 per cent of its rated maximum voltage range :
* Portable measuring equipment should be provided with permanently attached leads or with a plug device with live parts not accessible , whether plugged or unplugged :

RCD Testers :
The test instrument should be capable of applying the full range of test current to an in-service accuracy as given in BS-EN 61557-6 , this in-service reading accuracy will include the effects of voltage variations around the nominal voltage of the tester ,
To check RCD operation and to minimise danger during the test , the test current should be applied for no longer than ( 2sec )
* instruments conforming to BS-EN 61557-6 will fulfil the above requirements : ( 612.1 )

Operation of overcurrent circuit-breakers :

( 612.13.2 ) where protection against overcurrent is provided by circuit-breakers , the manual operating mechanism of each
circuit-breaker should be operated to verify that the device opens and closes satisfactorily :
( 611.3 ( viii ) it is not normally necessary or practicable to test the operation of the automatic tripping mechanism of circuit-breakers
.any such test would need to be made at a current substantially exceeding the minimum tripping current ii order to achieve operation within a reasonable time , for circuit-breakers to BS-EN 60898 a test current of not less than two and a half times the nominal rated tripping current of the device is needed for operation within 1 minute , and much larger test currents are necessary to verify operation of the mechanism for instantaneous tripping :

For circuit-breakers of the sealed type , designed not to be maintained , if there is doubt above the integrity of the automatic mechanism it will normally be more convenient to replace the device than to make further tests , such doubt may arise from visual inspection , if the device appears to have suffered damage or undue deterioration , or where there is evidence that the device may have failed to operate satisfactorily in service :

circuit-breakers with the facility for injection testing should be so tested and , if appropriate , relay settings confirmed :

GN-3

The Requirements of the Electricity at Work Regulations 1989 must be taken into account when considering the use of thermographic surveying Equipment as its use may necessitate the temporary removal or bypassing of measures that provide basic protection ( as defined in BS-7671 ) such as opening doors to electrical panels and the removal of barriers and covers ,
The Requirements of Regulation 14 ( Work on or near live conductors ) which is reproduced below , are particularly pertinent :

No person shall be engaged in any work activity on or so near any live conductor ( other than one suitably covered with insulating material so as to prevent danger ) that danger may arise unless :-

(a) it is unreasonable in all the circumstances for it to be dead ; and
(b) it is reasonable in all the circumstances for him to be at work on or near it while it is live ; and
(c) suitable precautions ( including where necessary the provision of suitable protective equipment ) are taken to prevent injury ,

Thermographic Surveying :

Important Note : it is recommended that persons refer to the Requirements of the Electricity at Work Regulations 1989
And the guidance given in the Memorandum of Guidance on the Electricity at Work Regulations 1989 ( HSR25 )
Prior to undertaking any work activity which places themselves or those under their control in close proximity to live parts :

External Influences : 2391 -
( 611.2 ) any known changes in external influences , building structure , and alterations or additions which may have affected the suitability of the wiring for its present load and method of installation should be Noted .

Note should also be made of any alterations or additions of an irregular nature to the installation ,
If unsuitable material has been used , the report should indicate this together with reference to any evident faulty workmanship or design ,

Required Competence :

( 610.1 ) the inspector carrying out the inspection and testing of any electrical installation must ,
( 610.5 ) as appropriate to his or her function , have a sound knowledge and experience relevant to
( 611 ) the nature of the installation being inspected and tested , and to the technical standards ,
The inspector must also be fully versed in the inspection and testing procedures and employ suitable testing equipment
During the inspection and testing process ,

It is the Responsibility of the inspector to :

( 610.1 ) (1) ensure no danger occurs to any person or livestock and property in not damaged :
( 612.1 ) (2) compare the inspection and testing results with the design criteria :
(3) take a view on the condition of the installation and advise on remedial works :

( 634.2 ) in the event of a dangerous situation being found , the inspector should recommend the immediate isolation of the defective part , the person ordering the work should be informed of this recommendation without delay :

 

[amberleaf]

Enclosures and mechanical protection :
( 612.4.5 ) the Enclosures and mechanical protection of all electrical equipment should be
( 132.5 ) inspected to ensure that they remain adequate for the type of protection intended , all
( 611.3 ( xiii ) secondary barriers ( to IP2X or IPXXB ) should be in place ,
( 416.2.4 )

Polarity : ( 612.6 ) GN-3 2.7.11

Tests should be made to verify that :
(1) the polarity is correct at the meter and distribution board :
(2) every fuse and single-pole control and protective devices are connected in line ( 612.6 ) conductors’ only :
(3) conductors’ are correctly connected to socket-outlets and other accessories / equipment
(4) except for E14 and E27 lampholders to BS-EN 60238 , centre-contact bayonet and Edison screw lampholders
Have their outer or screw contacts connected to the Neutral conductor :
(5) all multi-pole devices are correctly installed :

It should be established whether there have been any alterations or additions to the installation since its last inspection
And test , if there have been no alterations or additions then sample tests should be made of at least 10 per cent of all single-pole and multi-pole control devices and of any centre-contact lampholders , together with 100 per cent of socket-outlets ,
If any incorrect polarity is found then a full test should be made in that part of the installation supplied by the particular distribution board concerned , and the sample testing increased to 25 per cent for the remainder of the installation , if additional cases of incorrect polarity are found in the 25 per cent sample ,
A full test of the complete installation should be made :

Earth Electrode Résistance Testers :

This may be a four-terminal instrument ( or a three- terminal one where a combined lead to the earth electrode would not
Have a significant résistance compared with the electrode résistance ) so that the résistance of the test leads and temporary spike
Résistance can be eliminated from the test result ,

Aspect affecting in-service reading accuracy include the effects of temporary spike résistance ,
Interference currents and the layout of the test electrodes , the instrument should carry some facility to check that the résistance
To earth of the temporary potential and current spikes are within the operating limits of the instrument ,
It may be helpful to note that instruments complying with BS-EN 61557-5 incorporate this facility , care should be exercised to ensure that temporary spikes are positioned with reasonable accuracy :

2392-10

Initial Verification :

Purpose of initial verification :
initial verification , in the context of Regulation ( 610.1 ) is intended to confirm that the ( 610.1 )
installation complies with the design and has been designed and constructed in ( 611.2 )
accordance with BS-7671 ( 612.1 )

this section makes recommendations for the initial inspection and testing of electrical installations :

Chapter 61 of BS-7671 : states the requirements for “ Initial Verification “ as far as ( 611.2 )
Reasonably practicable , an inspection shall be carried out to verify :

(1) all installed electrical equipment and material is of the correct type and complies ( 611.2 )
With applicable British Standards or acceptable equivalents :
(2) all parts of the fixed installation are correctly selected and erected :
(3) no part of the fixed installation is visibly damaged or otherwise defective :

Inspections : ( 611. )
Inspection is an important element of inspection and testing ,
Initial Inspection :
General procedure :
Inspection and , where appropriate , testing should be carried out and recorded on suitable schedules progressively throughout the different stages of erection and before the installation is certified and put into service , Comments on Individual items to be Inspected :
The inspection should include at least the checking of those items listed in Section ( 611.3 ) of BS-7671 :
Tests : ( 612. )
Initial testing : introduction to test methods : the test methods described in this section are the preferred test methods to be used ;
Other appropriate test methods are not precluded ,
Initial testing :
The test results must be recorded on the Schedule(s) of Test Results and compared ( 612.1 ) with relevant criteria .
For example , relevant criteria for earth fault loop impedance may be provided by the designer , obtained as described in section 2.7.14 GN-3 :
Earth fault loop impedance :
Determining the earth fault loop impedance , ( Ze )
The earth fault current loop comprises the following elements , starting at the point of fault on the ↔ ( Line-Earth loop ) :
* the circuit protective conductor :
* the main earthing terminal and earthing conductor :
* for TN-Systems the metallic return part or , in the case of TT and IT systems , the earth return path :
* the part through the earthed neutral point of the transformer :
* the source line winding : and
* the line conductor from the source to the point of fault :

Earth fault loop impedance ( Zs ) may be determined by : ( 612.9 ) ↔ ( 612.8 )
(1) measurement of ( R1 + R2 ) during continuity testing and adding to ( Ze ) i.e. Table 41.2 : Table 41.3 : Table 41.4 :
( Zs = Ze + ( R1 + R2 )
( Ze ) is determined by :
* measurement ( see below ) , or
* enquiry of the electricity supplier , or
* calculation , or

(2) direct measurement using an earth fault loop impedance tester ( see below )

Determining ( Ze )
Measurement :

The reasons that ( Ze ) is required to be measured are twofold :

(1) to verify that there is an earth connection :
(2) to verify that the ( Ze ) value is equal to or less than the value determined by the designer and used in the design calculations :

( Ze ) is measured using an earth fault loop impedance tester at the origin of the installation :

( 542.4.2 ) the impedance measurement is made between the ( Line of the supply ) and the means of earthing with the mains switch open or
With all the circuits isolated , the means of earthing must be disconnected from the installation earthed equipotential bonding for ( 610.1 )
The duration of the test to remove Parallel paths , care should be taken to avoid any shock hazard to the testing personnel and other persons on the site both whilst establishing contact , and performing the test : ENSURE THAT THE EARTH CONNECTION HAS BEEN REPLACED BEFORE RECLOSING THE MAIN SWITCH :

Main switch ( Open ) :
Test of ( Ze ) at the Origin of the Installation :

Measurement of ( R1 +R2 ) to add to ( Ze )
Whilst testing the continuity of the protective conductors of Radial Circuits , or whilst testing the Continuity of ring final circuits , the value of
( R1 +R2 ) test ; is measured ( at the test ambient temperature )

The measured value of ( R1 +R2 ) test ; for the final circuit should be added to the value of ( R1 +R2 ) test ; for any distribution circuit supplying the final circuit , to give the total ( R1 +R2 ) test ; from the origin of the installation :

Direct measurement of ( Zs )
Direct measurement of ( Zs ) can only be made on a LIVE INSTALLATION ,
Neither the connection with earth nor bonding conductors are disconnected Readings given by the loop impedance tester may be less than Ze + ( R1 +R2 ) because of PARALLEL EARTH RETURNPATHS provided by any bonding extraneous-conductive-parts ,
This must be taken into account when comparing the results with design data :

Care should be taken during the tests to avoid any shock hazard to the testing personnel , other persons or livestock on site :

Enquiry :
Where ( Ze ) is determined by enquiry of the electricity supplier , ( Zs ) is then determined by adding ( R1 +R2 ) to this value of ( Ze )
However , a test must be made to ensure that the electricity suppliers earth terminal is actually connected with earth , using an earth fault loop impedance tester or a test lamp :

Verification of test results :
Values of ( Zs ) should be compared with one of the following ( 612.1 ) :
(1) for standard thermoplastic ( PVC ) circuits :
(2) earth fault loop impedance figures provided by the designer : table 41.2 )
(3) tabulated values in BS-7671 , corrected for temperature : table 41.3 )
(4) rule-of-thumb figures : table 41.4 )
Appx 14 :

 

[amberleaf]

Earth fault Loop impedance test voltage :

The normal method of test employed by a line-earth loop tester is to compare the unloaded loop circuit voltage with the circuit voltage when loaded with a low résistance , typically 10Ω this method of test can create an electric shock hazard if the line-earth loop impedance is high and the test duration is not limited , in these circumstances the potential of the protective conductor could approach line voltage for the duration of the test :

Earth fault Loop impedance testers :
These instruments operate by circulating a current from line conductor into the protective earth ,
This will raise the potential of the protective earth systems :
To minimise electric shock hazard from the potential of the protective conductor ,
The test duration should be within safe limits , this means that the instrument should cut of the test current after 40 ms or a time determined by the safety limits derived from the information contained within DD IEC/TS 60479-1 ,
If the voltage rise of the protective conductor exceeds 50v during the test :

Instrument accuracy decreases as scale reading reduces , aspects affecting in-service reading accuracy include transient variations of mains voltage during the test period , mains interference , test lead résistance and errors in impedance measurement as a result of the test method , to allow for the effect of transient voltages the test should be repeated at least once , the other effects cannot be eliminated by test procedures :

For circuits rated up to 50A , a line-earth loop tester with a resolution of 0.01Ω should be adequate , in general , such instruments can be relied upon to be accurate down to values of around 0.2Ω :

Instruments conforming to BS-EN 61557-3 . will fulfil the above requirements :

These instruments may also offer additional facilities for deriving prospective short-circuit current , the basic measuring principle ids generally the same as for earth fault loop impedance testers . the current is calculated by dividing the earth fault loop impedance value into the mains voltage . instrument accuracy is determined by the same factors as for loop testers . in this case , instrument accuracy decreases as scale reading increases , because the loop value id divided into the mains voltage , it is important to note these aspects , and the manufacturers documentation should be referred to :

Test Instruments : GN-3

Instruments standard :
BS-EN 61010 Safety Requirements for Electrical Equipment for Measurement Control and Laboratory use is basic safety standard for electrical test instruments ,

The basic instrument standard is BS-EN 61557 Electrical Safety in Low Voltage Distribution Systems up to 1000V a.c and 1500V d.c
Equipment for testing , measuring or monitoring of protective measures , this standard includes performance requirements and requires compliance with BS-EN 61010 :

Reference was made to the use of test leads which conform to HSE Guidance Note GS-38 , the safety measures and procedures set out in HSE Guidance Note GN-38 SHOULD BE OBSERVED FOR ALL INSTRUMENTS , LEADS , PROBES AND ACCESSORIES , IT SHOULD BE NOTED THAT SOME TEST INSTRUMENT MANUFACTURERS advise that their instruments be used in conjunction with fused test leads and probes . Other manufacturers advise the use of non-fused leads and probes when the instrument has in-built electrical protection , but it should be noted that such electrical protection does not extend to the probes and leads :

Routine checks :

Electrical Installations should not be left without any attention for the periods of years that are normally allowed between formal inspections ,
In domestic premises it is presumed that the occupier will soon notice any breakages or excessive wear and arrange for precautions to be
Taken and repairs to be carried out . in other situations , there must be arrangements made for initiating reports of wear and tear from users of the premises , this should be supplemented by routine checks , the frequency of these checks will depend entirely upon the nature of the premises , routine checks would typically include :

Activity : ………………………………………… Checks :
Defects reports : …………………………………. All reported defects have been rectified
Inspection : ………………………………………. Look for : ↔ ( breakages ) ( wear/deterioration ) ( signs of overheating )
( missing parts ( covers , screws ) ( loose fixings )

* confirm :
Switchgear accessible ( not obstructed )
Doors of enclosures secure : adequate labelling in place :

Operation …………………………………………. Operate :
…………………………………………………….. switchgear ( where reasonable )
…………………………………………………….. equipment – switch on and off
…………………………………………………….. including RCDs ( using test button )

These routine checks need not be carried out by an Electrically Skilled Person but should be done be somebody who is able to safely use the installation and recognise defects :

Periodic Inspection Report :

BS-7671 requires that the result and extent of periodic inspection and testing shall ( 631.2 ) be recorded on a periodic inspection
Report and provided to the person ordering the ( 634.1 ) inspection :

The report must include : ( 631.1 )
(1) a description of the extent of the work , including the parts of the installation inspected and details of what the inspection
And covered :
(2) any limitations which may have been imposed during the inspection and testing of the installation :
(3) details of any damage , deterioration , defects and dangerous conditions and any ( 634.2 ) non-compliance with BS-7671
Which may give rise to danger :
(4) Schedule of inspections :
(5) Schedule of test results :

Any immediately dangerous condition should preferably be rectified , if Not , the defect should be reported in writing without delay to the employer or responsible employee ( see Regulation 3 of the Electricity at Work Regulations 1989 )

( 621.2 ) installations including those constructed in accordance with earlier editions of BS-7671 should be inspected and tested
For compliance with the current Edition of BS-7671 and departures recorded , however , reference should be made to the note by the Health and Safety Executive following the preface to BS-7671 , that installations conforming to earlier editions and not
Complying with the current Edition do not necessarily fail to achieve conformity with the Electricity at Work Regulations 1989 ,

Guidance on the action to be taken is to be given in the Observations and Recommendations section of the Periodic Inspection Report by Numbering each observation ( non-compliance ) ( 1 ) to ( 4 )

If the number ( 1 ) is allocated to an Observation , indicating that it requires urgent attention ,
Then the overall assessment must be that it is unsatisfactory ,
An example of this is an installation which has no earth , if numbers ( 2 ) or (3 ) are allocated , the person carrying out the test
Will have to use judgement to determine whether or not the installation can be classed as Satisfactory :

Where an “ ( X ) “ ( unsatisfactory ) observation has been recorded against any item in the Schedule of inspections ,
A corresponding comment should be included in the “ Observations and Recommendations Section :

Insulation testing: A guide to getting it right : Apprentices’ :

The insulation test performs a measurement of the resistance of a product's insulation protection by applying a DC voltage between phase and neutral to the earth conductor for Class I equipment; and between phase and neutral to the outer case for Class II equipment. The test results in a reading of resistance measured in M ohms.

So why is it necessary to carry out the test? The test is designed to ensure that protective insulation is sufficient good enough to form a barrier to make sure that electricity does not come into contact with a user causing harm or to ensure that other manufacturing systems and machinery are not adversely affected.

So why is it necessary to carry out the test ? The test is designed to ensure that protective insulation is sufficient good enough to form a barrier to make sure that electricity does not come into contact with a user causing harm or to ensure that other manufacturing systems and machinery are not adversely affected.

In the manufacturing environment, the advent of legalisation such as the Low Voltage Directive (LVD) requires evidence of due diligence and the results of this and other tests can be used in this respect. The same can be said of in-service testing too.

Testing conditions : Regs : table 61
The test can be applied to both Class I and Class II equipment. The test should be carried out using probes or insulted clips, and without the equipment being connected to a power supply. Test voltages vary between standards - although 500V DC is the most common application - and the voltage is applied for a maximum of three seconds.

“ Dead Test “
Insulation Résistance Test Instrument , ( MΩ )
Capable of Supplying the Test Voltage D.C. Indicated in ( Table 61 )
Single-Phase Installation ( Line ↔( Live ) to Neutral ) L1 / N1 :

Red Lead / Line ↔( Live ) – Neutral : Black Lead / Earth : ( 2 – Leads Only )

( Line 1 – Brown :
( Line 2 – Black :
( Line 3 – Gray :
( N1 – Blue :

Three-Phase installation : ( 3-leads or 4-leads )
Phase ( L1 and L3 ) ← Brown / Gray
Phase ( L1 and L2 ) ← Brown / Black
Phase ( L2 and L3 ) ← Black / Gray

Test each Line in Turn to the Neutral

Three-Phase installation : ( NICEIC )
Line ( L1 to Line 2 ) Brown / Black
Line ( L2 to Line 3 ) Black / Gray
Line ( L3 to Line 1 ) Gray / Brown

Then Test each Line in turn to the Neutral :

* Insulation Résistance is Measured Between Live Conductors ( Line & Neutral ) CPC :
Single-Phase Installation :

 

[amberleaf]

Given my issue is with Earth , how do I Test that Earth ? Apprentices’

I understand the Basic Principles of using a Mulitmeter on a simple Circuit ( i.e. Testing for current in Series , for volt diffences in Parallel )
If I was Testing voltage in the Live , and I had a good Earth , or I was measure voltage across the Bulb , that would be easy .
But in the case of my Earth problem at the Switch , what do I need to Test : ?

You are worried about voltage on the Earth Conductor of the Lighting Circuit , for a start , Measure Voltage ( P-N . N-E . P-E )
Then put a bulb into on the Circuit , switch it on , and Measure them all again

Then take out all bulbs , turn OFF at the Mains switch , and Measure ( Lowest Ohms Range ) Résistances between them all :
Then Main Switch back on , and Measure Résistance ( N-E / Only :
You will be able to see what’s happening then , ( Get Measuring with Meter Ω )

Insulation Résistance Ohmmeters :

The instrument used should be capable of developing the test voltage required across the Load , The Test Voltage Required is : ( Table 61 ) (1) 250V d.c for SELV and PELV circuits : (2) 500V d.c for all Circuits rated up to and including 500V , but excluding Extra-Low voltage circuits mentioned above : (3) 1000V d.c for all Circuits rated above 500V up to 1000V
Instruments conforming to BS-EN 61557-2 will fulfil all the above instrument requirements :
The factors affecting in-service reading accuracy include 50Hz currents induced into cables under test , and capacitance in the test object , these errors cannot be eliminated by test procedures , capacitance may be as high as 5 uf , and the instrument should have an automatic discharge facility capable of safely discharging such a capacitance , Following an Insulation Résistance test , the instrument should be left connected until the capacitance within the installation has fully discharged ,

 

[amberleaf]

Insulated Cables :

Non-Flexible Cables :
1, Correct type ( 521 ) :
2, Correct current rating ( 523 ) :
3, Protected against mechanical damage and abrasion ( 522.8 ) :
4, Cables suitable for high or low ambient temperature as necessary ( 522.1 ) :
5, Non-sheathed cables protected by enclosure in conduit , duct or trunking ( 521.10 ) :
Sheathed cables :
* Routed in allowed zones or mechanical protection provided ( 522.6.6 ) :
* in the case of domestic or similar installations not under the supervision of skilled or instructed persons , additional protection is provided by RCD having ( I∆n ) not exceeding 30mA ( 522.6.7 ) :
7, Cables in partitions containing metallic structural parts in domestic or similar installations not under the supervision of skilled or
Instructed persons should be / ↔ provided with adequate mechanical protection to suit both the installation of the cable and its normal use / ↔ provided with additional protection by RCD having (I∆n ) not exceeding 30mA ( 522.6.8 ) :
8, where exposed to direct sunlight , of a suitable type ( 522.11 ) :
9, not run in lift shat unless part of the lift installation and of the permitted type ( BS-5655 and BS-EN 81-1 ( 528.3.5 ):
10, buried cable correctly selected and installed for use ( 522.6.4 ) :
11, correctly selected and installed for use overhead ( 521 ) :
12, internal radii of bends not sufficiently tight as to cause damage to cables or to place undue stress on terminations to which they are connected ( relevant BS , BS-EN and 522.8.3 ) :
13, correctly supported ( 522.8.4 and 522.8.5 ) :
14, not exposed to water , etc, unless suitable for such exposure ( 522.3 ) :
15, metal sheaths and armour earthed ( 411.3.1.1 ) :
16, identified at terminations (514.3 ) :
17, joints and connections electrically and mechanically sound and adequately insulated ( 526.1 and 526.2 ) :
18, all wires securely contained in terminals , etc. without strain ( 522.8.5 and section 526 ) :
19, enclosure of terminals ( section 526 ) :
20, glands correctly selected and fitted with shrouds and supplementary earth tags as necessary ( 526.1 ) :
21, joints and connections mechanically sound and accessible for inspection , except as permitted otherwise ( 526.1 and 526.3 ) :

PELV :

PELV ( protective extra-low voltage ) installations are inspected and tested as for SELV ( 612.4.2 )
Installations except that an insulation test is not made between PELV circuits and ( 414.4.1 ) Earth :

( PELV systems may include a protective conductor connected to the protective conductor of the primary circuit , basic protection in the secondary circuit is dependent upon the primary circuit protection )

Functional extra-low voltage :
extra-low voltage circuits not meeting the requirements for SELV or PELV are inspected ( 612.4.4 ) and tested as low voltage circuits :

Electrical Separation :
The source of supply should be inspected to confirm compliance with Regulations , ( 612.4.3 ) in addition ,
Should any doubt exist , the voltage should be measured to verify it does ( 413.3.2 ) not exceed 500v ,

The insulation between live parts of the separated circuit and any other adjacent ( 612.4.3 ) in addition ,
Conductor ( in the same enclosure or touching ) and /or to earth , must be tested , this test should be performed at a voltage of 500v dc , and the insulation résistance should be not less than 1.0MΩ ,

Instrument : use an insulation résistance tester for this test :

The live parts of the separated circuit must be tested to ensure that they are electrically ( 413.3.2 ) separate from other circuits ,
This is achieved by testing between the live conductors of the separated circuit connected together and the conductors of any other adjacent circuit strapped together :

The first test applied to this arrangement is an insulation résistance test at 500v dc the insulation résistance should be not less than 1.0MΩ :

Instrument : use an insulation résistance tester for this test :

( 413.3.5 ) A separate wiring system is preferred for electrical separation , if multicore cables or insulated cables in insulated conduit are used , all cables must be insulated to the highest voltage present and each circuit must be protected against overcurrent ,

( 612.4.3 ) A 500v dc , insulation résistance test is performed between the exposed-conductive- ( 413.3.3 ) parts of any item of connected equipment , and the protective conductor or exposed-conductive-parts of any other circuit , to confirm compliance with the Regulations , the insulation résistance should be not less than 1.0MΩ

Instrument : use an insulation résistance tester for this test :

 

[amberleaf]

NEW OR REWIRED DOMESTIC AND SIMILAR INSTALLATIONS : Apprentices’

* Does the 17th Edition require all 13 A socket-outlets in domestic premises to be RCD-protected ?
For new installations and rewires in domestic premises, all socket-outlets need to have additional protection by RCD, except perhaps for those intended to supply particular items of equipment such as freezers. Any socket-outlet not having RCD protection needs to be specifically labelled or otherwise suitably identified to indicate its intended use, such as ‘freezer only’. However, if the wiring to a dedicated socket-outlet is concealed in a wall or partition at a depth of less than 50 mm, or if the internal construction of the wall or partition includes metallic parts other than metallic fixings, the circuit will still need to be suitably protected (by RCD or other means). Regulation Numbers : 411.3.3 (522.6.6) (522.6.8 )
*The 17th Edition requires most if not all circuits in domestic premises to be RCD-protected. There have been a number of suggestions as to how the consumer unit may best be configured to comply with the Regulations, the most common being a main switch with RCBOs protecting each individual circuit. However, another suggestion favours a main switch with two RCDs protecting separate DIN rails. If careful consideration is given as to what each bar will control in the way of upstairs and downstairs lighting and power circuits, will this configuration comply?
Yes, as long as the division of final circuits between the RCDs is carefully considered so as to minimize the consequences of unwanted tripping. Separate RCD protection is not necessarily required for each circuit of an installation but, in order to minimize the likelihood and consequences of tripping, a single (‘front end’) RCD should not be used to protect all the circuits. Regulation Numbers : ( 314.1 )
* The 17th Edition does not now define a zone 3 in a bathroom or shower room. What electrical equipment and accessories can be installed in the area between 0.6 m and 3.0 m from the edge of the bath or shower basin? Moreover, what minimum degree of IP protection are manufacturers likely to recommend?
There is no change from the 16th Edition requirements – that is, the general rules apply. The manufacturer’s installation instructions must always be followed. Regulation Numbers : ( 512.2 ) ( 134.1.1 )
* Do ‘meter tails’ concealed in walls or partitions need to be protected in accordance with Regulations 522.6.6 and/or 522.6.8 ?
* Yes. Meter tails concealed in a wall or partition at a depth of less than 50 mm from a surface must be protected in accordance with Regulation 522.6.6. Also, irrespective of the depth from a surface, meter tails concealed in a wall or partition having internal metallic parts (except nails and screws, etc) are subject to the requirements of Regulation 522.6.8. Regulation Numbers : 522.6.6: 522.6.8 : 314.1: 314.2 :
However, additional protection for meter tails by means of an RCD is not an acceptable option in respect of Regulation 522.6.7 (which in consequence rules out reliance on 522.6.6(v), routing in the ‘safe zones’ alone), or in respect of Regulation 522.6.8(v). Also, for TT systems, the only option remaining is to provide suitable mechanical protection (that is, to comply with Regulations 522.6.8(iv) and/or 522.6.6(iv) as appropriate).
* Where the Regulations specify additional protection by RCD, does this include RCBOs ?
Yes. Where the generic term ‘RCD’ is used, it refers to most types of residual current device including RCBOs (Residual current-operated circuit-breakers with integral overcurrent protection), RCCBs (Residual current-operated circuit-breakers without integral overcurrent protection) and SRCDs (Socket-outlets incorporating a residual current device). For the purposes of the Regulations, it does not include PRCDs (Portable residual current devices). 411.3.3

• Does boiler pipework need to have additional equipotential bonding for electrical safety reasons ?
There is no specific requirement in the Regulations for boiler pipework to be supplementary bonded. However, such bonding may be called for in the boiler manufacturer’s instructions, in which case BS 7671 requires those instructions to be followed (Regulation 510.2 refers). Any stated requirement for additional bonding that is considered to be unnecessary should be queried with the manufacturer concerned, and amended installation instructions requested. Regulation Numbers : 411.3.3
* Does the dispensation in Regulation 701.415.2 to omit supplementary bonding in a location containing a bath or shower apply to TT systems? Yes Regulation Numbers : 701.415.2
* If the mains supply cable to a fixed appliance such as a flat screen TV is concealed in a wall or partition at a depth of less than 50 mm, does the 17th Edition require the lead to be RCD-protected in accordance with Regulation 522.6.7 even though it’s connected by means of a plug and socket ?
Yes. The risk of penetration by a nail or screw is the same as for other concealed cable. Also, if the wall or partition has internal metallic parts (except nails and screws, etc), RCD protection in accordance with Regulation 522.6.8 is required irrespective of the depth of the cable from the surfaces. Regulation Numbers : 522.6.7, 522.6.8
* To overcome thermal insulation issues, is it permissible to design a ring final circuit using 2.5 mm² cable protected by a 20 A protective device?
Yes, if the effective current carrying capacity of the cable is at least 12.5 A (20 A × 20/32), so as to effectively have the same ‘deemed to comply status’ as Regulation 433.1.5 gives to 30 A and 32 A ring final circuits. 433.1.5
* What types of mechanical protection provide sufficient protection against penetration by nails, screws and the like ?
As an example, steel of 3 mm minimum thickness is generally considered to provide sufficient mechanical protection, except where shot-fired nails are likely to be used. 522.6.6 : 522.6.8 :

* Five flats are fed individually from five ‘sub-mains’ originating at the main intake position. The five gas and water meters are main bonded at the main intake position. Do we still need to provide main bonding in each of the flats?
Whilst main protective bonding is required at the main intake position, it is good practice also to provide main protective bonding in each flat even though, in this case, the origin of each installation could be considered to be at the main intake position. Regulation Numbers : 411.3.1.2
* Is an RCD main switch (such as a 100 mA time-delayed device) still required in the consumer unit of a new domestic installation forming part of a TT system?
For a domestic installation complying with the 17th Edition where all the final circuits are RCD-protected, an RCD main switch is no longer required, provided that the consumer unit is of all insulated construction.
*Does the device that has to be provided for switching off a bathroom extract fan for mechanical maintenance need to be located adjacent to the fan ?
No, but the device does need to be so placed and marked as to be readily identifiable and convenient for the intended use 537.3.2.4
* Does the 17th Edition permit connection of smoke alarms to an adjacent lighting circuit taking into account Regulation 560.7.1, which states that circuits of safety services shall be independent of other circuits?
Yes. The particular requirements of BS 5839-6 take precedence over the general requirements of BS 7671. 110.1
* Does the R1 + R2 test confirm& the correct polarity of a radial circuit ?
No, not on its own. Whilst the test can provide an indication of polarity, it needs to be combined with inspection and further testing as required by Part 6 of BS 7671: 2008 ( 611.3, 612.6 )
* Appendix 15 of BS 7671: 2008 gives advice on ring final circuits and sharing/spreading the load around the circuit. Item (iii) suggests that cookers, ovens and hobs over 2 kW should be on their own dedicated circuit. Why can’t ovens of less than 3 kW be connected to a ring final circuit via a suitable connection point such as a socket-outlet or fused connection unit?
Appendix 15 is intended to give guidance only. Such connection is not prohibited, provided that no part of the ring final circuit will be overloaded as a result. 433.1.5 :
*Is it necessary to verify voltage drop during initial verification ?
Verification of voltage drop is not normally required unless there is considered to be a voltage drop problem. 612.14
* Considering Regulations 134.1.1 and 510.2 which require equipment to be installed in accordance with instructions provided by the manufacturer, are installers now required to check torque settings for connection tightness at consumer units where these are manufacturers instructions.
Yes. It is necessary to check that all connections are tight, and any specific installation instructions must also be followed.

 

[amberleaf]

*In a location containing a shower, what is the horizontal limit of zone 1 for showers without a basin?
The limit of zone 1 horizontally is 1.2 m from the centre point of the fixed water outlet (the end of the rigid pipe of the fixed water installation) on the wall or ceiling, irrespective of whether the shower head is fixed or on the end of a flexible hose. Beyond zone 1, the general rules of BS 7671 apply, including Regulation 512.2 concerning external influences. In particular, the IP rating of any electrical equipment must be adequate. 701.32.4 : 512.2 :

Regulation 560.7.7 requires cables for safety circuits, other than metallic screened fire-resistant cables, to be adequately and reliably separated from other circuit cables. In addition to mineral insulated cables, what cables would be exempted from this separation requirement ? (560.7.7 )
Soft-skinned cables to BS 7629-1: 2008 would be exempted from the separation requirements as they have a metallic screen and their survival in a fire has been tested in accordance with BS EN 50200. However, cables to BS 8436: 2004 would not be exempted as the product standard does not require their fire resistance to be tested. Irrespective of the above, BS 5839-1 recommends that, for a fire detection and alarm system complying with that standard, the circuits of fire alarm systems should be segregated from the cables of other circuits to minimize the potential for those other circuits to cause malfunction of the fire alarm system.

*In a location containing a shower, what is the horizontal limit of zone 1 for showers without a basin?
The limit of zone 1 horizontally is 1.2 m from the centre point of the fixed water outlet (the end of the rigid pipe of the fixed water installation) on the wall or ceiling, irrespective of whether the shower head is fixed or on the end of a flexible hose. Beyond zone 1, the general rules of BS 7671 apply, including Regulation 512.2 concerning external influences. In particular, the IP rating of any electrical equipment must be adequate. 701.32.4 : 512.2 :

Regulation 560.7.7 requires cables for safety circuits, other than metallic screened fire-resistant cables, to be adequately and reliably separated from other circuit cables. In addition to mineral insulated cables, what cables would be exempted from this separation requirement ? (560.7.7 )
Soft-skinned cables to BS 7629-1: 2008 would be exempted from the separation requirements as they have a metallic screen and their survival in a fire has been tested in accordance with BS EN 50200. However, cables to BS 8436: 2004 would not be exempted as the product standard does not require their fire resistance to be tested. Irrespective of the above, BS 5839-1 recommends that, for a fire detection and alarm system complying with that standard, the circuits of fire alarm systems should be segregated from the cables of other circuits to minimize the potential for those other circuits to cause malfunction of the fire alarm system.
* As the designer of an installation, am I allowed to rely on the RCD element of an RCBO to provide for fault protection in order to allow for loop impedance values greater than given in Table 41.3?
Yes, so long as all the other applicable requirements of the 17th Edition are met, including those for protection against overload and short circuit. 411.4.4 : 411.4.5 : 411.4.9 :
* Are there any particular requirements relating to the mounting height or location of consumer units for electrical installations in new dwellings?
The provision of access to consumer units is not specifically covered by Building Regulations or BS 7671. However, consumer units need to be so located as to enable reasonable access to the users, including for the purpose of testing the RCDs at regular intervals, and in case of emergency. 132.12 : 341.1 : 513.1 :
* Is the space within an airing cupboard in a bathroom or shower room that would otherwise be in a particular zone were it not for the cupboard door, considered to be within that zone?
No, unless the cupboard door does not effectively limit the extent of the location. However, where an airing cupboard opens into zone 1 or zone 2, we recommend that circuits supplying equipment in the airing cupboard are be provided with additional protection in accordance with Regulation 415.1.1. 701.32.1 : 701.411.3.3 :
Note: Unless otherwise indicated, all references to ‘RCD’ in this section relate to residual current devices having a rated residual operating current ( I∆n ) not exceeding 30 mA and an operating time not exceeding 40 ms at a residual operating current of 5 ( I∆n ) provided as additional protection in the event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users (Regulation 415.1.1)

PLACES OF WORK – NEW INSTALLATIONS :

The 17th Edition requires socket-outlets rated at up to 20 A and intended for use by ordinary persons to be provided with additional protection by means of a 30 mA RCD. Many socket-outlets in offices may be considered to be subject to this requirement. However, many offices will have computers producing protective conductor current, individually and/or collectively. This accumulated protective conductor current could cause the circuit RCD to operate. Such disruption will not be acceptable to the office users, particularly in banks etc. How can such unwanted tripping be avoided?
Where additional protection by RCD is necessary, unwanted tripping can be avoided by appropriate sub-division of circuits. 314.1, 531.2.4.
*Which 13 A socket-outlets in commercial and industrial premises are required to have additional protection by RCD?
Socket-outlets in commercial and industrial premises must have additional protection by means of an RCD if they are rated at 20 A or less and are for general use without the supervision of a skilled or instructed person. An exception is made for a specific labelled/identified socket-outlet for a particular item of equipment. 411.3.3 :
The decision as to which socket-outlets are provided with RCD protection in accordance with these criteria should be made in consultation with the client’s duty holder under the Electricity at Work Regulations 1989 :
As a general principle, it may be considered that socket-outlets in commercial and industrial premises needing to have additional protection by means of an RCD include the following: those in common, circulation and public areas; those in self-catering areas; those intended for use by cleaners; and those that may reasonably be used to supply mobile equipment for use outdoors.
*Which socket-outlets in commercial and industrial premises are NOT required to have additional protection by RCD?
Socket-outlets in commercial and industrial premises must have additional protection by means of an RCD if they are rated at 20 A or less and are for general use without the supervision of a skilled or instructed person. An exception is made for a specific labelled/identified socket-outlet for a particular item of equipment. 411.3.3 :
The decision as to which socket-outlets are provided with RCD protection in accordance with these criteria should be made in consultation with the client’s duty holder under the Electricity at Work Regulations 1989.
As a general principle, it may be considered that socket-outlets in commercial and industrial premises NOT needing to have additional protection by means of an RCD include the following: a socket-outlet labelled for the connection of a specific item of equipment; socket-outlets not intended for general use, such as those in floor service boxes intended for the connection of workstations and other IT equipment; socket-outlets for use under the supervision of skilled or instructed persons so as to minimize the possibility of careless use.
* If an RCD is used to achieve automatic disconnection within the prescribed time, is the supplementary bonding called for in 411.3.2.6 still required? 411.3.2.2, 411.3.2.3, 411.3.2.4 :
No. An RCD is a valid way of complying with automatic disconnection requirements. 411.4.4 :
* In a milking parlour, is supplementary bonding required only where livestock can make simultaneous contact with extraneous-conductive parts (such as metallic gate posts and gates) and exposed- No. The 17th Edition requires all extraneous- and exposed-conductive-parts that can be touched by livestock to be supplementary bonded, whether or not the parts are simultaneously accessible.
No. The 17th Edition requires all extraneous- and exposed-conductive-parts that can be touched by livestock to be supplementary bonded, whether or not the parts are simultaneously accessible.
* Does a portacabin that is intended to be moved from place to place only infrequently, and which is supplied for example by SWA cable, fall within the scope of Section 717 of the 17th Edition? 717.1
No. Section 717 applies to transportable units that are intended to be moved relatively frequently from place to place and which therefore need to be supplied through flexible cables.

 

[amberleaf]

PERIODIC INSPECTION OF EXISTING DOMESTIC AND SIMILAR INSTALLATIONS :

* During periodic inspections of domestic electrical installations, I often find that cables that are concealed in walls at a depth of less than 50 mm have no additional protection by means of an RCD, as is now required for installations complying with the 17th Edition. What Recommendation Code should I give ?
Code 4. Although existing installations need to be assessed against the requirements of the 17th Edition, this does not necessarily mean that they require upgrading, unless a departure from the latest requirements constitutes an immediate or potential danger. Introduction to BS 7671: 2008

*What Recommendation Code should be given if it is found that there is no supplementary bonding in a bathroom, and the alternative protective measures called for in the 17th Edition are not present ?
Recommendation Code 2
* Is it necessary to verify voltage drop during a periodic inspection?
Verification of voltage drop is not normally required unless there is considered to be a voltage drop problem. 621.2
*What should be recommended if, during a periodic inspection, the safety of an installation forming part of a TT system is found to be relying on a voltage-operated earth-leakage circuit-breaker (VOELCB) for fault protection?
If a VOELCB on a TT system fails to operate when tested with an instrument or integral test button, this would normally warrant a Code 1 recommendation (requires urgent attention).
But, subject to the VOELCB being proved to operate correctly, continued reliance on it for fault protection (protection against indirect contact) would normally warrant a Code 4 recommendation.
However, if the VOELCB relies on a water pipe not permitted by Regulation 542.2.4 to be a means of earthing, this should attract a Code 2 recommendation (requires improvement).

 

[amberleaf]

Periodic Inspection Reporting -
Recommendation Codes for Domestic and Similar
Electrical Installations ,

In General Terms : The Recommendation Codes should be Used as Follows :

Code (1) ( Requires Urgent Attention )
This code is to be used to indicate that danger exists ,
Requiring urgent remedial action .
The persons using the installation are at risk . the person ordering the report should be advised to take action without
Delay to remedy the observed deficiency in the installation , or to take other appropriate action ( such as switching off –
And isolating the affected parts of the installation ) to remove the danger . the inspector should not wait for the full report
To be issued before giving this advice .

As previously indicated . some certification .
Registration and membership bodies make available “ Dangerous Condition “ notification forms to enable inspectors to record ,
And then to communicate immediately to the person ordering the report , any Dangerous condition discovered ,

Code (2) ( Requires Improvement )
This code is used to indicate that the observed deficiency requires action to remove potential danger .

The person ordering the report should be advised that ,
Whilst the safety of those using the installation may not be at immediate risk , remedial action should be taken as soon as possible
To improve the safety of the installation ,

Code (3) ( Requires further investigation )
It would be unusual to need to attribute a Recommendation Code 3 to an observation made during the periodic inspection of a domestic or similar installation ,

However , the code could be used to indicate , that the inspector was unable to come to a conclusion about an aspect of the installation or . alternatively . that the observation was outside the agreed purpose , extent or limitations of the inspection ,
But has come to the inspectors attention during the inspection and testing

The person ordering the report should be advised that the inspection has revealed an apparent deficiency which could not , due
To the agreed extent or limitations of the inspection , be fully indentified , and that the deficiency should be investigated as soon as possible .
A Recommendation Code 3 would usually be associated with an observation on an aspect of the installation that was not foreseen
When the purpose and extent of the inspection , and any limitations upon it , were agreed with the client .

The purpose of periodic inspection is not to carry out a fault-finding exercise .
But to assess and report on the condition of the installation within the agreed extent and limitations of the inspection .

Code 4 ( does not comply with the current issue of BS-7671 )
This code is to be used to indicate that certain items have been identified as not complying with the Requirements of the current issue of BS-7671 , but that the users of the installation are not in any danger as a result ,

The person ordering the report should be advised that the code is not intended to imply that the installation is unsafe , but
That careful consideration should be given to the benefits of improving those aspects of the installation ,

General requirements :

Where you observe a real and immediate danger that puts the safety of those using the installation at risk, you
should give a Recommendation Code 1 (requires urgent attention). You should also advise the customer
immediately (preferably in writing) that urgent work is necessary to remove the danger. This action is
necessary to satisfy the duties imposed on the inspector
and others by the Health and Safety at Work etc Act 1974 and the Electricity at Work Regulations 1989.

A Code 2 recommendation should be given where

the observed deficiency requires action to remove potential danger. In that case the customer should be
advised that, whilst the safety of those using the installation may not be at immediate risk, action should
be taken without delay to remove the potential danger to make the installation safe.

We believe it would not be reasonable to report that the condition of the installation is ‘satisfactory’ if any
observation in the report has been given a Recommendation Code 1 or Code 2 according to Best
Practice Guide No. 4,

The recommended interval until the next inspection should be made conditional upon all the observations
with a Recommendation Code 1 or Code 2 being put right to make the installation safe.
It would be unusual to give a Recommendation Code 3 (requires further investigation) to an observation made
during the periodic inspection of a domestic or similar installation. Where a Code 3 is justified, and there is no
Recommendation Code 1 or 2, you should consider your overall assessment of the condition of the
installation carefully before deciding whether to record it as ‘satisfactory’ or ‘unsatisfactory’ in the report.

Dangers :
During the inspection, you should identify any dangers that might occur during testing, and take appropriate
safety precautions. Where it is necessary to inspect live parts inside equipment the supply to the equipment
must first be isolated, proved dead and locked off, prior to access

Dangerous conditions

If you identify a dangerous condition, you should contact the customer urgently to get permission to
carry out any necessary work to make the condition safe. While waiting for permission, you should make
every effort to reduce the risk of danger to people, animals and property. If necessary the area of danger
should be blocked off and appropriate warning notices fitted.

Disturbance to the installation of the property and its owner (or occupier) :

Any inspection and testing should be done without disturbing the electrical installation or the occupier of
the dwelling more than is necessary. Where it is necessary to disconnect part or all of an installation to
carry out a test, you should do this at time agreed with the owner (or occupier).

Questions :

You may need to ask the homeowner about:
• diagrams of the electrical installation;
• records of previous electrical installation
inspections and tests;
• the electricity supply, for example, the location of
the consumer unit and meter; and
• earthing arrangements, for example, the location
of any protective bonding clamps (such as at the
stopcock for the water main or gas supply).
Usually the homeowner will not have this information,
and you will need to carry out some exploratory work so
inspection and testing can be done safely and
effectively. This work will include gathering information
about circuits, switchgear and controlgear.

Changes :

You should make a note of any known changes, either
in environmental conditions, the structure of the
building or any alterations or additions affecting the
suitability of the present installation, such as whether or
not the method of wiring is still suitable for its present load or environment

Visual inspection of electrical equipment :

You should make a thorough visual inspection of all electrical equipment that is not concealed, including
the accessible internal condition of an appropriate sample of all equipment. (Normally, for each circuit, a
sample of at least 20% to 30% of the accessories or points is necessary.)
The condition of the equipment and of any damage found should be noted and recorded in the report. The
condition of all electrical equipment and materials

sample of at least 20% to 30% of the accessories or points is necessary.)
The condition of the equipment and of any damage found should be noted and recorded in the report. The
condition of all electrical equipment and materials
should also be noted, taking into account any information from the manufacturer. The notes should cover:

• safety
• wear and tear
• corrosion
• damage; excessive loading (overloading)
• age
• external influences (such as mechanical impact or presence of water), and
• if the equipment is suitable for the installation.

You should assess condition of the equipment, together with any changes made to the building or its services
which affect electrical safety.

• Switchgear.
• Luminaries.
• Socket-outlets.
• Other electrical points (such as lighting and cooker points).

Any sign of overheating, overloading or damage to the insulation, armour, sheath or conductors needs to be noted.

Flexible cables and cords :

Where a flexible cable or cord forms part of the fixed wiring installation, your inspection should include:
• an examination of the cable or cord, for damage or faults

• an examination of the terminations and anchorages for damage or faults, and
• evidence of correct installation and extra
protection against mechanical damage and heat,
for example, by using heat-resistant sleeving.
Accessories and switchgear You should make a thorough internal visual inspection
of the accessible parts of a sample of accessories and switchgear to assess their electrical and mechanical condition.
However, every switching device that is a part of the installation under inspection will need to be inspected if the sample inspection shows up:
• results that are noticeably different from any results recorded previously
• results that are noticeably different from those expected, or
• poor conditions (for example, fluid in the accessories or switchgear, or worn or damaged
mechanisms), unless there is clear evidence of how the damage to the equipment occurred.

Protective devices :

You should confirm that protective devices, such as circuit-breakers, fuses and RCDs are:
1. in the correct position
2. in good working order
3. suitable for the type of earthing system
4. of the correct type, size and overload rating (or setting) for the circuits that they protect
5. easy to access for normal operation, maintenance and inspection, and
6. labelled correctly.

 

[amberleaf]

Ring Circuit :

R1 = 0.42Ω Line / Line : Ring Final Circuits ( Measured End to End ) Continuity ( Dead Test )
Rn = 0.43Ω Neutral / Neutral : Ring Final Circuits ( Measured End to End ) Continuity ( Dead Test )
R2 = 0.73Ω Earth – Earth : Conductor : Ring Final Circuits ( Measured End to End ) Continuity ( Dead Test )

Leads on Line Conductor / Neutral Conductor

* Ring – Circuit : Line and Neutral ↔ Line and Neutral : on Connector Block R1 / Rn ( Set on Ohms : Tested 0.19Ω )
* Ring – Circuit : Line and Neutral at each Sockets , Adapter Socket for Leads = 0.20
Spur on the Ring / will be higher : Ω

Leads on Line Conductor / Earth Conductor

* Ring – Circuit : Line and Earth ↔ Line and Earth : on Connector Block at CCU : = 0.23Ω
* Ring – Circuit : Line and Earth : → Adapter Socket for Leads = 0.25Ω .. at each Socket in Ring ,

R1 + R2 All circuits ( At Least one Column to be Completed )
0.43 + 0.73 = 1.16 ( 1.16 ÷ 4 = 0.29Ω )
1.16 ÷ ( 4 ) = 0.29Ω ( along as the Reading was Not taking with a Spur on the Ring ( 4 ) ←

Remember to Null leads : or subtract :

( Big Copper Lower Résistance )

 

[amberleaf]

Lighting Circuits , ( Dead Test ) Lighting Circuit is a Parallel Circuit :

Line / Earth : on Connector Block at CCU :
At Pendent : Lead on CPC / Lead on Switch Live , = 0.70Ω
Switch is On at testing
( Polarity can be Checked by turning the switch OFF ) “ Open Circuit “ > 9999 or 2000 ≈ 0º / 180º ≈ Testing ,

The furthest Light ( R1 + R2 )

Remember to Null leads : or subtract :

Code 3 ( Requires further investigation )
Observations’ that would usually warrant a Code 3 :

Recommendation include :

* Unable to trace final circuits :
* Unable to access equipment or connections needing to be inspected that are known to exist but have been boxed in such as by panels or boards that cannot be easily removed without causing damage to decorations :
* insulation résistance of less than 1 Megohms between Live conductors connected together and Earth ,
When measured at the consumer unit with all final circuit connected ,

Domestic Inspection & Testing : 2392-10

External Earth Fault Loop Impedance “ Ze “ : ( Danger Live Test )

Main Eathing Conductor Disconnected 16mm2 ( Parallel Paths )

RCD Non – Trip Tester : ( 3 – Leads )

Locked OFF : ( Caution : Electrician at work do not switch on )

Lead on Earth , 1st ← 16mm2
Lead on Neutral , 2nd ← ←← : this may come up :
Lead on Line , Testing : 241V ( Polarity Checked ) = 0.69Ω 1st ← “ Good Practice to Repeat this Test “( 0.66Ω ) 2nd

Highest off the Two Readings : ←

Re-Connect Main Eathing Conductor 16mm2 :

External Earth Fault Loop Impedance “ Ze “ Commonly used for ( Ra ) for TT Systems :

Measurement of Installation Earth Electrode Résistance

* Method (1) fusing a four-terminal Proprietary Earth Electrode Test Instrument :
20 ↔ 30 m ↔ : 2m ← → 2m
Method (1) fusing a three-terminal Proprietary Earth Electrode Test Instrument :
20 ↔ 30 m ↔ : 2m ← → 2m
Temporary Test Rods

Domestic CCU : 2392-10

416.2.2 : IP4X : hole no greater than 1mm ( Top )

416.2.4 : IP2X : hole no greater than 12.5mm ( Sides & Fronts )
No deeper than 80mm into the Enclosure

Segregation of Band I & Band II circuits or Band II insulation used :

Band II ( Normally low voltage ) 50 volts :
Band I (Normally Extra-low voltage ) 120 volts :
Band I / Band II - can only be contain in the same Wiring Systems : ( 528.1 ) if Adopted ;

Domestic Inspection & Testing :

Measurement of Maximum Prospective Fault Current , ( Danger Live Test )
This is Locked OFF :
Prospective Earth Fault Current :

Lead on Main Eathing Bar 1ST
Lead on Neutral 2nd
Lead on Live

Tester : 242 V loop Reading = 0.66Ω this will very though out the day
You have parallel paths in ( PFC ) 375 A

Next Test :
Prospective Short Circuit Current :
With 3 – Leads : you put Green one onto the Blue one
Line by its self
Short is Between ( Live & Neutral )

Lead on Neutral 1st
Lead on Line 2nd
Good Practice to Repeat this Test “

Expecting a Low Loop Reading here , lot more Copper in Circuit , = 0.53Ω
242 V ( PFC 458 Amp )

Highest Reading on to the Test / Schedule of Test Results , kA ( PFC )
Prospective Fault Current :
At Consumer Unit(s) kA

Amps to kA

Reading , 760A ÷ 1000 = 0.76kA
Reading , 1760A ÷ 1000 = 1.76kA

Domestic Inspection & Testing :

Earth Fault Loop Impedance ( Zs ) by Measurement and by Calculation : ( Danger Live Test )

Cover been put on the Consumer Unit and Supply Connected

This Live Test should only be taken on Sockets , they have No exposed parts
243 v ( Polarity Correct ) 1st Loop = 0.72Ω Around all Sockets : 2nd Loop = 0.74Ω / 234V

The Highest Reading you obtain : / Schedule of Test Results , ↔
Maximum Measured Earth Fault Loop Impedance , Zs Ω

RCD no-Trip Tester ,

Calculation to Determine
Earth Fault Loop Impedance ( Zs )
Zs = Ze + R1 + R2 )
Zs = Ze + 0.8
Zs = 0.69 + 0.8 = Zs = 1.49Ω

Zs = 1.49Ω
Radial Circuit ,

Domestic Inspection & Testing :

Polarity Tests :
Confirmed on other ways , ( R1 + R2 ) ( Ze ) ( Zs ) Confirmed Polarity ,

Metal Trunking :

(1) Line and Natural cables contained in the same metal trunking ( 521.5.2 )
(2) Protected against damp or corrosion ( 522.3 & 522.5 )
(3) Earthed ( 411.4.2 )
(4) Joints mechanically sound and of adequate continuity ( 543.2.4 )

Busbar Trunking and powertrack systems :

(1) Busbar Trunking to comply with BS-EN 60439-2 or other appropriate standard and powertrack system to comply with
BS-EN 61534 series or other appropriate standard ( 521.4 )
(2) Securely fixed and adequately protected against mechanical damage ( 522.8 )
(3) Joints mechanically sound and of adequate continuity ( 543.2.4 )

Conduits :

(1) Securely fixed, box lids in place and adequately protected against mechanical damage ( 522.8 )
(2) Inspection fittings accessible ( 522.8.6 )
(3) Number of cables for easy draw not exceeded 9 522.8.1 & See , On Site Guide Appx 5 )
(4) Solid elbows and tees used only as permitted ( 522.8.1 & 522.8.3 )
(5) Ends of conduit reamed and bushed ( 522.8 )
(6) Adequate boxes suitably spaced ( 522.8 and see , On Site Guide Appx 5 )
(7) Unused entries blanked off where necessary ( 412.2.2 )
(8) Conduit system components comply with a relevant British Standard ( Section 511 )
(9) Provided with drainage holes and gaskets as necessary ( 522.3 )
(10) Radius of bends such that cables are not damaged ( 522.8.3 )
(11) Joints , scratches , etc. in metal conduit protected by painting ( 134.1.1 & 522.5 )

Rigid Metal Conduit :

(1) Complies with BS-EN 50086 or BS-EN 61386 ( Section 511 )
(2) Connected to the main earth terminal ( 411.4.2 )
(3) Line and Neutral cables contained in the same conduit ( 521.5.2 )
(4) Conduit suitable for damp and corrosive situations ( 522.3 & 522.5 )
(5) Maximum span between buildings without intermediate support ( 522.8 and see Guidance Note 1 and On Site Guide Appx 5 )
Guidance Note 1 ↔ “ Selection and Erection of Equipment “

Rigid Non-Metal Conduit :

(1) Complies with BS-4607 , BS-EN 60423 . BS-EN 50086-2-1 or the BS-EN61386 . series ( 521.6 )
(2) Ambient and working temperatures within permitted limits ( 522.1 and 522.2 )
(3) Provision for expansion and contraction ( 522.8 )
(4) Boxes and fixings suitable for mass of luminaire suspended at expected temperature ( 522.8 , 559.6.1.5 )
Greggs : ( 559.6.1.4 ) ( LSC )

Flexible Metal Conduit :

(1) Complies with BS-EN 60423 & BS-EN 50086-1 or the BS-EN 61386 series ( 521.6 )
(2) Separate protective conductor provided ( 543.2.1 )
(3) Adequately supported and terminated ( 522.8 )

Trunking :

General ,
(1) Complies with BS-4678 or BS-EN 50085-1 ( 521.6 )
(2) Securely fixed and adequately protected against mechanical damage ( 522.8 )
(3) Selected , erected and routed so that no damage is caused by ingress of water ( 522.3 )
(4) Proximity to non-electrical services ( 528.2 )
(5) Internal sealing provided where necessary ( 527.2.4 )
(6) Holes surrounding trunking made good 9 527.2.1 )
(7) Band I circuits partitioned from Band II circuits or insulated for the highest voltage present ( 528.1 )
(8) Circuit partitioned from Band I circuits or wired in mineral-insulated metal-sheathed cables ( 528.1 )
(9) Common outlets for Band I and Band II provided with screens , barriers or partitions ,
(10) Cables supported for vertical runs ( 522.8 )

Areas common to most buildings ( Lux ) Lighting :

Entrance hall , Lobby , Waiting room 200 Lux
Enquiry desk 500 Lux
Corridor , Passageway , Stairs 100 Lux
Atria 50 – 200 Lux
Changing room , Cloakroom , Lavatory 100 Lux
Rest room 150 Lux
Canteen , Cafeteria , Dining room 200 Lux
Kitchen 300 Lux

Offices :

General Offices 500 Lux
Computer Workstations 300 – 500 Lux
Conference room , Executive Office 300 – 500 Lux

Banks & Building Societies :

Counter , Office Area : 500 Lux :
Public Area : 300 Lux :

Retailing :

Fashion : 500 / 750 Lux
Supermarket 750 : Lux
Restaurant 200 Lux
Bookshop , Chemist , Jeweller 500 Lux
Superstore 1000 Lux
Electrical / Furniture Store 750 Lux
Showroom 500 / 750 Lux
Arcades and Malls 50 / 300 Lux

Places of Public Assembly :

Cinema and Theatre Foyer 200 Lux
Booking Office 300 Lux
Auditoria 100 – 150 Lux
Library 150 – 300 Lux
Museum Art Gallery 50 – 300 Lux
Lecture Theatre 300 Lux
Church 100 – 300 Lux

Hotels :

Entrance Hall 100 Lux
Reception on Desk 300 Lux
Bar , Restaurant , Dining room , Lounge 50 – 200 Lux
Bedroom 50 – 100 Lux
Kitchen 150 – 300 Lux

Areas Common to Most Buildings

Performing a Test on SWA :

length of SWA 2.5mm 3 core wired into a Consumer Unit at one end and an isolator at the other.
how to perform a test on SWA ;

1 , Continuity ( 612.2

2 , Insulation Resistance ( 612.3

3 , Polarity ( 612.6

Performing a Test on SWA :

Isolate Consumer Unit :

( 1 ) Remove conductors from CU , terminals

( 2 ) Connect line to cpc of SWA & test continuity at the load side of isolator between line & cpc, turn isolator on / off
while testing proves line is switched ( R1 + R2 done & polarity )

( 3 ) Remove link between line & cpc

( 4 ) Set meter to 500v test IR between line & cpc

( 5 ) Test IR between line & neutral

( 6 ) Test IR between neutral & cpc

 

[amberleaf]

Motor Circuits :

Loop impedance tests on motor circuits can only be carried out on the supply side of isolated motor controlgear .
Continuity tests between the circuit protective conductor and motor are then necessary ,

Circuits incorporating an RCD :

Where the installation incorporates an RCD , the value of earth fault loop impedance obtained in the test should be related to
The rated residual operating current ( I∆n ) of the protective device , to verify compliance with Section 413 of BS-7671 ,

Zs ( I∆n ) ≤ 50 for TN-Systems :

411.5.3 : Ra ( I∆n ) ≤ 50 for TT-Systems :

Operation of residual current devices :
612.8.1 Where there is RCD protection , the effective operation of each RCD must be verified by a test simulating an appropriate fault condition independent of any test facility ( 411.3.3 ) incorporated in the device ,
Followed by operation of the integral test device , the nominal rated tripping current should not exceed 30mA where the
RCD provides additional protection for socket-outlets not exceeding 20A intended for general use by ordinary persons or mobile equipment having a current value not exceeding 32A that is being used outdoors ,

Inspection Checklist :

( This checklist may also be used when carrying out periodic inspections )

General ,

(1) Complies with requirements : ( 133.1 – 134.1 )
(2) Accessible for operation , inspection and maintenance ( 513.1 )
(3) Suitable for local atmosphere and ambient temperature ( Ch 52 ) see BS-EN 60079 for electrical apparatus for the use in an explosive gas atmosphere and BS-EN 61241 for electrical apparatus for use in the presence of combustible dust )
(4) Circuits to be separate ( No borrowed Neutrals 314.4 )
(5) Circuits to be identified ( Neutral and Protective conductors in the same sequence as Line conductors 514.1.2 – 514.8.1 )
(6) Protective devices adequate for intended purpose ( Ch 53 )
(7) Disconnection times likely to be met by installed protective devices ( Ch 41 )
(8) Sufficient numbers of conveniently accessible socket-outlets are provided in accordance with the design ( 553.1.7 )
(9) All circuits suitably identified ( 514.1 – 514.8 -514.9 )
(10) Suitable main switch provided ( Ch 53 )
(11) Supplies to any safety services suitably installed , e.g. Fire Alarms to BS 5839 and Emergency lighting to BS 5266
(12) Environmental IP requirements accounted for ( BS-EN 60529 )
(13) Means of isolation suitably labelled ( 514.1 – 537.2.2.6 )
(14) Provision for disconnecting the Neutral ( 537.2.1.7 )
(15) Main switches to single-phase installations , intended for use by an ordinary person , e.g. domestic . shop . office premises . to be double-pole ( 537.1.4 )
(16) RCDs provided where required ( 411.1 – 411.3 -411.4 - 411.5 – 522.6.7 – 522.6.8 – 532.1 -701.411.3.3 – 701.415.2 – 702.55.4 – 705.411.1 – 705.422.7 – 708.553.1.13 – 709.531.2 – 711.410.3.4 – 711.411.3.3 - 740.410.3 - 753.415.1 )
(17) Discrimination between RCDs considered ( 314 – 531.2.9 )
(18) Main earthing terminal provided ( 542.4.1 ) readily accessible and identified ( 514.13.1 )
(19) Provision for disconnecting earthing conductor ( 542.4.2 )
(20) Correct cable glands and gland plates used ( BS-6121 )
(21) Cables used comply with British or Harmonised Standards ( appendix 4 of the Regulations 521.1 )
(22) Conductors correctly identified ( section 514 )
(23) Earth tail pots installed where required on mineral insulated cables ( 134.1.4 )
(24) Non conductive finishes on enclosures removed to ensure good electrical connection and if necessary made good after connecting ( 526.1 )
(25) Adequately rated distribution boards ( BS-EN 60439 may require derating )
(26) Correct fuses or circuit-breakers installed ( Sections 531 & 533 )
(27) All connections secure ( 134.1.1 )
(28) Consideration paid to electromagnetic effects and electromechanical stresses ( Ch 52 )
(29) Overcurrent protection provided where applicable ( Ch 43 )
(30) Suitable segregation of circuits ( Section 528 )
(31) Retest notice provided ( 514.12.1 )
(32) Sealing of the wiring system including fire barriers ( 527.2 )

There are Two Methods for Measuring the values of ( PFC ) but these can only be used when the supply has already been connected .
By then , the fuses and circuit breakers will already be installed .

The first Method is to Measure the Impedance of the supply by Determining its Voltage Regulation ,
That is the amount by which the Voltage falls with an increase in current ,
For Example : Consider an Installation with a no-load terminal voltage of 230V . if when a current of 40A flows ,
The voltage falls to 228V . the volt drop will be due to the Impedance of the Supply ,

Thus ( Zs ) = Systems volt drop = 230 – 228 Ω = 2 Ω
……………. Current ………………......... 40 ……….. 40 …………… 2Ω ÷ 40A = 0.05 Ω


Then ( PFC ) = Uo = 230V = 4600A / or 4.6 kA
……………………..... Zs …….. 0.05Ω …… ( 230V ÷ 0.05Ω = 4600 kA - ( PFC )


A Second Measurement Method is to use a Loop Impedance Tester , and Connected to Phase – Neutral
( Instead of Phase and Earth ) to Measure Supply Impedance , This can then be used with the Supply voltage as above to Calculate ( PFC ) ,

Some Manufacturers modify their Earth-loop testers so that this connection is made by selecting “ PFC “ with a switch .
The instrument measures supply voltage , and Calculate . then displays ( PFC )

A possible difficulty in measuring ( PFC ) and thus being able to use fuses or circuit breakers with a lower breaking capacity
Than that suggested by the supply Company , is that the supply may be reinforced . more load may result in extra or
Different transformers’ and cables being installed , which may reduce supply Impedance an Increase ( PFC )

Using 240V - 238 = 2Ω ( 2 ÷ 40A = 0.05Ω ) 240 ÷ 0.05Ω = 4800 kA ( PFC )

Extent of the Work :

When entering into an agreement for the Periodic Inspection and Testing of a building under your control it is a fundamental requirement that the extent and limitations of the inspection and testing be fully described for the contractor. It is recommended that the following procedures are adopted and that the relevant points be discussed with the contractor prior to completing the agreement documents.
* Determine your requirements for inspection and testing and tailor the procedures accordingly.

* Agree before commencing the work the amount of down time that can be tolerated and arrange a provisional programme for switching off:

- Totally.
- Individual Areas or Distribution Boards.
* It is important that these times are confirmed immediately prior to the contractor switching off.

* As it is neither practical nor possible to inspect all parts of the installation, a sampling process will be employed, normally in the order of 10% of all accessories, lighting fittings and control equipment.

* Detail any limitations of the inspection and testing to be carried out and explain that the installation must not be dismantled in any way other than opening equipment covers, and that the building structure must not be disturbed. This means that concealed cables and equipment will not be inspected.

* Identify any new parts of the installation that may not need to be included in the work.

Contractor's Reports :
On completion of the Inspection a report should be provided by the contractor, detailing, to the best of their knowledge and belief, the condition of the installation, results of all tests carried out, a list of recommendations and a conclusion as to whether the installation is safe to use in its present state. If the conclusion drawn is that the installation is unsafe, then the supply should be switched off and notices placed warning of the danger before the contractor leaves site.
Visual Inspection Only :
Check for any obvious mechanical damage or deterioration of materials and equipment, exposed cables and live parts, missing covers, fixings, labels and notices etc.
N.B. This procedure will not necessitate switching off the installation.
Visual Inspection Supplemented By Testing
Visual Inspection :
Repeat as for Visual Inspection Only but also include a thorough inspection of:
* The main switchgear and all distribution boards. These should be inspected for the following:
• Fuses and MCBs are correctly rated for over-current and fault current
• Fuse and switch contacts are clean and have not been over-heating
• Conductor terminations are tight and correctly lugged (if possible)
• Busbar connections are properly made and clamps are tight.

* Cables - whenever possible cables should be inspected to ascertain:
• The suitability for the load and operating environment
• The condition of the insulation and protection
• Adequacy of fixings and mechanical protection
• Suitability of glands and shrouds
• Proper use of earthing rings and earth connections
• Any signs of over-heating and damage.

* Equipment, accessories and lighting fittings should be inspected for:
• Deterioration due to the atmosphere, mechanical damage, over-heating and adequate fixings.
• Connections of conductors and condition of flexes.
This should include removing light fitting covers, switch plates, socket outlets and covers of equipment.
A sample of approximately 10% of all parts and areas of the installation should be inspected.
N.B. Actual % to be agreed with yourselves.

 

[amberleaf]

BS-7671:2008 Part 2 - page 32 fig- 2.1 ↔ (2) ( Old Equipotential bonding ) ↔ Main Protective Bonding Conductor 10mm2 → (2)

R2 – or Wander Lead Method :

50 meters : Wander Lead has a Résistance of One Ohm
Check this with the other Lead ( Testing Two Leads together )
On the Continuity Setting : Giving a reading off - R: 1.13Ω
(1) Null out or (2) Subtract at end off testing

( R2 ) When Testing Main Protective Bonding Conductor , it must be Disconnected both Ends :
Connect one Lead to Main Protective Bonding Conductor at ( CCU )
Connect one Lead to Main Protective Bonding Conductor at ( Main Water Pipe )
On the Continuity Setting : Giving a reading off - R : 0.03Ω
At this stage you have Continuity ,

On-Site Guide BS-7671 :2008 ( Table 9A )

Résistance of 10mm2 Copper Conductor ( 10 – 1 meter length - 1.83 MΩ ←

100 metres = 0.18Ω s approx ,
10 metres = 0.02Ω s approx ,

0.03Ω s = 15 metres approx ,

This Test is repeated the same way for the Gas : Main Protective Bonding Conductor 10mm2 and the Earthing Conductor

If the Main Protective Bonding Conductors & the Earthing Conductors , if they are visible through out is Length it is not necessary to do Continuity ( R2 )

 

[amberleaf]

Periodic Inspection Report :
Guidance for Recipients ( to be appended to the Report )

This periodic Inspection Report form is intended for reporting on the condition of an existing electrical installation ,

You should have received an original Report and the Contractor should have retained a duplicate .
If you were the person ordering this Report , but not the owner of the installation , you should pass this Report , or a copy of it , immediately to the owner ,

The original Report is to be retained in a safe place and be shown to any person inspecting or undertaking work on the
Electrical installation in the future , if you later vacate the property , this report will provide the new owner with details of the condition of the electrical installation at the time the report was issued ,

The ” Extent and Limitations “ box should fully identify the extent of the installation covered by this report and any limitations on the inspection and tests , the contractor should have agreed these aspects with you and with any other interested parties ( Licensing Authority , Insurance Company , Building Society etc ) before the inspection was carried out .

The report should identify any departures from the safety requirements of the current Regulations and any defects , damage or
Deterioration that affect the safety of the installation for continued use , FOR ITEMS CLASSIFIED AS “ REQUIRES URGENT ATTENTION “ THE SAFETY OF THOSE USING THE INSTALLATION MAY BE AT RISK ,
And it is recommended that a competent person undertakes the necessary remedial work without delay .

For safety reasons , the electrical installation will need to be re-inspected at appropriate intervals by a competent person . the maximum time interval recommended before the next inspection is stated in the Report under “ next Inspection “

The Report is only valid if a Schedule of inspections and a Schedule of Test Results are appended ,

MINOR ELECTRICAL INSTALLATION WORKS CERTIFICATE :

Guidance for Recipients ( to be appended to the Certificate )

This safety Certificate has been issued to confirm that the electrical installation work to which it relates has been designed , constructed , inspected and tested in accordance with British Standard 7671 ( IEE Wiring Regulations )

You should have received an original Certificate and the contractor should have retained a duplicate Certificate .
If you were the person ordering the work , but not the owner of the installation .
You should pass this Certificate , or a full copy of it , immediately to the owner .

A separate Certificate should have been received for each existing circuit on which minor works have been carried out , this
Certificate is not appropriate if you requested the contractor to undertake more extensive installation work , for which you should have received an Electrical installation Certificate

The “ Original Certificate should be retained in a safe place and be shown to any person inspecting or undertaking further work on the Electrical installation in the future , if you later vacate the property , this Certificate will demonstrate to the new owner that the minor Electrical installation work carried out complied with the requirements of British Standard 7671 at the time the
Certificate was issued ,

Dual Supply : ( 514.15.1 )

When an installation includes a generating set that can be employed as an alternative source of supply in parallel with another source , a label having the wording shown below should be fixed at or near :

(1) the origin of the installation :
(2) the meter position , if remote from the origin :
(3) the consumer unit or distribution board to which the generating set is connected :
(4) all points of isolation of both sources of supply :

WARNING

Isolate both mains and on-site generation before carrying out work :
Isolate the mains supply at …………………………………………..
Isolate the generator at ………………………………………………

External Influences :
( 611.2 ) any known changes in external influences , building structure , and alterations or additions which may have affected
The suitability of the wiring for its present load and method of installation should be noted ,

Note : should also be made of any alterations or additions of an irregular nature to the installation , if unsuitable material has been used , this Report should indicate this together with reference to any evident faulty workmanship or design ,

 

[amberleaf]

Caravan Installations : Part 7 , Special Installations or Locations

( 721.514.1 )
All Caravans and Motor Caravans should have a Notice fixed Near the Main Switch Given Instructions on the Connection and Disconnection of the Caravan Installation to the Electricity Supply

The Notice should be of a Durable Material Permanently fixed , and bearing in Indelible and easily Legible Characters the text shown in BS-7671 Regs : p-211 / fig 721 :

The Inlet shall be Installed :

(i) Not more than 1.8m above Ground Level ,
(ii ) In a Readily Accessible Position ,
(iii) In an Enclosure with a Suitable Cover on the Outside of the Caravan ,

721.537.2.1.1.1

A notice of Durable Material shall be Permanently fixed near the Main Isolating Switch inside the Caravan .
Bearing the Text shown in 721 in the Appropriate Language(s) in Indelible and Easily Legible Characters :

" Remember " any Alterations on Caravans look at this Page Regs : 213

Main Equipotential bonding ( 6mm2 ) ← required from the Main Earthing Terminal to Structural Metallic Parts such as Chassis . which will be Accessible from within the Caravan .

Notes to Table 3.3 / GN-3 * ( 1)
Test : ………………………………… Recommendation :

Protective …………………………….. Between the Earth Terminal of Distribution boards to the following
Conductors …………………………… Exposed-Conductive-Parts :
Continuity ………………………….. * Socket-Outlet Earth Connections ( note 4 )

Bonding …………………………….. * all Protective Bonding Conductors
Conductors ………………………… * all Necessary Supplementary Bonding Conductors
Continuity

Ring Circuit ………………………… where there are proper Records of Previous tests , this test may not be Necessary .
Continuity ………………………….. this test should be carried out where Inspection / Documentation indicate that there may
……………………………………… have been changes made to the Ring Final Circuit

Insulation …………………………… if Tests are to be made :
Résistance …………………………… * between Live Conductors, with Line(s) and Natural Connected
……………………………………….. together, and Earth at all final Distribution boards
…………………………………….. * at Main and Sub-Main Distribution panels, with Final Circuit Distribution boards
Isolated from mains ( note 6 )

Polarity ……………………………. At the following positions :
……………………………………... * Origin of the Installation
……………………………………... * Distribution Boards
……………………………………... * Accessible Socket-Outlets
……………………………………... * Extremity of Radial Circuits ( note 7 )

Earth Electrode ……………… Test each Earth Rod or group of Rods Separately, with the Test links Removed
Résistance ……………… and with the Installation Isolated from the Supply Source .

Earth Fault Loop …………….. At the following Positions :
Impedance …………………… * Origin of the Installation
……………………………….. * Distribution Boards
……………………………….. * Accessible Socket-Outlets
……………………………….. * Extremity of Radial Circuits ( note 8 )

Functional Tests
RCDs ……………………….. Tests as required by Regulation ( 612.13.1 ) followed by Operation of the Functional test button ,

Circuit-Breakers, ……………. Manual Operation to prove that the device(s) Disconnect the Supply .
Isolators and

Notes to Table 3.3 / GN-3 * ( 2 )

(1) The person carrying out the testing is required to decide which of the above tests are appropriate by using their experience and knowledge of the installation being inspected and tested and by consulting any available records :
(2) Where sampling is applied , the percentage used is at the discretion of the tester . however a percentage of less than 10 per cent is inadvisable
(3) The tests need not be carried out in the order shown in the table .
(4) The earth fault loop impedance test may be used to confirm the continuity of protective conductors at socket-outlets and at accessible exposed-conductive-parts of current-using equipment and accessories .
(5) Generally , accessibility may be considered to be within 3 m from the floor or from where a person can stand .
(6) Where the circuit includes surge protective devices ( SPDs ) or other electronic devices which require a connection to earth for functional purposes , these devices will require disconnecting to avid influencing the test result and to avoid damaging them .
(7) Where there are proper records of previous tests , this test may not be necessary .
(8) Some earth fault loop impedance testers may trip RCDs in the circuit .

Earth Fault Impedance : GN-3

Where protective measures are used which require a knowledge of earth fault loop impedance , the relevant impedance should be measured , or determined by an equally effective method .

Earth Fault Loop Impedance tests should be carried out at the locations indicated below :

(1) Origin of the Installation
(2) Distribution Boards
(3) Accessible Socket-Outlets
(4) Extremity of Radial Circuits

Domestic : 2392-10 ( 100A BS-1361 Type II / Max 50A MCB : Max ( 16ooo. kA ) to BS-7671

Continuity of Protective Conductors :

This test is of great importance and arguably the most important of them all for many reasons , despite of this fact at times shortcuts are taken and things are over looked .

Many electrical contractors who carry out testing very rarely understand the reasons for doing such a test , and the acceptable results obtained .

In this section we will not only be showing you how to conduct the test but the reasons for doing it ,
And which method to choose for a particular installation / wiring system .

This is the first test to be conducted in the sequence of tests , the reason for doing it as the first test in the sequence is because of the possible rise in potential across different metallic items that could arise if the CPCs and bonding were not in place or disconnected when carrying out other tests . An example of this is when doing an insulation résistance test , this
Typically puts 500v dc through the system , if metallic items were not bonded , then it could rise to a dangerous voltage .

The Test :
Before we talk about the individual tests . there has been a lot of confusion around the little things that need doing prior to even picking up an instrument .

This test is only conducted on radial circuits ,
( Q ) “ do we or don’t we disconnect the main bonding conductors’ from the ( MET ) ?

(A) “ Well this dependent upon whether the installation is already connected to the supply . if it is an initial verification ( new installation ) then it is permissible to disconnect the protective and → ∫ Equipotential conductors OLD ∫ ←
We are now on the 17th Edition : Main Protective Bonding Conductors from the main earthing terminal to carry out this test ,

If the installation is an existing one ( periodic ) then testing , the protective and Main Protective Bonding Conductors
Must “ NOT “ be disconnected . if this is the case then a loop test may be conducted to verify the integrity of the system .

There are 3 different methods’ that can be used to carry out this test , and is dependent upon a number of factors ,
Ω is the protective conductor under test part of the final circuit or a sub-circuit ?
Ω is the protective conductor under test a bonding conductor ?
Ω does the circuit under test form part of a metallic wiring system ?

Test Method 1 :

Test method 1 uses the phase as a return lead , otherwise known as the ( R1 + R2 ) Method .
This is the most common Method used for final circuits . as in most final circuits , the phase conductor
Runs alongside a CPC conductor and this factor is utilised in the test .
“ Instrument to be used “
“ Low-Résistance-Ohmmeter “
“ Scale to be used “ Ohms Ωs
The low Résistance Ohmmeter is then connected at the most furthest point of the circuit , and a reading is obtained .
This reading is made up of the Résistance of the ( R1 ) Phase Conductor and the ( R2 ) Protective Conductor and is given the name ( R1 + R2 ) .

GN-3 Colum for Recording ( R1 + R2 ) on the Schedule of Test Results .

Method :
Before the test can begin . if the circuit to be tested is not isolated then follow the correct safe isolation procedures .
Step 1 :
A temporary link is made at the distribution board between the Phase & Protective Conductor Systems .
Important :
Null the leads . this is very important as the wander lead will add a considerable résistance to the instrument reading .
If your instrument does not have a null function . then simply subtract the résistance from the actual reading .

(Q) “ but I only want the résistance of the CPC , why am I bothering with the résistance of the Phase ?
(A) “ This method has many advantages , not only to this test , but to other future tests . the main one being we can use Phase Conductor as part of the circuit as it eliminates any awkward and possibly dangerous wander leads draping everywhere . also this ( R1 + R2 ) reading can be used for working out our Earth Fault Loop Impedance Value if we decided not to Measure it ,
Polarity of the circuit is also obtained at the same time , “

Important :
Don’t forget to remove the Link once the test is finished !!!!!!

 

[amberleaf]

Test Method 3 :

Test Method 3 is used where a Metallic Enclosure forms all or part of the Protective Conductor .

It is highly possible that the Protective Conductor under Test forms part of a steel conduit trunking or similar .
If this is the case then a few problems arise . due to possible corrosion or loose joints . the protective conductor résistance
Could rise to unsafe levels .

Parallel paths will form if there is a separate CPC , this must also be taken into consideration .

Because of this there are 3 tests that can be carried out . Only one need be adopted , but they differ due to the difficulty of gaining an accurate reading and increasing severity with regard to current carrying capacity .
1.5 times the design current , with a maximum of 25A to be used . the résistance of the protective conductor can be calculated from ( R2 = V- A )
The résistance between any extraneous conductive part and the main earthing terminal should be 0.05Ω or less ;
We are now on the 17th Edition : ( OLD ) supplementary bonding ,
All Supplementary Protective Bonding Conductors if required should also have the same résistance .

The 3 Tests :
(1) A standard Ohmmeter test as indicated in method 1 or method 2 / R2 ) this will not exploit any high résistance joints in the enclosure , and if used after must be visually expected along the length of run
(2) Phase-Earth loop Impedance test can be carried out if it is thought by the inspector that the soundness of the system is questionable.
(3) if the protective conductor is suspect then a high current test can be used of around

The Maths Involved in the Test .
When doing an inspection and testing course it is highly likely that you will encounter some form of maths involved while
Learning about the tests . at the end of the day electricity is a form of physics which deals with Resistances Voltages & Currents .
The duty holder whom carries out the duty holder whom carries out the inspection & testing must have a knowledge of why he/she is doing it , what to expect of the readings from the instrument and how to interpret these readings

(Q) “ When conducting a Continuity of Protective Conductor test. What kind of calculations could we be asked ?

(1) The value of R2 can be found using method 1 above :
(2) The max length & actual length of the circuit under test can be found when applying method 1 & 2 above .
(3) Subtraction of the wander lead résistance form the reading in method 2 .

2392-10 Fundamental Inspection , Testing & Initial Verification
Q(1) Electrical Test probes must comply with standards set by ?
A(1) a – BS-7671 b – GN-3 c – Guidance Note GS-38 d – BS-EN 60598

Q(2) Which of the following statement is false . during Initial Verification Inspection shall be made to verify ?
A(2) a – equipment has a British Standard or other mark or certification furnished by the manufacturer .
A(2) b – equipment is correctly selected and erected .
A(2) c - equipment is not visibly damaged . A(2) d - equipment is functioning .

Q(3) The person carrying out Inspection and Testing must have ?
A(3) a – an inspection & test qualification . b – sound knowledge and experience relevant to the installation being inspected
A(3) c – both ( a ) and (b) d – a current wiring regulations qualification .

Q(4) Put the following tests in the correct sequence : 1-Phase Sequence 2-Insulation Résistance of non-conducting floors & walls 3-Earth Electrode Résistance 4-Protection by barriers and enclosures providing during erection ?
A(4) 2.4.3.1. A(4) 1.2.3.4. A(4) 1.3.4.2. A(4) 3.2.4.1.

Q(5) A “ Tong tester “ is used to measure ?
A(5) Current : Voltage : Résistance : Frequency :

Q(6) If the person ordering Installation work is not the user then it is recommended that copies of the Electrical Installation Certificate must be given to ?
A(6) 1- the person ordering the work , 2- the person ordering the work and the user , 3- the person ordering the work and the local building authority , 4- the user and the local building authority ,

Q(7) Faults within existing Installations which “ do not “ effect new additions to the installation ?
A(7) 1- are required to be noted if observed by engineer doing the new additions ?
A(7) 2- are required to be corrected by the engineer doing the new additions ?
A(7) 3- do not need to be corrected by the engineer doing the new additions ?
A(7) 4 – are required to be reported to the local building authority by the additions ?

Q(8) when testing continuity of a ring final circuit wired with 2.5 / 1.5 pvc / pvc conductors using “ method 1 “ the value of ( R1 ) is 0.4Ω what should be the approximate value of ( R2 ) ?
A(8) a – 0.60Ω b – 1.00Ω c – 0.67Ω d – 0.16Ω

Q(9) the prospective short-circuit between line & neutral is measured at ( 900A) the maximum balanced prospective short-circuit current level between lines, as a rule of thumb , can be assumed to be approximately ?
A(9) a – 0.9kA b – 9 kA c - 90 kA d – 1.8 kA

Q(10) testing of CPCs is the testing of ?
A(10) a - insulation résistance b – continuity of main bonding conductors c - continuity of protective conductors d – earth fault loop impedance

Q (11) an instrument called a “ check box “ is sometimes used when ?
A(11) a – calibrating test instruments b – checking instrument battery voltage ? c – testing earth continuity d – comparing test results

Q(12) records of all checks , inspections & tests to an installation should be kept ?
A(12) a – for one year b – for 3 years c – for 10 years d – for the working life of the installation .

Q(13) when testing insulation of floors & walls the insulation must be able to withstand a test voltage ( a.c. rms ) of at least ?
A(13) a – 0.5kV b – 1.0kV c – 2.0kV 4.0kV

Q(14) IEE Guidance Note 3 recommends that for reliability on service the résistance of any Earth Electrode should be below ?
A(14) a – 0.35Ω b – 0.8Ω c - 100Ω d- 200Ω

Q(15) defects or omissions revealed during Initial Verification shall ?
A(15) a - be made good when the certificate is issued b - be made good after the certificate is issued
c - be made good within 30 days of the certificate being issued d - a - be made good before the certificate is issued

Q(16) the responsibility for comparing test results with relevant criteria during the verification of a new installation lies with ?
A(16) a – the design engineer b – the installation engineer c – the test engineer d – the client

Q(17) if the highest reading for ( r1 + r2 ) recorded while testing the continuity of ring final circuit conductors is 0.9Ω ,
What will be the value of ( R1 + R2 )
A(17) a – 1.8Ω b – 0.9Ω c – 0.45Ω d – 0.225Ω

Q(18) control gear and interlocks should be operated when carrying out ?
A(18 ) a – functional testing b – isolating testing c – polarity testing d – continuity testing .


PS – you will get the answers ,

 

[amberleaf]

Q19 - Table 9A in the On Site Guide gives a value of 19.51 (mΩ/m) for a line conductor of 2.5mm2 and a protective conductor of 1.5mm2. What would be the resistance of a circuit 25m in length when wired using these conductors:
A(19) a - 4.87 Ω. B - 487 Ω. C - 780 Ω. D - 0.487 Ω.
Q20 - If defects on an existing installation are found when carrying out alterations or additions the person responsible for issuing the ‘minor works certificate’ shall:
A - record the defects on the certificate so far as is reasonably practicable.
B - always record the defects on the certificate.
C - repair the defects before issuing the certificate.
D - record the defects on a separate document.
Q21 - Which of the following is ‘not required information’ which should be made available to the inspection and test engineer:
A - the maximum demand expressed in Amperes.
B - the name of the manufacturer of the electrical components .
C - the nature of the load current.
D - the type of earthing arrangement.
Q22 - For basic and fault protection using SELV and PELV systems, which of the following requirements is true:
A - The nominal voltage must not exceed 50V a.c. or 120V d.c.
B - The nominal voltage must not exceed 110V a.c. or 120V d.c.
C - The nominal voltage must not exceed 110V a.c. or 50V d.c.
D - The nominal voltage must not exceed 120V a.c. or 110V d.c.
Q23 - When carrying out an earth fault loop impedance test on a circuit the value for (R1 + R2) was found to be 0.3 Ω. A value for Ze was already recorded as 1.15 Ω. The value for Zs can be assumed to be:
A - 0.85 Ω. B - 1.15 Ω. C - 1.45 Ω. D - 1.18 Ω.
Q24 - Which of the following does not meet the requirements for maximum value of voltage drop on a 230V supply, supplied directly from a public low voltage system, as stated in Appendix 12 of BS 7671:
A - Lighting 5.9V; Sockets 8.2V.
B - Lighting 3.5V; Sockets 11.7V.
C - Lighting 6.8V; Sockets 5.3V.
D - Lighting 4.0V; Sockets 5.7V.
Q25 - Instrument calibration certificates are normally valid for:
A - 3 months. B - 6 months. C - 1 year. D - 2 years.
Q26 - The maximum prospective fault current recorded on an electrical installation certificate should be:
A - the greater of either the short-circuit current or the earth fault current.
B - the lesser of either the short-circuit current or the earth fault current.
C - the short-circuit current.
D - the earth fault current.
Q27 - When completing an installation certificate under ‘Number and Type of Live Conductors’, the 3-phase, 4-wire box should be ticked if the supply is:
A - 2-phase, neutral and earth.
B - 3-phase, and earth.
C - 3-phase and neutral.
D - four single phase supplies.
Q28 - When completing a Minor Works Certificate, which of the following is not an example of an ‘essential test’:
A - Prospective fault current. B - Earth fault loop impedance.
C - Insulation resistance. D - Polarity.
29 - Regional electricity companies quote a maximum likely value of external loop impedance (outside the consumer’s installation) for a TN-S system as:
A - 0.35 Ω. B - 0.8 Ω. C - 21 Ω. D - 200 Ω.
Q30 - A visual inspection of a new installation must be carried out:
A - upon completion
B - during testing
C - during erection
D - during erection and upon completion

 

[amberleaf]

C&G 2392-10 Fundamental Inspection, Testing and Initial Verification - Paper 4 :

Q1 - Low-resistance ohmmeters used for continuity measurements should have a no-load voltage and a short-circuit current of :
A(1) a - Voltage between 4V and 24 V; short-circuit current of 200 mA.
A(1) b - Voltage between 0V and 24 V; short-circuit current of 100 mA.
A(1) c - Voltage between 4V and 20 V; short-circuit current of 1 mA.
A(1) d - Voltage between 0V and 20 V; short-circuit current of 1 mA.
Q2 - The protective measure where basic protection is provided by insulation of live parts, barriers or enclosures and fault protection is provided by simple separation of the separated circuit from other circuits and from earth is called:
A(2) a - earth free equipotential bonding.
A(2) b - additional protection.
A(2) c - prevention of mutual detrimental influence.
A(2) d - electrical separation.
Q3 - When taking impedance measurements at ambient temperature a ‘Rule of Thumb’ correction factor may be applied to take into account the increased resistance of conductors due to load current. The recommended correction factor as indicated in BS7671 Appendix 14 is : ( hint ) p-361
A(3) a - 0.5. b - 0.75. c - 0.8. d - 1.2.
Q4 - The metal sheath of the supply cable is used as part of the earth return path in which of the following systems:
A(4) A - TT. B - TN-C. C - TN-S. D - TN-C-S.
Q6 - Which of the following statements is correct regarding double insulation being used for both basic and fault protection:
A(6) a - Basic protection is provided by basic insulation and fault protection is provided by supplementary insulation.
A(6) b - Fault protection is provided by basic insulation and basic protection is provided by supplementary insulation.
A(6) c - Basic protection is provided by both basic insulation and supplementary insulation.
A(6) d - Fault protection is provided by basic insulation and supplementary insulation.
Q7 - Put the following tests in the correct sequence: 1-earth fault loop impedance 2-phase sequence 3-prospective fault current 4- voltage drop:
A(7) a - 1.3.2.4. b - 2.4.1.3. c - 1.4.3.2. d - 4.1.2.3.
Q8 - Which of the following IP Codes signifies protection against total immersion in water:
A(8) a- IP 4X. b - IP 8X. c - IP X4. d - IP X8.
Q9 - An insulation resistance tester must be capable of delivering a test current of not less than:
A(9) a - 0.5 mA. B - 1.0 mA. C - 2.0 mA. D - 20 mA.
Q10 - The proposed interval between initial verification and the first periodic inspection should be recommended by:
A(10) a - the person carrying out the initial verification. b - the person who designed the installation.
c - the installation engineer. d - the client .
Q11 - Which of the following does not meet the requirements for maximum value of voltage drop on a 400V supply, supplied directly from a public low voltage system, as stated in Appendix 12 of BS 7671:
A(11) a - Lighting 11.1V; Sockets 19.6V. b - Lighting 4.7V; Sockets 22.3V.
c - Lighting 6.8V; Sockets 11.4V. d - Lighting 10.9V; Sockets 15.5V.
Q12 - Which of the following is not a method of ascertaining the prospective short circuit current at the origin of an installation:
A(12) a - Measurement. b - Calculation. c - Enquiry. d - Elimination.
Q13 - The test current applied to a 30mA RCD to check for a 40ms maximum disconnection time is:
A(13) a - 15mA. b - 30mA. c - 150mA. D - 300mA.
Q14 - Which of the following protection devices is unlikely to be suited for short circuit currents in excess of 6kA:
A(14) a - BS 3036 semi-enclosed fuse. B - BS 1361 cartridge fuse.
c - BS 88 general purpose fuse. d - BS EN 60898 circuit breaker.
Q15 - Which of the following statements is true:
A(15) a - A non-conducting location should contain protective conductors.
b - A non-conducting location should contain no protective conductors.
c - A non-conducting location should contain bonding conductors only.
d - A non-conducting location should contain extra-low voltage conductors only.
Q16 - When testing continuity of a ring final circuit wired with 2.5/1.5 PVC/PVC conductors using ‘Method 1’. The value of R1 is 0.8Ω, what should be the approximate value of R2 :
A(16) a - 1.20 Ω. B -2.00 Ω. C -1.34 Ω. D - 0.32 Ω.
Q17 - When using ‘protection by electrical separation’ the verification of live parts from those of other circuits and from Earth shall be confirmed by:
A(17) a - Earth continuity testing. b - Polarity testing. c - Functional testing. d - Insulation resistance testing.
Q18 - Which of the following is not permitted for use as an earth electrode:
A(18) a - Underground structural metalwork. B - Metal water mains pipes.
c - Lead sheaths of cables. d - Earth plates.
Q19 - When using a four terminal earth electrode tester to measure earth electrode resistance the connection to the earth electrode is made using terminals:
A(19) a - C1 and P1. b - C2 and P2. c - C1 and P2. d - P1 and C2.
Q20 - If the highest reading for (r1 + r2) recorded while testing the continuity of ring final circuit conductors is 1.2 Ω, what will be the value of (R1 + R2):
A(20) a - 2.4 Ω. B - 1.2 Ω. c - 0.6 Ω. d - 0.3 Ω.
Q21 - When subjecting a 30mA RCD to a test current of 150mA the protective conductor potential must not rise above a value of:
A(21) a - 50 V. b - 55 V. c - 110 V. d - 230 V.
Q22 - Which of the following tests would not normally be required during initial verification of an electrical installation:
A(22) a - RCD testing. b - Prospective fault current. c - Continuity of main bonding conductors. d - Verification of voltage drop.

Q23 - During earth loop impedance testing Ze is measured with the main bonding conductors disconnected whilst a live Zs test is carried out with the bonding conductors connected. This often leads to unexpected readings whereby the value of Zs can be lower than Ze. This is normally assumed to be because of:
A(23) a - parallel earth paths during the Zs test. b - parallel earth paths during the Ze test.
c - less conductor distance during the Zs test. d - less conductor distance during the Ze test.
Q24 - During initial verification of a TN system the installation earth conductor was recorded as 16mm2. The minimum size of main bonding conductor should be:
A(24) a - 4mm2. b - 6 mm2. c - 10 mm2. d - 16 mm2.
Q25 - When carrying out an earth fault loop impedance test on a circuit the value for (R1 + R2) was found to be 0.4 Ω. A value for Ze was already recorded as 1.2 Ω. The value for Zs can be assumed to be:
A(25) a - 0.4 Ω. b - 0.8 Ω . c -1.2 Ω. d - 1.6 Ω.
Q26 - During earth electrode resistance testing the current test spike is placed 30 metres from the earth electrode under test. The potential test spike is placed midway between the earth electrode and the current spike. The potential spike would then normally be moved a distance each way of approximately:
A(26) a - 1 metre. b - 3 metres. c - 6 metres. d - 15 metres .
Q27 - The prospective short-circuit current between line and neutral is measured at 850 A. The maximum balanced prospective short-circuit current level between lines, as a rule of thumb, can be assumed to be approximately:
A(27) a - 0.85 kA. b - 1.7 kA. c - 8.5 kA. d - 17 kA.
Q28 - The schedule of test results certificate shown in both BS 7671 and Guidance Note 3 requires completion of the:
A(28) a - (R1 + R2) and R2 columns . b - (R1 + R2) or R2 column.
c - (R1 + R2) columns only. d - R2 column only.
Q29 - During inspection, a circuit breaker to BS EN 60898 was seen to have a small rectangular box with the value 6000 marked within. This figure represents:
A(29) a - the current required to activate the device. b - the rated short-circuit capacity of the device in kA.
c - the current, in amps, expected during a short-circuit fault.
d - the rated short-circuit capacity of the device in Amps.
Q30 - When completing an Inspection Schedule, where an inspection was not carried out, the relevant box must be completed using a:
A(30) a - √ - NOW CLICK 'BACK' TO TRY AGAIN. b - X - NOW CLICK 'BACK' TO TRY AGAIN.
c - N/A - NOW CLICK 'BACK' TO TRY AGAIN. d - LIM - NOW CLICK 'BACK' TO TRY AGAIN.

 

[amberleaf]

TN-C-S Systems
Not Allowed in Certain Locations i.e. Petrol Stations

( PME ) Important to Ensure that the Neutral is kept at Earth Potential by Earthing it at Many Points along its Length ( Hence “ Multiple “ Earthing )

If this is Not done “ a Fault to Neutral in One Installation could Cause a Shock Risk in all the Other Installations Connected ,

Concentric Cable : Single Core Cable Armouring , ( PEN ) Line / Neutral & Earth Combine ,
Single-Phase Split Concentric Cable with Stranded Copper Phase Conductors and Copper Wire Neutral & Earth Continuity Conductors 600 / 1000V

Domestic Inspection & Testing : 2392-10

( 612.9 ) Where Protective Measures are used which Require a Knowledge of Earth Fault Loop Impedance , the Relevant Impedance shall be Measured . or Determined by an Alternative Method :

External Earth Fault Loop Impedance , ( Ze )

( Safe Working Procedure ) Regulation ( 12 ) “ EAWR – 1989 “ ≈ ≈ ≈ ( Lock Off ) ≈ ≈ ≈

( Caution !! Electrician at Work do Not Switch On )

The First off Our ≈ Live Tests ≈ is ( “ Earth Fault Loop Impedance “ ) Determing External : Ze ←
This is a ( Live Test ) Which Can only be Measured by Testing as Near as Possible to the Origin of the Instillation

The Earthing Conductor has to be Disconnected from the Earthing Terminal ( 16mm2 ) to Eliminate Parallel Paths on the Installation Side ,
There for It is Essential for Safety Reasons for the Entire Installation to be Isolated form the Supply before doing this ,

Instrument : No-Tip Loop Tester :

3 – Leads Used ,

Green Lead Onto the Main Earthing Conductor Which is Disconnected : ← 1st
Blue Lead Onto the Supply Side of Main-Switch , ← 2nd
Brown Lead Onto the Supply Side of Main-Switch ,

Turn the Instrument On : This will Give me the “ Voltage “ ( and the “ Polarity “ is Correct : 241V Press the Loop Test : 0.66Ω *
Transformer Must be Quiet a Distance away ,

It is Good Practice to Repeat the Test Again ← ← ←

Green Lead Onto the Main Earthing Conductor Which is Disconnected : ← 1st
Blue Lead Onto the Supply Side of Main-Switch , ← 2nd
Brown Lead Onto the Supply Side of Main-Switch ,

Turn the Instrument On : This will give me the “ Voltage “ and the “ Polarity “ is Correct : 242V Press the Loop Test : 0.66Ω

Take the Highest of the Two Readings : ( 0.69Ω ) *

Re-Connect the Earthing Conductor back Onto the Terminal

I’ll be Recording this in the box , I’ll be putting This Onto the Test Certificate ( Schedule of Test Results )

It’s a Good Idea to take a Photo-copy of Certificate on site , any Alterations can be put Onto the ( Original Schedule of Test Results ) at Home

Archive for the '2391 - how to test' Category

Continuity of Final Circuit Conductors – Radial
Please note that this is a dead test and the circuit must be isolated when testing
Top be carried out on radial circuits to ensure the CPC of the circuit is undamaged and connected throughout the circuit
The highest reading should be obtained from the furthest part of the circuit. If the highest reading appears not to […]

September 2nd, 2008 | Posted in 2392 – how to Test / No Comments

Continuity of Bonding Conductors :
1. Safely isolate the supply
2. Disconnect one end of the conductor, preferably the end at the consumer unit.
3. (Null out test leads) or ( record and remember to subtract from end result)
4. Connect one test lead at the consumer unit’s disconnected end
5. Connect the other test lead to the metal work of which the conductor […]

September 2nd, 2008 | Posted in 2391- how to Test / 2 Comments

Test 1B Testing – Continuity of the Protective Conductors :
Description of test
Performing this test is to ensure that there is continuity throughout the circuit, that there are no breakages and conductors have been connected correctly. Be sure you have isolated the supply before beginning the test.

Methods
Test method 1 : Short lead Test
Test method 2 : Long lead Test

Test Equipment
Low Ohm Resistance Ω

PFC : 2391-

Perspective fault current
1. This is a live test
2. set Instrument to PFC test
3. Place one probe on the incoming Neutral conductor
4. Place the other probe on the incoming Line conductor
5. Test and record result
Note: some three lead tests will need the 3rd test lead to be connected to the main earthing terminal

Insulation Resistance Testing : 2391-

an insulation resistance test is like a pressure test of the circuits. On a 230v circuit, a test voltage of 500 volts is sent down. We do this test to check for current leaks in the insulation, hence “insulation resistance test”. Current leaks could occur from anything such as old age to crushed cables
Information to consider when doing an insulation resistance test
- As 500v volts is being sent down the circuit, if the building is occupied , then all must be informed
- Remember to remove all lamps for fittings because lamps could blow and effect readings
- if it is not possible to remove a lamp from a fitting, ensure the switch is open
Ensure
- dimmer switches are removed (why?)
- Accessories with neon indicator lamps are switched off (why?)
- Pir’s are removed (why?)
- All fixed equipment isolated (ovens, TV’s, why?)
- Shaver sockets removed (why?)
- Electrical portable items are unplugged (why?)
1. Safely isolate the supply
2. remove equipment mentioned above
3. Set insulation resistance tester to 500v
4. Set instrument to 200Mohms if it is not self ranging
5. Test between Neutral & Line
6. Test between Line & CPC
7. Test between Neutral & CPC
note: lighting circuits should be tested with the switches on and while operating all 2 way switching in both positions.
note: If testing the whole board at the tails then you need the supply to the board OFF i.e. its main switch and tails de-energised and the board’s main switch in the ON condition.
note: If the supply to the board cannot be removed just lock the main switch off at the board and test the whole installation from the switched side of the isolator. (Now dead/use proving unit before and after

Earth electro Test : 2391-

Note: this is a live test
1. Safely isolate installation
2. Ensure the earth electro is connected to the main earthing terminal
3. Disconnection main earthing
4. Connect one probe of the earth loop impedance tester to the main disconnected earthing conductor
5. Use the other probe to connect to the incoming side of the Line conductor
6. Perform Test and record result
7. Reconnect Main earthing terminal

Earth Fault loop impedance Test Ze : 2391-

note: This is a live test
Ze can be remembered as Z external (Ze)
1. Safely isolate supply
2. Disconnect the earthing conductor
3. Set test metre to loop test (20 ohms)
4. One test probe shall be placed on the incoming Line conductors
5. The other test probe shall be connected to the disconnected main earthing conductor (3 lead test shall be referred to the manufactures manual, in some cases the 2 leads (green & black) shall be connected to each other
6. Test and record result
7. Reconnect the earthing conductor
( Zs= Ze + ( R1+R2 )

Dead Polarity Test : 2391-

- Polarity testing is to ensure that all protective devices are connected in Line conductors of the circuit
- If the test “continuity of circuit protective conductors” has already been completed. Then polarity has been correctly proved
1. Safely Isolate Circuit
2. The circuit you are testing for polarity shall have the CPC & Line conductors cross-connected at the origin of the circuit (Consumer Unit)
3. At the furtherest point of the circuit you are testing, a test shall be made between the CPC & Line. This means if testing ed a cooker, the switch should physically removed and tested on the incoming side of the switch.
4. A further check should be made, by removing the cross connected CPC & Line conductors at the Consumer Unit and performing the same test again (the reading should be high as the circuit is open). This shall proved that you are testing the correct circuit.
note: this test can be preformed at the ceiling rose on a light circuit, or at the switch

 

[amberleaf]

Continuity of Ring Final circuit conductors – Ring : 2391-

note: To ensure the cables form a complete ring throughout and that every point is correctly connected in the correct polarity and has no interconnections
1. Safely isolate supply
2. Test continuity between the ends of the Line conductor and record value
3. Test continuity between the ends of the Neutral conductor and record value
4. Test continuity between the ends of the CPC conductor and record value
5. Join leg 1 of Line to leg 2 of Neutral
Now test between leg 2 of Line and leg 1 of Neutral
Note: that the resistance will be double of the single line conductor
6. Now join both legs which you just tested from
leg 1 of Line and leg 2 of Neutral joined
leg 2 of Line and leg 1 of Neutral joined
Testing between the jointed legs should give a reading of a half of the line conductor
7. Leave ends joined as in step 6
8. Test at each socket of the circuit between Line and Neutral note: all readings should be the same
Readings which tend to higher may have incorrect polarity at one of the sockets, but further investigation should proceed.
10. Repeat step 10 using CPC and Line
leg 1 of Line and leg 2 of CPC joined
leg 2 of Line and leg 1 of CPC joined
Record results
note: If there are any spurs on the circuit, it will be more than likely that the readings of them are the highest, and these ones should be recorded for your r1 + r2

Continuity of bonding conductors : 2391-

1. Safely isolate the supply
2. Disconnect one end of the conductor, preferably the end at the consumer unit.
3. (Null out test leads) or ( record and remember to subtract from end result)
4. Connect one test lead at the consumer unit’s disconnected end
5. Connect the other test lead to the metal work of which the conductor you are testing is connected to (ensure any painted metal work has been scratched off, to make a solid connection) by not connecting it to the clamp will prove that the integrity of that clamp is efficient enough/correct BS 951
6. Test
- the result will give the total resistance of the conductor (remembering to subtract the test lead resistance, if not previously nulled out)
7. Re connect bonding conductor

Live Polarity Test 2391-

Note: An approved voltage indicator shall be used or test lamp to GS38
1. This is a live test
2. Using the approved voltage indicator, one probe shall be placed on the incoming neutral, and the other on the incoming line conductor, on the main breaker. The indicator should how it is live
3. One probe shall now be placed on the CPC and the other on the incoming line conductor. The indicator should show it is live
4. A test shall be preformed between CPC & incoming neutral. The indicator should indicate that it is not live
Note: If the indicator produces results different to expected results above, the further investigation shall be taken

Continuity of Final circuit conductors – Radial : 2391-

Please note that this is a dead test and the circuit must be isolated when testing
Top be carried out on radial circuits to ensure the CPC of the circuit is undamaged and connected throughout the circuit
The highest reading should be obtained from the furthest part of the circuit. If the highest reading appears not to be at the end of the circuit, then further investigation should proceed (It maybe because of how the circuit was installed, although one end may appear to be closer to the CU than other points, it may still be the end of the circuit)
1. Safely isolate supply
2. Cross connect the Line and CPC at one end of the circuit, preferably at the consumer unit
3. At each point of the circuit, a test should been made between Line and CPC
4. The highest reading will determine the R1 + R2 value of the circuit
note: when the Line and CPC conductors are the same size, the total resistance can be simply divided by 2 to find the resistance of just the CPC
In most cases Twin & Earth is used and the size of the CPC is smaller than the Live conductors, therefore this equation should be used to determine the size of the CPC.
eg. Total resistance r1 + r2 = 0.35 ohms
r2= 0.35 x (2.5/(2.5+1.5))

Criticism :

The final ring-circuit concept has been criticized in a number of ways, and some of these disadvantages could explain the lack of widespread adoption outside the United Kingdom.
The only way to see the pros and cons of ring circuits is to compare them to the other option: radials.
Fault conditions are not apparent when in use
Ring circuits continue to operate without the user being aware of any problem if there are fault conditions or installation errors that make the circuit unsafe:
• Part of the ring missing or loose connections result in 2.5 mm2 cables running above rated current at times, resulting in reduced cable life.
o Radials with a loose connection will overheat severely and be an immediate fire risk.
o Radials with a broken connection will not function (if L or N broken), or function with no safety earth connection (if Earth broken).
• Accidental cross connection between two 32 A rings means that the fault current protection reaches 64 A and the required fault disconnection times are violated grossly.
o Testing at installation addresses this.
• Ring spur installations encourage using three connectors in one terminal, which can cause one to become loose and overheat.
o The same situation occurs with both radial and ring circuits when branching off is used.
• Rings encourage the installation of too many spurs on a ring, leading to a risk of overheating, especially if spur cables are too long
Complexity of safety tests
Testing ring circuits takes 5–6 times longer than testing radial circuits .The installation tests required for the safe operation of a ring circuit are substantially more time consuming than those for a radial circuit, or electricians qualified in other countries may not be familiar with them.

Archive for the '2 way switching' Category

2 Way Lighting : FOR APPRENTICES ,
Here we’ll explain how to do 2 way lighting

o———o …………………….. 0—————-0 ↔ ( the dots are to stop drawing move ) Experiment !!!
………. 0—————————o

The diagram shows single colours only. In real life these wires would be covered by an outer protective sheath and would include a bare earth wire and would be called a cable.
Brown sleeving or tape would of been placed on the wires as shown to show

Steel Armoured Cable info -

Hello, just a little information about Steel Armoured Cable (SWA)
Steel Armoured Cable is protected by a sheath of galvanised steel. This makes it suitable for direct burial, cable ducting or it can be surfaced mounted without any further protection. It can be used for indoors and outdoors.
Steel Armoured Cable (SWA) Cores Colours 3-core / 4- core
* there’s some old ( 2-core still out there )

RCD main switch + MCBs ( Non-Split Boards :

Having a Consumer Unit with an RCD as a Main switch and just MCBs, not on a split board contravenes the regulations in the 17th Edition under reg, 314.1 (see also 314.2 )
An Rcd as a main switch when tripped due to the failure of a circuit or due to nuisance tripping will affect all other

The IEE recently published the 17th edition Wiring Regulations, (BS 7671), which came into force in
July 2008. Candidates are expected to have knowledge of the 17th edition wiring regulations, and
must answer questions accordingly.
The unit and complex numbers were amended from June 2008 onwards to signify that the
qualifications meet 17th edition requirements.

2391-01 became 2391-10
2391-02 became 2391-20
Unit 101 is now 301
Unit 102 is now 302
Unit 201 is now 303
Unit 202 is now 304

Other than the wiring regulation updates, the content of this qualification remains unchanged.
Important:
Candidates who have passed units under the old regulations (i.e. they already hold 101, 102, 201 or 202) do not need to re-sit under the new unit numbers.

 

[amberleaf]

Drawings and labels 2391- march 2009

Question 25 required candidates to provide a fully labelled diagram of the earth fault loop path for a
radial circuit. The scenario identified the system as TN-S. Whilst some candidates used the
incorrect system there was a general lack of clear drawing and labelling.
Section A
In Section A there were many fundamental errors identified in candidate responses. Typically many
candidates
•
identified a shock risk when testing main protective bonding conductors and not the tripping
hazard. If the procedure is correct (isolation of the installation) there is no shock risk.
•
could not correctly identify the reason for carrying out a continuity of ring final circuit test.
•
could not identify special locations which were classified in zones; this including listing locations
such as caravan sites and construction sites.
•
were unaware of the IP requirement for Basic Protection with most examples related to ingress
of liquids.
•
were unable to determine the recorded RA value from given data, many adding the three values
in parallel.
•
did not know why R1 + R2 cannot be determined using Zs – Ze. Despite this information being
given in Question 16 of Section A, many then went on in Section B to determine R1 + R2 using
this incorrect method.
•
were unable to identify the connection points for the instrument leads when measuring Ze when
using a three lead test instrument.
•
could not determine the maximum Zs for a 300 mA RCD to meet the requirements of BS 7671
•
could not correctly determine the maximum permitted voltage drop for given circuits. Many
used 16th edition values and/or determined voltage at equipment terminals.

Section B
In Section B there were some areas where candidates were unable to demonstrate their
understanding of the subject.
Many candidates were unable to
•
identify operational aspects which would affect the inspection and testing activity with many
simply identifying locations which were given in the scenario without identifying the aspect.
•
identify the correct test sequence and relate instruments and ranges for the tests. For a radial
final circuit the candidates included main protective bonding conductors, ring final circuit
continuity and polarity with an approved voltage indicator in the dead tests, and PFC and RC in
the live tests.
•
describe the ring final circuit continuity test with may carrying out Stage 2 & 3 linking one pair
(L1 & N2) and testing across the other pair for each test. Some included this as an extra stage
wasting time and effort. A number were unable to determine the expected values.
•
determine the calculated values of R1 and R2 correctly with a surprising number incorrectly
using Zs – Ze despite the information in Part A that this method could not be used. Most
candidates failed to appreciate that two of the circuits were ring final circuits and therefore
failed to divide their result by 4.
Exam technique – time management
Time management for candidates is important to ensure they have an opportunity to achieve the
best possible result. Considering the number of marks available for each question and using this
determine the extent and depth of the answer required would be useful.
Page 8
As a guide, candidates should spend approximately one minute on an answer for each possible
mark to be awarded. A question worth three marks for example should take approximately three
minutes to complete. However many questions in Section A will take considerably less than this.
Exam technique – read the question
Careful reading of the question is important. Many answers did not include the information
requested and candidates often provided answers which did not correspond to the question posed.
Candidates often did not answer the questions in both Sections A and B of the paper in relation to
the given information and this often resulted in the loss of marks. Candidates must read the
information given in the question.

Many candidates did not display the required knowledge when answering the questions and this
would suggest they do not have the necessary knowledge, understanding and experience when
entering this qualification.
Use of correct terminology
Correct terminology must be used when answering questions. Candidates continue to use incorrect
terminology. This does indicate that candidates are not aware of the underlying requirements and
processes. Typically candidates still referred to a periodic inspection and testing report as the type
of inspection and the Electricity at Work Regulations is still incorrectly referred to as the Electricity at
Work Act. Candidates also continue to use incorrect titles for documents and publications and to
use inappropriate titles for the forms of certification.
Documentation
Some candidates were unable to identify the correct title of documents for certification, and many
still refer to a Periodic Inspection Certificate. Candidates were unable to correctly identify the

Schedules by title with a Schedule of Items Inspected and a Schedule of Tests being common
incorrect alternatives.
Questions which required candidates to identify where information is to be recorded on the forms
of certification produced results which appear to indicate the candidates are not familiar with both
the compilation and the content of these forms.
Many candidates did not consult with the third party (licensing authority) when determining the
extent and limitations.
Inspection
Question 22 asked candidates to identify three particular areas for investigation during inspection
due to the nature of the location in the kitchen, laundry and residents rooms. The responses to this
question were exceptionally poor with many candidates simply listing items such as sockets and
switches for all locations giving no indication of the particular areas of investigation. Others
included tests and many demonstrated a lack of understanding of the requirements for the
locations. Many believed that some type of non-specific bonding was required.
Considering the information provided in the scenario there were very few candidates who identified
inspection related to corrosion, appropriate IP ratings damage and the like. In the residents rooms
many candidates considered the equipment being PAT tested etc as appropriate items for their
inspection.
The response to this question generally indicated a lack of understanding of the inspection process
and the information provided in GN3 related to the inspection of installations.
Question 4 required candidates to identify reasons why a survey would be required before a
periodic inspection could be undertaken. Very few candidates were able to identify the relation to
information not being available. Most identified events that could give rise to a periodic inspection
being required.
Testing
The common misunderstandings identified above show that ring final circuit testing is still a problem
for many candidates. There is also some confusion as to the required tests fro particular circuits
with many quoting the standard list, and the range of values expected for the tests undertaken. The
test process and the expected results are fundamental to the requirements of those undertaking
inspection and testing and for the candidates to complete the practical assessment.
Calculations
Many candidates had problems with calculations related to the inspection and testing process.
Cumulative insulation resistance values, determining values for stage 2 and stage 3 of the ring final
circuit continuity test from given information caused some difficulty. These calculations are typical
of the type of evaluations which may be required during the verification of test results. As these are
fundamental to the activities of initial verification and periodic reporting such calculations should be
within the abilities of the candidates. It would appear that a number of candidates do not
understand the effects of resistances in series and parallel.
Describing test procedures
When describing how to carry out a test, candidates were often confused as to what was required,
unable to describe a logical approach and rarely used large clear diagrams to assist with their
description.

Use of correct terminology

Correct terminology must be used when answering questions. Candidates continue to use incorrect
terminology. This does indicate that candidates are not aware of the underlying requirements and
processes. Typically candidates still referred to a periodic inspection and testing report as the type
of inspection and the Electricity at Work Regulations is still incorrectly referred to as the Electricity at
Work Act. Candidates also continue to use incorrect titles for documents and publications and to
use inappropriate titles for the forms of certification.
Documentation
Some candidates were unable to identify the correct title of documents for certification, and many
still refer to a Periodic Inspection Certificate. Candidates were unable to correctly identify theSchedules by title with a Schedule of Items Inspected and a Schedule of Tests being common
incorrect alternatives.
Questions which required candidates to identify where information is to be recorded on the forms
of certification produced results which appear to indicate the candidates are not familiar with both
the compilation and the content of these forms.
Many candidates did not consult with the third party (licensing authority) when determining the
extent and limitations.

 

[amberleaf]

Inspection

Question 22 asked candidates to identify three particular areas for investigation during inspection
due to the nature of the location in the kitchen, laundry and residents rooms. The responses to this
question were exceptionally poor with many candidates simply listing items such as sockets and
switches for all locations giving no indication of the particular areas of investigation. Others
included tests and many demonstrated a lack of understanding of the requirements for the
locations. Many believed that some type of non-specific bonding was required.
Considering the information provided in the scenario there were very few candidates who identified
inspection related to corrosion, appropriate IP ratings damage and the like. In the residents rooms
many candidates considered the equipment being PAT tested etc as appropriate items for their
inspection.
The response to this question generally indicated a lack of understanding of the inspection process
and the information provided in GN3 related to the inspection of installations.
Question 4 required candidates to identify reasons why a survey would be required before a
periodic inspection could be undertaken. Very few candidates were able to identify the relation to
information not being available. Most identified events that could give rise to a periodic inspection
being required.

Testing

The common misunderstandings identified above show that ring final circuit testing is still a problem
for many candidates. There is also some confusion as to the required tests fro particular circuits
with many quoting the standard list, and the range of values expected for the tests undertaken. The
test process and the expected results are fundamental to the requirements of those undertaking
inspection and testing and for the candidates to complete the practical assessment.
Calculations
Many candidates had problems with calculations related to the inspection and testing process.
Cumulative insulation resistance values, determining values for stage 2 and stage 3 of the ring final
circuit continuity test from given information caused some difficulty. These calculations are typical
of the type of evaluations which may be required during the verification of test results. As these are
fundamental to the activities of initial verification and periodic reporting such calculations should be
within the abilities of the candidates. It would appear that a number of candidates do not
understand the effects of resistances in series and parallel.
Describing test procedures
When describing how to carry out a test, candidates were often confused as to what was required,
unable to describe a logical approach and rarely used large clear diagrams to assist with their
description.

Inspection & Testing Methods

Testing - Sequence of Tests : GN-3
1. Continuity of protective conductors ( 612.2.1 )
2. Continuity of Ring Final Circuit Conductors ( 612.2.2 )
3. Insulation resistance ( 612.3 )
*. Protection by SELV / PELV or by Electrical Separation ( 612.4 )
* . Basic Protection by barriers and enclosures ( 612.4.5 )
4. Insulation Résistance / Impedance of Floors & Walls ( 612.5 ) - look p-62
5. Dead ↔ Polarity ( 612.6 )
6. Earth electrode resistance (Ze) ( 612.7 )
* . Live Polarity of Supply
Test Following Installation being Energized

1. Earth fault loop impedance (Ze) (Zs) ( 612.9 ) 2. Additional Protection ( RCD 612.10 ) 3. Prospective fault current (PFC) ( 612.11 )
4. Functional testing ( 612.13 )

Domestic Inspection & Testing : 2392-10

Additional Protection by Residual Current Devices ,

( DANGER LIVE TEST )

Domestic Installations Installed to meet the Requirements’ of the 17th Edition
Are likely to have more than One Residual Current Devices , whether a Standard RCD or devices such as RCBOs
The effect of those devices need to be verified by appropriate Visual Inspection and Tests

Many Instruments these days do the full range of Test Automatically

* Plugging Into the Socket-Outlet from Instrument *

The First Test is Undertaking at the Rated Current of RCD so the Instrument Set to Times - ( x1 ) the RCD should Operate ( and it has - 7.6 mS )

For General Purpose RCDs to BS-4293 / Operating time Less than 200mS ( Remember BS- 200mS ) ← *
RCDs to BS-EN 61008 & BS-EN 61009-1 / Operating time below 300mS ( Remember BS-EN 300mS ) ← *

S / Type RCDs ( BS-EN 61008 - BS-EN 61009-1 ) Operating time between 130mS & 500mS ( Regs: p-243 – table 3A )

Circuit-Breakers : ( Regs: p-243 )

Type : B to BS-EN 60898 and the Overcurrent Characteristics of RCBOs to BS-EN 61009-1 ( fig 3.4
Type : C ( fig 3.5 / 61009-1
Type : D ( fig 3.6 / 61009-1

Time Delayed RCDs Operate between ( 200mS + 50% ---- 200mS + 100% )

It “ Not a Requirement ” of the Regulations am going to repeat the Test on both parts off the Supply Wave Form ( ≈ 0º / 180º ≈ )

Instrument Set RCD - on x1 ( 180º ≈ 8.7mS ) the One you Recording is the Longest of the 2 Times
The Next Part of the Test is the x5 times Current Test , for RCDs Not Exceeding 30mA ( Provide For Additional Protection Against Electrical shock )
With the x5 time Multiplier selected so that’s 5x 30mA which Equates to a Test Current of “ 150mA “ ( the RCD should Operate within 40mS
And it has ( Oº ≈ 5.5 mS ) both parts off the Supply Wave Form , the One you Recording is the Longest of the 2 Times

Although Not in the Regulations am going to do “ Half Current Test “ the RCD should Not Operate ( ½ 1 ) > 1999 mS
This Test helps to Check the Sensitivity of the device ,

The Test Button :

Following the Electrical Test procedure described above , each RCD should be Operated by means of its integral Test Facility .
This confirms that the device is responding to its design level of sensitivity and that all the mechanical parts are functioning .
The users of the Installations are advised ( by means of a notice at or near the origin of the Installations – Regs : 514.12.2 )



→ C&G 2392-10 Fundamental Inspection, Testing and Initial Verification - Paper 3 / 4
You’ll have the answers on Sun / Mon , ←

Domestic Inspection & Testing : 2392-10

Check of Phase Sequence and Verification of Voltage Drop ,

The 17th Edition introduced two new Test Requirements ( Part 6 ) the First is Checking Phase Sequence ,
Checking is for Installations with Multi-Phase Circuits Only , but shall be Verify that the Phase Sequence is maintained though the Installation ( 2392-10 So as we are Single Phase here This Test is Not Applicable )

The Second New Requirement is for Verification of Voltage Drop ( 612.14 ) which its not normally Required during Initial Verification because you should have the Design Information at hand it should take into account Voltage Drop so there’s no need to do it here

Low-Voltage Installation : 17th Edition , 3% Lighting / 5% Power

( 612.14 ) Two-Ways to Verify the Voltage Drop ← * (1) Evaluate the Voltage Drop by Measuring the Circuit Impedance :
* (2) Evaluate the Voltage Drop Using Calculations :

Evaluation of Voltage Drop by → Measuring ← Circuit Impedance : 2392-10 / 2391-20

( 612.14 ) Work Example , (1)

Suppose that it is desired to verify that the voltage drop does not exceed 5% in an existing single-phase 230V , 50 Hz radial circuit supplying a 20A heating load connected at the end of the circuit , the circuit is supplied directly from a distribution board at the origin of the installation , the line and neutral conductors of the circuit have thermoplastic ( pvc ) insulation and their résistance ( R1 + R2 ) is 0.3Ω when measured at ambient temperature ( say 20º C )

As the circuit rating does not exceed 100A and the supply frequency is 50 Hz , ( R1 + Rn ) may be taken to be the circuit impedance ( that is, inductive reactance may be ignored )

To evaluate the voltage drop . the measured value of ( R1 + Rn ) should be increased on the basis of the increase in conductor temperature due to load current , and then multiplied by the design current of the circuit ( Ib ) ← in the absence of better information , a correction factor of ( Cf 1.2 ) ← should be used to increase the conductor résistance in this case . this assumes an increase in conductor temperature from ( 20º C ) ( ambient ) to ( 70º C ) ( the maximum permitted operating temperature for thermoplastic insulated conductors )

The voltage drop ( Vd ) for the single-phase circuit in this example is therefore given by :
( Vd ) = measured value of ( R1 + Rn ) x 1.2 x ( Ib ) ←

Therefore ……. ( Vd ) = 0.3Ω x 1.2 x 20A = 7.2 V .

A voltage drop of 7.2V is equivalent to 3.13% ( given by 100% x 7.2 ÷ 230V )
It has therefore been verified that , in the case of this example , the voltage drop in the circuit does not exceed ( 5% ) ←

Calculators’ Out Chaps ?

→→→ ( R1 + Rn ) is 0.3Ω when measured at ambient temperature ( say 20º C ) ←←← Ops “

 

[amberleaf]

Evaluation of Voltage Drop Using Calculations : 2392-10 / 2391-20

( 612.14 ) Work Example , ( 2 )

The calculation method in regulation ( 612.14 ) as an example . ii to use diagrams or graphs showing maximum cable length
Versus load current for different conductor sizes with different percentage voltage drops for specific nominal voltages ,
Conductor temperatures and wiring systems

In the absence of such diagrams or charts , the voltage drop for a circuit may be calculated by using the tabulated values of voltage drop given in Appendix 4 of BS-7671 , in accordance with the instructions given in item 6 of that appendix , to do this , it will be necessary to ascertaining the type and size of cable by inspection , and to estimate the length of run for the circuit .

Insulation Résistance : ( New Installation Only ) This is Based on No-Power in the Building Yet :

Main Switch and all RCDs & MCBs are OFF ( Dead Test )
Inspection & Testing : 2392-10
61 : shall be applied when Verifying Insulation Resistance between non-earthed protective conductors’ and Earth

Where Surge protective devices ( SPD ) or other equipment are likely to influence the verification test , or be damaged , ←
( SPD ) – 250v dc . > 0.5MΩ

→ This is What Would Happen if there was a ( SPD ) fitting Over looked on a Circuit , ≈ ≈ ≈ ≈
Instrument 0n 500 dc / 0.1 MΩ ←←

Instrument 0n 500 dc / 0.1 MΩ
Lead on Neutral / Line Reading - 0.71MΩ , Which is a Fail
This is typical of Devices in the Circuit Effecting the Reading
You will have to go through Each Circuits Individual till you find the Fault ,
Once you find the ( SPD ) Fault Isolate the Circuit : MCB is switch off .
Re-do the Test with 500v dc your Readings are 99.9MΩ you have an a settable Value

Minimum Values of Insulation Resistance Listed in the Wiring Regs , ( 1MΩ is just an Exam Question ) in reality if I was getting readings any way near that Low on a New Installation
I would be doing further Investigations ,

SELV / PELV . Tables 61 ( Could be Lighting in the Bathroom 12Volts )
If the Circuit is ( SELV / PELV ) if it have equipment wired in ( SELV / PELV ) Test Voltage can be 250 V dc
Minimum Insulation Résistance ≥ 0.5MΩ

Remember that : Any Circuits Protected by RCBO will need to have RCBO Aux Tail Removed for Testing ← ←
RCBO Aux Tail must be Re-Connected after Testing

( 612.3.3 )
Where the circuit includes Electronic Devices which are likely to influence the results or be damaged .
Only a Measurement between the Live Conductors Connected together and the Earthing arrangement shall be made ,

Description of test RE- 2391-10

Performing this test is to ensure that there is continuity throughout the circuit, that there are no breakages and conductors have been connected correctly. Be sure you have isolated the supply before beginning the test.

Methods
Test method 1 : Short lead Test
Test method 2 : Long lead Test

Test Equipment
Low Ohm Resistance Meter

Note: R1 = Resistance of Line conductor, R2 = Resistance of CPC, Rn = Resistance of Neutral

Test Method 1: Short Lead Test
A Typical example would be to cross connect the Line and CPC conductors at the distribution board of the circuit going to be tested. At each point of the circuit, at test between Line & CPC should be performed. Noting that as you perform the tests further away from the cross connected ends at the distribution board, the higher the reading will become. The result recording the highest reading will be the R1 + R2 value on the test sheets. Make sure the test leads have been nulled on the tester or subtracted from the results accordingly

Test Method 2: Long Lead Test
This test is slightly different to method 1, as you are only testing the CPC. It is known as a long lead test because you may have to use an extra long cable to reach both ends of the CPC. ( Twin & earth can be used to create an extra long test lead). Making sure you null out the test leads before the test.
So basically what you have is your test meter connected to the Cpc at the distribution board and the other (extra long test lead, if necessary) test lead connected to the other end of the circuit. Perform the test, and record the highest result as the R2 value.

Sample Questions – 2392-10
Fundamental Inspection , Testing & Initial Verification – paper ( 3 )

1-C , 2-D , 3-B , 4-A , 5-A , 6-B , 7-A , 8-C , 9-D , 10-C , 11-A , 12-D , 13-C , 14-D , 15-D , 16-C , 17-D , 18-A ,
19-D , 20-A , 21-B , 22-A , 23-C , 24-B , 25-C , 26-A , 27-C , 28-A , 29-B , 30-D ,

Your Score should be 30 out of 30 :

Important Changes to Terminology and Definitions with the 17th Edition : 2392-10 / 2391-10

Among the changes to the scope and fundamental principles of the regulations is the inclusion of four new regulations for the protection of persons and livestock against voltage disturbances and electromagnetic influences.
There is also a specific requirement for appropriate documentation for all installations.
Of particular interest to the health and safety manager, Regulation 134.2.1 requires that inspection and testing must be carried out by a 'competent person' to verify that standards have been met.
Importantly, a 'competent person' is defined as someone 'who possesses sufficient technical knowledge and experience for the nature of the electrical work undertaken and is able at all times to prevent danger, and where appropriate, injury to themselves and others'.
In practice, this means that inspection and testing should only be taken by experienced engineers that are qualified to the City and Guilds 2392 - 10 course 'Fundamental Testing, Inspection and Initial Verification'.
This course is now recognized as the qualification for competent persons carrying out initial inspection and testing of electrical installations.
For periodic inspection and testing, competent persons should successfully complete the C and G 2392 - 20 'Inspection, Testing and Certification of Electrical Installations' course in addition to the 2392 - 10 course.
Once the initial verification of the installation has been completed, which includes both inspection and testing, the regulations call for the issuing of an Electrical Installation Certificate, together with a schedule of test results and a schedule of inspections.
The certificate includes space for three signatures - the person responsible for the design, the person responsible for the construction and the person carrying out the inspection and test of the installation.
It should be emphasized that the signature for the inspection and test section is the person who actually carries out the inspection and test and not someone else who may be in authority.
In some cases, all three sections may require signature by the same person and this is perfectly acceptable.
However, the Electrical Installation Certificate should not be signed until any defects identified by the person responsible for inspection and test have been corrected.
An Electrical Installation Certificate (or a Minor Electrical Installation Works Certificate), stating the extent of the works covered, shall be issued once the inspector is satisfied that the works comply with the regulations.
Any defects found in related parts of the installation, not affecting the safety of the alteration or addition should be reported in writing to the person ordering the work.
If existing defects affect the new work then these defects need to be corrected before an Electrical Installation Certificate can be issued and before the new work can be put into service.
An example of this is where bonding or equipotential bonding is inadequate or omitted, as this would seriously affect the safety of the whole installation, including the new work.
The Electrical Installation Certificate should not be used for periodic inspections.
The 17th Edition regulations stipulate that the designer of the installation is responsible for specifying the interval to the first periodic inspection and test.
There is also the positive recommendation (Regulation 135.1) that every electrical installation is subject to periodic inspection and testing by a competent person (in accordance with Chapter 62).
For example, the IEE Guidance Note for periodic fixed installation test frequencies advise a maximum period of five years between inspections and testing for commercial offices, shops and hospitals - reducing to three years for industrial facilities, leisure complexes and theatres.
For some special installations, such as swimming pools, petrol stations and caravan parks, the maximum period between inspections and testing is one year.
This represents a substantial difference from the previous edition, which presumed that a programme of risk assessments, records and preventative maintenance could be adopted in place of periodic testing.
The Periodic Inspection Report form is only to be used for the inspection of an existing installation and should include both inspection and test results.

 

[amberleaf]

Again the extent and limitations of the report needs to be stated and recommendations of defects and their remedies should be made.
The report includes a numbering system for this purpose, as follows: 1 - Requires Urgent Attention; 2 - Requires Improvements; 3 - Requires Further Investigation; and 4 - Does Not Comply With BS 7671:2008 (although this does not necessarily imply that the electrical installation is unsafe).
Several associations and trade bodies allow the issuing of a Minor Works Certificate.
A minor works is defined as 'work which does not include the provision of a new circuit'.
Testing is still essential and a number of tests are specifically identified as essential to confirm safety.
Also included on the form is space to allow the inspector to comment on the existing installation.
In a practical sense, for most electrical contractors involved in installation testing, the most frustrating part of the job is the recording of test data onto test certificates.
Invariably, current working practices involve the printing out or copying of a certificate for all premises to be tested at the beginning of the working day.
As circuit testing is undertaken on site the electrician will then usually record details of the inspection with written information on the 'dummy' certificate.
At the end of the day, back in the office, the manually recorded results will then be transferred to an 'original' certificate for the customer.

When Must The Tests Be Carried Out ? IEC ←← Our Cousins Over the Seas Regulations’ 2392-10 / 2391-10

The International Standard IEC-603664-6 Provides Requirements for “ Initial Verification “ and “ Periodic Verification “
Of an Electrical Installation :

“ Initial Verification “ Consists of Visual Inspection & Testing , of an Electrical Installation to Determine , as far as Reasonably Practicable , whether the Requirements’ of the Other Parts of IEC-60364 have been Met , Including Requirements for the Reporting of the Testing Results ,
The Initial Verification takes Place Upon Completion of a New Installation or Completion of Additions or of Alterations to Existing Installations ,

Periodic Verification : Provides the Frequency and the Requirements’ for Periodic Verification of an Electrical Installation to Determine ,
As far as Reasonably Practicable , Whether the Installation and all its Constituent Equipments are in a Satisfactory Condition for Use ,
Including Requirements for the Reporting of the Testing Results , Chapter 7 of this Guide Reports some Consideration of Periodic Inspection ,

This Guide will Not-Consider Visual Inspections ( for example the Checking of the Method of Protection Against the Electric Shock like Barriers
And Distances , Colour and Size of the Conductors , Presence of the Diagrams , Appropriate Selection of Materials , etc . )
But will Focus on the Various Testing Regimes and the Stipulated Values which these Tests should Deliver ,

Requirements For Testing An Electrical Installation :

The Following Tests shall be Carried Out where Relevant and should Preferably be Made in the Following Sequence :

* Continuity of the Protective Conductors and of the Main and Supplementary Equipotential Bonding Conductors :
* Insulation Résistance of the Electrical Installation :
* Protection by SELV & PELV or by Electrical Separation :
* Insulation Résistance of Non-Conducting Floors and Walls :
* Verification of Conditions for Protection by Automatic Disconnection of the Supply -
( Fault Loop Impedance , Earth Résistance , RCD Tests )
* Polarity and Phase Sequence Tests :
* Functional and Operational Tests :
* Voltage Drop :

The International Standard IEC-60364-6 Requires that all Measuring Instruments and Monitoring Equipment Used for the above Tests Comply with the Series IEC/EN 61557 , if Other Testing Equipment is Used , it shall Provide the Same Degree of Performance and Safety as a Minimum ,

Electrical Systems : “ Experiment “

An Electrical System Consists of a Single Source of Electrical Energy and an Installation ,
Depending on the Relationship between the Source and the Exposed ( Conductive ) Part of the Installation to Earthing ,
The Standards define the Type of System as Follows :

TT , System : the Accessible Conductive Parts are Earthed Indepently of the Source Earth :

TT : L1 ─────────────── ------- ────────────────────
……. L2 ─────────────── ------- ────────────────────
……. L3 ── * ──────────── ------- ───*──────────────── ( Single Phase )
…….. N ── * ──────────── ------- ───*──────────────── ( PE ) – ( R ) – Earthing

Earthing Rod ,

IT – System : the Live Parts are Insulated from the Earth ( or Connected to Earth Through an Impedance Z )
The Accessible Conductive Parts are Earth Independently :

……………………………………. 3-Phase
IT : L1 … . ────────────────── -------- ────────────────
……. L2 … . ────────────────── -------────────────────
……. L3 … * ────────────────── ------- ──*────────── L3 - ( Single Phase
…….. N * ─↓──────────────── ------- ─────*─────── ( PE ) – R ( Earthing
.. ……………..... Z
Earthing

IEC ←← Our Cousins Over the Seas Regulations’ 2392-10 / 2391-10

Insulation Résistance of the Electrical Installation :

The Insulation Résistance shall be Measured between each Live Conductor and the Protective Conductor or Earth ,
In Locations Exposed to Fire Hazards , a Measurement of the Insulation Résistance between the Live Conductors’ shall be Taken
The Insulation Résistance , Measured with the Test Voltage Values Indicated in the Table below are Satisfactory if each Circuit , with the Appliances Disconnected , has an Insulation Résistance Not-Less than the Appropriate Value given in the same table ,

Nominal Circuit ………………………….. Test Voltage …………………………… Insulation Résistance
Voltage ………………………………………. d.c. ………………………………….
────────────────────────────────────────────────────────────────
SELV , PELV ………………………………… 250 v ……………………………………… ≥ 0.5MΩ
( ≤ 50 v a.c. ≤ 120 v d.c. )
────────────────────────────────────────────────────────────────
Up to & including 500 v ……………………… 500 v ……………………………………... ≥ 1 MΩ
( including FELV )
────────────────────────────────────────────────────────────────
Above 500 v …………………………………… 1000 v …………………………………….≥ 1 MΩ
────────────────────────────────────────────────────────────────

Typically for 230 / 400 v Circuits ( Excluding SELV & PELV ) IEC 60364-6 Requires that the Insulation Résistance at a Test
Voltage of 500 v d.c. shall be 1MΩ as a Minimum :

NOTE: Where Surge Protective Devices ( SPDs ) are Likely to Influence the Test or be Damaged ,
Such Equipment shall be Disconnected before Carrying Out the Insulation Résistance Test , Where it is Not Reasonably Practicable to Disconnect such Equipment ( e.g. in Case of Fixed Sockets-Outlets Incorporating an ( SPD ) the test Voltage for the Particular Circuit may be Reduced to 250 v d.c. , but the Insulation Résistance must have a Value of at Least 1MΩ

Protection by SELV , PELV or by Electrical Separation : 2392-10 / 2391-10

Even if the Automatic Disconnection of Supply by Circuits-Breakers , Fuses and RCDs , is Normally the most Common Protection Method . there are Other Protection Methods like Protection by SELV , PELV or be Electrical Separation or by Non-Conducting Floors and Walls ,

Only for these Cases shall the Separation of Live Parts from those of Other Circuits , be Confirmed by a Measurement of the Insulation Résistance , The Résistance Values Obtained must be in Accordance with table :
Below there is an Example of the Measured of Insulation Résistance to Confirm the Separation of Live Parts from those of Other Circuits :

Test Instrument : (1) One Lead On ( Between the Output of the Transformer ) 2-Wires
Test Instrument : (2) One Lead On ( And the Other Live-Parts – for SELV / PELV )
( And the Equipotential Bonding Rads ( SELV Only )

Insulation Résistance of Non-Conducting Floors and Walls :

When it is Necessary to Comply with the Requirements of the Protection by Non-Conducting Locations , the Floor and Wall Insulation Résistance / Impedance shall be Tested
In Part 6 of IEC 60364 Methods for Measuring the Insulation Résistance / Impedance of Floors and Walls are given as Example ,

IEC ←← Our Cousins Over the Seas Regulations’ 2392-10 / 2391-10

Verification of Conditions for Protection by Automatic Disconnection of the Supply :

Automatic Disconnection of the Supply is Required where a Risk of Harmful Pathophysiological Effects to a Person may arise due to a Fault as a Result of the Value and Duration of the Touch Voltage ,
The Verification of the Efficacy of the Measures for Protection against Indirect Contact by Automatic Disconnection of Supply is Treated below :

In Case of TN-systems :

According to the International Standard IEC 603664 , for TN- system the Characteristics of the Protective Device and the Circuit Impedance shall fulfil the following Requirements :
( Zs x Ia ≤ Uo )
Zs : is the Fault Loop Impedance in Ohms ,
Uo is the Nominal Voltage between Phase to Earth ( Typically 230 V AC for Single Phase & Three Phase Circuits ,
Ia is the Current Causing the Automatic Disconnection of the Protective Device within the Maximum Disconnecting Times Required by IEC 60364-41 that are :

- 400 ms for Final Circuits Not Exceeding 32A ( at 230 / 400V ac )
- 5s for Distribution Circuits and Circuits Over 32A ( at 230V / 400V ac )

The Compliance with the above rules shall be Verified by :
(1) Measurement of the Fault Loop Impedance ( Zs ) by Loop Tester :
(2) Verification of the Characteristics and / or the Effectiveness of the Associated Protective Device , This Verification shall be Made :

 

[amberleaf]

- for Circuit-Breakers and Fuses , by Visual Inspection ( i.e. Short Time or Instantaneous Tripping Setting for Circuit-Breakers ,
Current Rating and Type for Fuses )
- for RCDs , by Visual Inspection and Test using RCD Testers Recommending that the Disconnecting times mentioned above are met ,

For Instance in a TN-system with nominal mains Voltage Uo = 230 V Protected by General Purpose gG fuses or MCBs ( Miniature Current Breakers ) required by IEC 898/ EN 60898 , the ( Ia ) and Max ( Zs ) Values could be :

Protection by ( gG fuses )
With Uo of 230 V
Rating ( A ) ……. Disconnection …………. Disconnection ( Regs BS – table 41.4
………………….. time 5s ………………….. tine 4s
……………….. Ia … Zs …………………. Ia … Zs ……
……………….. (A) .. (Ω) …………………(A) .. (Ω) …..
6 ……………… 17 ... 13.5 ……………….. 38 … 8.52 ….
10 ……………...31 ... 7.42 ……………….45 .. .5.11 ….
16 ……………...55 ... 4.18 ………………..85 … 2.7 ….
20 ……………...79 ... 2.91 ………………..130 …1.77 ….
25 ……………..100 ... 2.30 ……………….160 …1.44 ….
32 ……………..125 ... 1.84 ……………….221 …1.04 ….
40 ……………..170 ... 1.35 ………………. --- ….. ---
50 ……………..221 ... 1.04 ………………. --- ….. ---
63 ……………..280 ... 0.82 ………………. --- ….. ---
80 ……………..403 ... 0.57 ………………. --- ….. ---
100 ……………548 ... 0.42 ………………. --- ….. ---

The most Complete Loop Testers or Multifunction Testers also have the Prospective Fault Current Measurement , in this case Prospective Fault Current Measured with Instruments must be Higher than the Tabulated ( Ia ) of the Protective Device Concerned ,

Below is a Practical Example of Verification of the Protection by MCB in a TN-system ,
According to the International Standard IEC 60364 ,

Max Value of ( Zs ) for this Example is 1.44Ω ( MCB / 16A ) Characteristic C , THE Instrument reads 1.14Ω ( or 202A on Fault Current Range ) it means that the Condition ( Zs x Ia x ≤ Uo is Respected ,
In fact the ( Zs of 1,14Ω is Less than 1.44Ω ( or the Fault Current of 202A is more than ( Ia ) of 160A .
In Other words , in case of Fault between Phase & Earth , the Wall Socket Tested in this Example is Protected because the MCB will Trip within the Disconnection time Required ,

L3 -
N -
PE -

17th Edition - & -
Chapter 41 :
Protective Measure Against Electric Shock :

Under Some Sub-Cat ; ( Basic Protection ) ( Fault Protection ) ( Additional Protection )
Part-4 Protection for Safety

411.2 Requirements for Basic Protection :
411.3 Requirements for Fault Protection :
411.3.3 Additional Protection :

Now Designated ↔ Basic Protection , ( 410 ) ( i ) “ Insulation “ Applied to Live Parts “ Preventing Touching Live Conductors , Protection against Electric shock under fault-free conditions .

Note : for Low-Voltage Installations , systems and Equipment , Basic Protection generally corresponds to Protection against Direct Contact ,
That is “ Contact of Persons or Livestock with Live-Parts :

Now Designated ↔ Fault Protection ( 410 ) ( ii ) “ Protective Earthing “ Automatic Disconnection of Supply , ( ADS ) ←
Protection against Electric shock → Under Single-Fault Conditions ←

Note : for Low-Voltage Installations , systems and Equipment , Fault Protection generally corresponds to Protection against Indirect Contact ,
Is “ Contact of Persons or Livestock with → Exposed-Conductive-Parts which have become Live Under Fault Conditions ← :

415 : Additional Protection : Is Not Defined in Part 2 of the Regs , it is Detailed in Section ( 415 ) ←

Additional Protection against Electric shock can be Provided by Either !
( 415.2 ) Supplementary Equipotential Bonding ,
( 415.1 ) Additional Protection : Residual Current Devices ( RCDs ) Not Exceeding 30mA ↔ Operating time Not Exceeding 40mS

Protective Measures Against Electric Shock ,

* ( Basic and Fault Protection )
Extra Low-Voltage : SELV / PELV
SELV , is a Safety Isolation Transformer ( No Earth Provisions on the Secondary Side of the Transformer ) 230V- P │ ↔ │S- 12V a.c.
PELV , The Earth Provisions Continues through to the Load Side :

When it comes to Inspection there’s several things your got to check ? the First of those is does the Location your in which in this Location is the Bathroom has Requirements for SELV or PELV ,

Part 7 :Special Installation or Locations

You Need to Look up : P-169 / fig 701.2

( 701.55 ) In a Room Containing a Bath or Shower ; Suitable Fixed Current-Using Equipment , ( in Zone 0 , SELV / Remember Not PELV ,
Remember SELV is Located Outside the Zones ,
( iii ) SELV at a Nominal Voltage Not Exceeding 12V ac rms or 30V ripple-free d.c.

Zone O , Area Within the Bath or Shower : ▪▪▪
Zone 1 , Area Directly above Barth or Shower : ( Up to 2.25m Above the Finished Floor ▪▪▪
Zone 2 = Defined as Area Within 0.60m Circumference from the Bath or Shower : ▪▪▪

Regs : 17th , Socket-Outlet are Prohibited within a Distance of ( 3 m ) Horizontally from the Boundary of Zone 1 , This One will Come Up : p–167 ▪▪▪
Or ( FSU ) for Electric Towel Rail : ( RCD / Spur 30mA )

Arm’s Reach : N/A Accessibility in Zone O / Zone 1
N/A Electrical Equipment in Bathroom , ↔ 1 or more ( RCD 30mA “ Including Lighting Circuits “ ▪▪▪
( 701.512.2 ) IPX7 (i) Zone O / IPX4 , (ii) Zone 1 / 2 ( Lighting Bathroom ) ▪▪▪

( 702.522.24 ) Junction boxes : This One will Come Up : p–167 ▪▪▪▪
A Junction box shall Not be Installed in Zone 0 or 1 but in the case of SELV Circuits it is Permitted to Install Junction boxes in Zone 1

Termed an “ Extraneous Conductive Part “ Water Pipe , ( Not Part of an Electrical System / Equipment )

Functional Extra-Low Voltage ( FELV ) Exposed Conductive Parts of an FELV System are Connected to the Protective Conductor of the Primary Circuit of its Source : ( 411.7 )
Following shall be Used as Source of FELV , Transformer with Separations’ between Windings’ :

Heath and Safety 2392-10

The Electricity at Work Regulations 1989

12 Means for Cutting off the Supply and for Isolation ,
13 Precautions for work on Equipment made Dead ,
14 Work on or near live Conductors ,

12 Means for Cutting off the Supply and for Isolation

12.- (1) Subject to paragraph (3), where necessary to prevent danger , suitable means
( including , where appropriate , methods of identifying circuits ) shall be available for-
(a) cutting off the Supply of Electrical energy to any Electrical equipment ; and
(b) the isolation of any Electrical equipment .
(2) In paragraph (1),” isolation “ means the disconnection and separation of the
electrical equipment from every source of electrical energy in such a way that this
disconnection and separation is secure .
(3) Paragraph (1) shall not apply to electrical equipment which is itself a source of
electrical energy but, in such a case as is necessary , precautions shall be taken to prevent ,
so far as is reasonably practicable , danger .

Electrical Test Equipment for use by Electricians ( GS-38

Guidance on Safe Isolation Procedures for Low Voltage Installations :

Domestic : the Fundamental Principle of Safe Isolation Practice is that the Point of Isolation should always be under the Control of the Person who is carrying out the work at all Times : ( Locking Off )

For work on LV Electrical Equipment or Circuits , it is Important to Ensure that the Correct Point of Isolation is Identified ,
An Appropriate Means of Isolation is Used , and the Supply Cannot Inadvertently be Reinstated while the work is in Progress ,

Warning / Caution Notices should also be Applied at the Point(S) OFF Isolation , and the Conductors must be Proved to be Dead
At the Point of “ Work “ before they are Touched ,

Firstly you Must Guarantee the Point of Isolation is Correct , that the Circuit that your need to working on , making Sure that Correct Identification was Carried Out : ↔ “ Never Take for Granted “ ↔ the Circuit Chart or Identification of the Device :

( Isolation of Individual Circuits Protected by Circuit-Breakers )
Where Circuit-Breakers are Used , the Relevant Device should be Locked-Off Using an Appropriate Locking-Off Device
With a Padlock which can Only be Opened by a Unique Key or Combination , The Key or Combination should be Retained by the Person Carrying Out the Work .

The Principle is that Each Person carrying out such work should have Control of their own Point(s) of Isolation and Not Rely
On Others to Prevent Deliberate or Inadvertent Energization ,

( Typical Devices for Proving Dead ) “ Remember “ 2392-10 you’ll be Asked some of these Q/A “

The Procedure for Proving Dead should be by Use of a “ Proprietary Test Lamp or Two-Pole Voltage Detector as Recommended
In Guidance Note GS-38 ,
Electrical Test Equipment for Use by Electricians , Non-Contact Voltage Indicators ( Voltage Sticks ) and Multimeters should Not be Used ,

The Test Instrument should be Proved to be Working on a Known Live Source or “ Proprietary Proving Unit , before and after Use ,
All Conductors of the Circuit , Including the Neutral , should be Tested and Proved Dead :

 

[amberleaf]

Domestic Electrician : 2392-10

Note : in TT Systems , the Incoming Neutral Conductor Cannot Reliably be Regarded as being at “ Earth Potential :
This Means that for TT Supplies , a Multi- Pole Switching Device which Disconnects the Phase-Neutral Conductors
Must be Used as the Means of Isolation .

Note : in IT Systems , All Poles of the Supply Must be Disconnected , in these Circumstances , Single-Pole Isolation ,
Such as by Fuses or Single-Pole Circuit-Breakers , “ is Not Acceptable “

Temporary Disconnection of Incoming Supply :

For Some Type of Work on Existing Installations , such as the Replacement of Main Switchgear , Consumer Units etc .
It is necessary for the Distributors Service Fuse(s) to be withdrawn in order to Disconnect the Incoming Supply for
The Purpose of Isolation ,

Legally , Service Fuses can be Withdrawn Only by the Distributor , or by those they have Expressly Authorized to Carry Out such Work ,

Note : Some DBs are Manufactured with “ SLIDER SWITCHES “ to Disconnect the Circuit from the Live Side of the Circuit-Breaker
These Devices should “ NOT “ be Used as a Means of Isolation for Circuits , as they “ DO NOT “ meet The Requirements for Isolation
And the “ Wrong Switch “ Could Easily be Operated on Completion of the Work :

Domestic Electrician : 2392-10
Additional Precautions :

New Installations ,

New Installations can be a Particular Hazard as some of the Circuits or Equipment may require to be Modified after the
Installation has been Energized ,
It is therefore Important that every Protective Device is Correctly Identified at each Distribution Board before any Energizing takes place ,
And Safe Isolation Procedures , such as Locking-Off Circuit-Breakers as Particularly where a Number of Electricians are working on the same Installation ,

Alterations & Additions :

Alterations & Additions to Existing Installations can also be Particularly Hazardous , Records including Circuit Identification may not be Available ,
Or may be Inadequate or Incorrect , it is therefore Particularly Important to ensure that Circuits to be worked on has been Correctly Identified for Isolation Purposes ,

Neutral Conductors :

Care should be taken when working on Neutral Conductors of Circuits , The Practice of “ Borrowing Neutral , ( 314.4 ) i.e. making
Use of the Neutral of one of the Circuit for use on another Circuit , is Not Permitted by BS-7671 , this Dangerous Practice , however , may still be Encountered ,
Lighting & Control Circuits’ are the most Common Example : where this Practice is found , in these Circumstances , the Neutral
Conductor can become Live when the Conductor is Disconnected , if a Load is Connected to that Circuit ,
It is also Difficult to Identify Specific Neutral Conductor in “ Bunches “ of Single-Core Cables , such as where Enclosed in Trunking or Conduit ,
And care should be taken when severing such Cables that the correct Conductor has been Identified ,

Guide To Isolation Procedure : GS-38 / 2392-10 ( this will cover your Butt )

Pocket Size Guide ,

Step (1) : ( Locked Off )
Check it is Safe and Acceptable ( with the Occupier / User ) to Isolate, if the Isolator is an Off-Load Device ,
Remove the Load . Open the Means of Isolation for the Circuit(s) to be Isolated and Secure the Isolating Device in the Open Position with a
Lock or Other Suitable Means :

Step (2) : ( Proving Unit )
Prove the Correct Operation of a Suitable Voltage Detection Instrument , See Note (v) Guidance on Voltage Detection Instruments is given in
HSE Guidance Note GS-38 – Electrical Test Equipment for use by Electricians : against source ,

Step (3)
Using a Voltage Detection Instrument , Check that there is No Dangerous Voltage Present on any Circuit Conductor to be
Worked on , it is Important to Confirm that Conductors’ are Not Energized , Example ; due to a Wiring Fault , Check Terminal
Voltage between : (1) - ( Earth & Phase ) (2) – ( Neutral & Phase ) (3) – ( Earth & Neutral ) ,

Notes :
(a) in practice the equipment being worked on is likely to be remote from the consumer unit , example ,
A socket-outlet located remotely from the means of isolation , in this case it is necessary to check
that all the sockets-outlet contact terminals are “ Dead “
(b) when checking for a voltage between an earth terminal and live ( including neutral ) terminals ,
The test probe should make contact with the earth terminal first , to reduce the risk of the remaining
Probe becoming live ,

Step (4)
Prove the voltage detection instrument again against the known source to check that it was functioning correctly
When the circuit(s) were tested for the presence of voltage .

Notes :
(1) The Electricity at Work Regulations 1989 , require precautions to be taken against the risk of death or personal injury
from Electricity at Work activities Regulations ( 12 ) requires that , where necessary to prevent Danger : a suitable means is
available for cutting off the supply of Electrical Energy to any Electrical Equipment ,

Proving Dead Isolated Equipment or Circuits :

It is Important to ensure that the correct point of Isolation is Identified before Proving Dead ,
Following Isolation of Equipment or Circuits and before starting work it should be proved that the Parts to be worked on and those nearby , are Dead , it should never be Assumed that Equipment is Dead because a Particular Isolation Device has been Placed in the OFF Position ,

 

[amberleaf]

In the Case TT Systems : 2392-10 ( this will come up on the 17th Edition , -&- )

According to the International Standard IEC 60364 , for TT Systems the Characteristic’s of the Protective Device and the Circuit Resistance shall fulfil the following Requirements : ( Ra x Ia ≤ 50V )
Where :
( Ra ) is the Sum of the Resistance in Ω of the local Earth System and the Protective Conductor for the Exposed Conductive Parts ,
( 50 ) is the Maximum Safety Touch Voltage Limit ( It can be 25v in Particular Cases like Construction Sites , Agricultural Premises , etc . )
( Ia ) is the Current Causing the Automatic Disconnection of the Protective Device within the Maximum Disconnecting Times Required IEC 60364-41 :
-- 200mS for Final Circuits Not Exceeding 32A ( at 230 / 400 AC )
-- 1000mS for Distribution Circuits & Circuits over 32A ( at 230 / 400 AC )

The Compliance with the above rules shall be Verified by :
(1) Measurement of the Résistance ( Ra ) Regs : BS – 411.5.3. ↔ of the local Earth System by Loop Tester or Earth Tester .
(2) Verification of the Characteristics’ and / or the Effectiveness of the RCD Associated Protective Device ,

Generally in TT Systems , RCDs shall be Used as Protective Device and in this Case , ( Ia ) is Rated Residual Operating Current ( I∆n ) ,
For Instance in a TT System Protected by a RCD the Max ( Ra ) Values are :

Rated Residual Operating :
………Current ………………….. 30 ----- 100 ----- 300 ----- 500 ----- 1000 ----- mA
………. ( Ra )
( with touch voltage of 50V ) … 1667 ----- 500 ----- 167 ----- 100 ----- 50 ----- Ω
………. ( Ra )
( with touch voltage of 25V ) … 833 ----- 250 ----- 83 ----- 50 ----- 25 ----- Ω

Practical Example of Verification of the Protection by RCD in a TT System According to the International Standard IEC 60364 ,

The Standard Describes two methods for Testing the Résistance ( Ra )

- Volt-Ampere Method , Using Classical Earth Résistance Testers or the most Complete Multifunction Testers by sticking Two Auxiliary Earth Electrodes into the Ground . ( R – PE ) ( RCD 30 mA )

Fault Loop Impedance Method ( Loop Tester ) Regs BS- 6132.9 : the IEC 60364-6 Describes a Safe and easy Method to Test Earth Résistance
Where in a TT System , the Location of the Installation ( e.g. in Towns ) does Not Practice allow the two Auxiliary Earth Spikes to be Inserted into the Ground ,
This Method consists of the Measurement of the Fault Loop Impedance with a Loop Tester or a Multifunction Tester , in a TT Systems
Will in Practice give the Earth Résistance , ( RCD 30 mA )

For these Example the Max Permissible Value is 1667Ω ( RCD = 30mA and Contact Voltage Limit of 50V )
The Instruments’ Reads 12.74Ω : thus the Condition ( Ra ≤ 50 / Ia ) is Respected , However , considering that the RCD is Essential for Protection , it must be Tested as Follows :

Operation of Residual Current Devices ( RCDs ) in TT System :
Given that when the Protective Device is an RCD , ( Ia ) is Typically ( 5 ) times the rated Residual Operating Current ( I∆n ) then the RCD must be Tested Using RCD Testers or Multifunction Testers Recommending that the Disconnecting Times Required in IEC 60364-41 are Confirmed ,

The RCD Testers or Multifunction Testers can Perform the Tests for Single-Phase and Three-Phase RCDs by Measuring the Tripping Time , in TT System at 230 / 400V , the Tripping Time Measured by an RCD Tester or a Multifunction Tester shall be Lower than the Maximum Disconnecting Times as Defined by IEC 60364-41 that are :

- 200 mS for Final Circuits Not Exceeding 32A :
- 1000 mS for Distribution Circuits & Circuits Over 32A :

It is also Good Practice to Consider even more Stringent Trip Time Limits , by Following Standard Values of Trip Times at ( I∆n ) Defined by IEC 61009 ( EN 61009 ) and IEC 1008 ( EN 61008 ) These Trip Time Limits are listed in the Table Below :

Type of RCD …………………………………… Test at I∆n
General ( G) …………………………… 300mS Max . allowed value :
────────────────────────────────────────── ( Regs , BS – p-243 ,
General ( S ) …………………………… 500mS Max . allowed value :
………………………………………….. 130mS Min . allowed value :

Note : These Tripping Time Values are Applicable to RCDs Correctly Installed According to the Manufacturer Specifications :

( Old ) General Purpose RCDs to BS-4293 : Operating time less than 200mS : Remember ↔ ↔ ( BS- )
RCDs to BS-EN 61008 & BS-EN 61009 , Operating time below 300mS : Remember ↔ ↔ ( BS-EN )

Remember ↔ ↔ Note 2 Where ( Ra ) is Not known , it May be Replaced by ( Zs ) Regs : 411.5.3 )
411.5.3 ) (ii) Ra x I∆n ≤ 50V , ( Ze = Ra , electrode : Max permitted is 1666Ω , based on Not allowing the Voltage to Rise above ( 50V )

For IT Systems : IEC ←← Our Cousins Over the Seas Regulations’ 2392-10 / 2391-10

Compliance with the rules of IEC 60364-4-41 shall be Verified by Calculation or Measurement of the Current in case of a first Fault at the Line Conductor or at the Neutral :
Where similar conditions to TT or TN- Systems Occur , in the event of a second Fault in another Circuit , Verification is made as for TT or TN- systems as described above ,

Note : During the Measurement of the Fault Loop Impedance , it is necessary to establish a connection of negligible Impedance between Neutral Point of the System and the Protective Conductor Preferably at the Origin of the Installation or ,
Where this is Not Acceptable , at this Point of Measurement ,

Measurement of the Earth Electrode Résistance :
The International Standard IEC 60364-6 Provides Information Regarding the Measurement of the Résistance of an Earth Electrode for TT, TN and IT Systems , this Measurement shall be made by the Volt-Amperometric Method Using Two Auxiliary Earth Electrodes ,
The Instrument that covers , this Requirement is the Earth Tester : ( Measurement of the Earth Electrode Résistance )

( Earth Electrode , under Test ) 3 – Leads Used , 0ne on Earth Electrode
( Auxiliary Earth Electrodes , ) 0ne on each Aux Electrode ,

Note : The Auxiliary Earth Electrodes must be Placed at Sufficient Distance from the Earth Electrode Under Test in Order to
Avoid Overlapping of the Résistance Areas of the Electrodes ,

Polarity & Phase Sequence Tests :

Where the Standard Prohibits the Use of Single-Pole Switching Devices for the Neutral Conductor ,
A Test shall be made to Verify that all such Devices are Used Only for Line Conductor(s) ,
Where the Rules Require Double Pole-Switches , a Test shall be made to Verify that the Poles of such Devices are Connected
Correctly to the Appropriate Conductor ,

In the case of Multiphase Circuits it shall be Verified that the Phase Sequence is Maintained ,
In Particular a Test shall be made to Verify that the Devices ( i.e. Motors ) are Connected in the Correct Phase Sequence by a Phase Rotation Tester ,
Two Example : a Polarity Test Determine the Phase Conductor Using Digital Multimeter as a Voltmeter ,
( “ DEAD TEST “ Multimeter : One Lead on Phase Conductor / Other Lead on Earth Terminal : ( PE )
( Motor 3-Phase ) 3 – Leads , 1 / L1 , 1 / L2 , 1 / L3 , ( Remember Contacts are Open ,

Functional Tests :

Assemblies , such as Switchgear and Control gear Assemblies , Drives , Controls , and Interlocks , shall be Subjected to a Functional Test to Show that they are Properly Mounted , Adjusted and Installed in Accordance with the relevant Requirements of the IEC 603664 , Protective Devices shall be Submitted to Functional Tests , if Necessary , in Order to Check if they are Properly Installed and Adjusted ,

The fundamental rule of protection against electric shock, according to IEC 61140, is that
hazardous-live-parts must not be accessible and accessible conductive parts must not be
hazardous live, neither under normal conditions nor under single fault conditions.

 

[castlon11]

“ Rcd's “


Surface run cables do not require RCD protection. OSG p22

This statment conflict's with so many other regulations when taken out of context.

Other than this, very nice post, thanks

 

[amberleaf]

Additional Protection : ( Solar Photovoltaic ( PV ) Regs p-22

Solar Technology recommends always installing an RCD as additional protection in order to achieve the
highest possible degree of safety. It can also offer the function of an all-pole disconnecting switch, which is frequently required due to other reasons or regulations.
( South - 30º / 20V per-panel )
Remember Chaps : if your working on Mains ( 712.410.3 ) what the 17th is telling you is ? that if your working on ( PV )
After Isolation the ( DC ) is LIVE ←← ( This will come Up 17th -&- )
AC : day / Light On / Off , DC : Night Time Off / On
They will ask about the DC :side ( DC Side Class II ) WHEN Main Power is Isolated !! you will have to Isolate the DC Side as well ,
- Mains through an Isolation Switch ↔ ( a Must Warning Labels must be Placed ) ↔ Inverter > AC / DC , through an Isolation Switch on the DC Side ( if Used MCB ( B / Type )

( This will be Handy for , 17th Edition -&- )

Bath & Shower Rooms
All Electrical Equipment must be accessible for operation, Inspection & Testing , maintenance and repair. 132.12 :
Zone 0
Zone 0 for a bathroom is the area inside the bath. , 701.32.2
Zone 0 for a shower room is the area inside the shower basin. If there is no shower basin, zone 0 is 10cm high from the finished floor level and extends to 1.2m around the fixed shower head. 701.32.2
Electrical Equipment installed within zone 0 must be at least IPX7. 701.512.2
Only switches that are built into fixed Electrical Equipment and the insulated pull cords of pull cord switches are permitted in zone 0. No other switches or accessories are allowed. 701.512.3
Only SELV equipment not exceeding 12v ac or 30v dc is permitted in zone 0. The SELV equipment must be fixed and permanently connected with the transformer and isolator outside zones 0, 1 & 2. 701.55
Zone 1
Zone 1 for a bathroom is the same width as zone 0 (the width of the bath) extending to 2.25m above the finished floor level. 701.32.3
Zone 1 for as shower room is 2.25m from the finished floor level or the height of the fixed shower head from the finished floor level if more than 2.25m, and the width of the shower basin. If the shower has no basin then zone 1 extends to 1.2m around the fixed shower head. 701.32.3
If the space under the bath or shower basin is accessible without the use of a tool it is classed as zone 1, otherwise it is not considered to be a zone. 701.32.3
Zone 1 is separate from zone 0. 701.32.3
Electrical equipment installed within zone 1 must be at least IPX4 701.512.2
Only switches that are built into fixed electrical equipment, the insulated pull cords of pull cord switches and switches of SELV circuits not exceeding 12v ac or 30v dc are permitted in zone 1. The SELV transformer and isolator must be outside zones 0, 1 & 2. No other switches or accessories are allowed. 701.512.3
Showers & shower pumps, extractor fans , electric towel rails, whirlpool units, water heaters, lights and SELV or PELV equipment not exceeding 25v ac or 60v dc are permitted in zone 1. All equipment must be fixed and permanently connected , The SELV or PELV transformer and isolator must be outside zones 0, 1 & 2. 701.55
Zone 2
Zone 2 for a bathroom is the same height as zone 1 (2.25m) extended to 0.6m around the bath. 701.32.4
Zone 2 for a shower room is the same height as zone 1 extended to 0.6m around the shower basin. If there is no shower basin zone 2 is replaced by zone 1 extended to 1.2m around the fixed shower head. 701.32.4
Electrical equipment installed within zone 2 must be at least IPX4 excluding BS EN 61558-2-5 shaver supplies where direct spray from a shower will not occur. 701.512.2
Only switches that are built into fixed Electrical equipment the insulated pull cords of pull cord switches, BS EN 61558-2-5 shaver units and socket outlets and switches of SELV circuits not exceeding 12v ac or 30v dc are permitted in zone 2. The SELV transformer and isolator must be outside zones 0, 1 & 2. No other switches or accessories are allowed. 701.512.3
BS-7671 does not list permitted current using equipment for use in zone 2.
The extent of the zones in a bath or shower room can be limited by floors, ceilings and walls. For more detailed information see BS-7671 diagrams 701.1 & 701.2. Any electrical equipment installed on the surface of floors, ceilings and walls that limit a zone is subject to the requirements of that zone. 701.32.1
Electrical equipment that is exposed to water for cleaning must have a minimum degree of protection of IPX5 701.512.2

All circuits in a bath or shower room must be protected by a 30ma RCD. p6, 701.411.3.3 ,
Supplementary bonding is not required if all the extraneous conductive parts of the installation are connected to the main equipotential bonding. p-166 , 701.415.2
230v socket outlets are permitted 3m beyond the horizontal outside edge of zone 1. p-167, 701.415.3 ,
Circuits protected by electrical separation can only supply one item of equipment (excluding electric floor heating ) or one single socket. 701.413, 701.753
Electric floor heating must have a metal enclosure or sheath or a fine mesh metallic grid connected to the cpc of the supply circuit (SELV ) supplies excluded). 701.753
SELV and PELV enclosures in zones 0, 1 & 2 must be at least IPXXB or IP2X and the horizontal surface must be at least IPXXD or IP4X if accessible. Live parts must be covered by insulation that cannot be removed without force. If enclosures have to be opened for maintenance, the openings must be as small as possible with a warning that live parts can be touched. Unintentional touching of live parts must not be possible. 701.414.4.5
External influences , electrical equipment shall have at least the following degree of protection according to BS-EN 60529: (i) Zone O , IPX8 (ii) Zone 1 , IPX4 , IPX5 , where water jets are likely to occur for cleaning purposes , (iii) Zone 2 , IPX2 , for indoor locations , IPX4 for outdoor locations , IPX5 , where water jets are likely to occur for cleaning purposes , 702.512.2 .

Junction boxes , A junction box shall not be installed in zone O or 1 , but in the case of SELV circuits it is permitted to install junction boxes in Zone 1 , 702.522.24 ,

Sample Questions – 2392-10
Fundamental Inspection , Testing & Initial Verification – paper ( 4 )

1-A , 2-D , 3-C , 4-C , 5-C , 6-A , 7-A , 8-D , 9-B , 10-A , 11-B , 12-D , 13-C , 14-A , 15-B , 16-C , 17-D , 18-B ,
19-A , 20-D , 21-A , 22-D , 23-A , 24-C , 25-D , 26-B , 27-B , 28-B , 29-D , 30-D ,

Your Score should be 30 out of 30 :

Earth Electrode Résistance : GN-3 ( 2392-10 . Q/A some where a long the line some will come up , -&-

Measurement by Standard Method

( 612.7 ) When measuring earth electrode résistance to earth where low values are required ,
( 542.1 ) As in the earthing of the Neutral point of the transformer or generator , test method ( 1 )
( 542.2 ) below may be used ,

Instrument : Use an Earth Electrode Résistance Tester for this Test , Section 4.6

Earth Electrode Résistance Testers :
This may be a four-terminal instrument ( or a three-terminal one where a combined lead to the earth electrode would not have a significant Résistance compared with the Electrode Résistance ) so that the Résistance of the test leads and temporary spike
Résistance can be eliminated from the test results ,

Test method (1)
Before this test is undertaken , the Earthing Conductor to the Earth Electrode must be “ Disconnected “ either at the Electrode or ←← at the Main Earthing Terminal to ensure that all the Test Current Passes through the Earth Electrode Alone , ←←
This will leave the “ Installation Unprotected against Earth Faults “ , ←←

SWITCH OFF SUPPLY BEFORE DISCONNECTING THE EARTH : ←←←

( 542.2.2. ) The Test should be carried out when the ground conditions are least favourable , such as during dry weather ,

The test requires the use of two temporary test spikes ( Electrodes ) and is carried out in the following manner ,

Connection to the earth electrode is made using terminals C1 and P1 of a four terminal earth tester .
To exclude the résistance of the test leads from the résistance reading , individual leads should be taken from these terminals and connected separately to the electrode . if the test lead résistance is insignificant , the two-terminals may be short-circuited at the tester and connection made with a single test lead , the same being true if using a three-terminal tester . connection to the temporary spikes is made as

Test Instrument : temporary test electrodes 3-Test Leads , ( Green .C1 ↔ *─ Link out .P1 *─ ) ( Black . P2 *─ ) ( Red . C2 *─ )

AFTER COMPLETION OF THE TESTING ENSURE THAT THE EARTHING CONDUCTOR IS RECONNECTED : ←←←

 

[amberleaf]

TN-S System ( Single Phase ) Testing for ( Ze ) : What Could Happen !!!!!

One of the most Fundamental Differences’ between the Testing on a Initial Verification and a Periodic is that Testing for Initial Verification
Is to Certified that the Installation Complies with BS-7671

Where as a Periodic Report provides an Assessment of the Condition of the existing Installation , the reason for doing the ( Ze ) Testing now before Continuing with our Inspection , if there No Earth Facilities for this Installation then we have a Dangers Situation and we would have Severe Limitations on the other Tests , Continuing with the Tests would only prove Inaccurate
Readings and Only be Dangers to undertake ,

TN-S System ( Single Phase )
Supply : ↔ Source of Energy → │ → Installation

L , N , E ↔ Nil ↔ Exposed Conductive Parts :

Note: Each circuit may have more than one reason for additional protection by 30mA RCD e.g.: firstly because of the equipment i.e.: a socket outlet and secondly because of the cable installation method. Additional protection is provided as additional protection. It does not obviate
the need for circuit protection by circuit breakers or fuses.

Regulation 411.3.3 socket outlets with a rated current not exceeding 20A that are for general use by ordinary persons (exemption may be permitted).

* Regulation 701.411.3.3 Additional protection shall be provided for all circuits of the location by use of one or more 30mA RCD.
* Regulations 522.6.6 : 522.6.7 : 522.6.8 cables concealed in a wall or partition at less than 50mm depth and without earthed mechanical protection e.g. conduit.

* Regulation 314.1 Every installation shall be divided into circuits as necessary to avoid danger and inconvenience in the event of a fault, take account of danger that may arise from the failure of a single circuit such as a lighting circuit,
reduce the possibility of unwanted tripping of RCDs etc.


* Regulation 314.2 Separate circuits to be provided for parts of the installation that need to be separately controlled in such a way that those circuits are not affected by the failure of other circuits.

* Regulation 560.7.1 Chapter 56 circuits for safety services shall be independent of other circuits.
In addition Chapter 51 requires designers/installers to take account of all relevant British Standards and manufacturers instructions. For example BS5839

Part 6 is the British Standard for fire detection and alarm systems in dwellings. It states that power supplies to Grade D smoke alarms should be an independent circuit at the consumer unit, or a separately electrically protected local lighting circuit.

( With - 30mA RCDs Taking into account 3.14.1 : 3.14.2 : )

Domestic Inspection & Testing : ( 2392-10 , New Installation , Not been Energized yet )
Continuity of Radial Circuit Protective Conductors’ :
Dead Test ↔ GN-3 “ Test Prior to the Installation being Energized “

When you look at the Test Results Section on the Installation Certificate , “ Schedule of “ Schedule of Test Results “ : ( All Circuits . At Least One Circuit to be Completed ) You can see that Each of the Circuits is a Value of “ Big “ ↔ ( R1 + R2 ) Total Résistance of the Line & CPC Conductors or ( R2 ) just the Résistance of the CPC , is Required to be Recorded
( R2 ) ↔ is Generally Used for Periodic Inspection Reporting
You are Using the ( R1 + R2 ) Test Method : ←

They are a Number of Advantages to this Test Method , first we get the Information to Directly fill in the ( R1 + R2 ) Colum on the Test Schedule , ( 2 ) Polarity is Verified , and (3) the Method may be more Convenient than the Wander Lead method , and finally by Measuring the ( R1 + R2 ) for each Circuit we can Later Determine the Circuit Earth Loop Impedance ( Zs ) where Necessarily , so avoid the need to Perform Testing on Exposed Live Conductors , Example at Lighting Points

( 612.2.2 ) Continuity / Polarity :
(1) Here is a Cable Supplying the Upstairs Lighting Circuit , To do ( R1 + R2 ) Test , the Line & CPC Only , Together Into a Connector Block :

(2) Remember to Disconnect the Main Protective Bonding Conductor Effecting our Reading

You’ll have to go to Every Lighting Point on this Lighting Circuit and take a Continuity Reading : between the Line / CPC Conductors
With the Résistance off Test Results Null-Out ,

Your Going to take a Reading between the “ CPC “ and the “ Switch Line at the Ceiling Rose
Switch is “ ON “ Getting a Reading off ( 0.70Ω )

“ Polarity “ Can be Confirmed by Turning the Switch “ OFF “ ( you will get an Open Circuit if “ Polarity “ is Correct you have ( > 999.9 )
Don’t forget with a Two-Way and Intermediate Lighting Arrangement it will be necessary to repeat the “ Polarity “ by Operating all other Switches in turn
(3) One Lead on CPC - Insulated Crocodile Clip Green : ( the Furthest Part on the Circuit ) ← -&-
You’ll get the Highest Reading at this Point ( R1 + R2 ) -&- (4) Lead on Live / Switch Wire : Insulated Crocodile Clip , Brown
(5) Instrument on Test : you will be Recording on the Test Certificate : “ Schedule of Test Results “ Test Results ,
( All Circuits At Least One Column to be Completed ) ↔ ( R1 + R2 ) Box ↔ ( 0.8Ω )
You’ll now have to Remove the Connector Block back at the Consumer Unit : ( CCU ) for this Circuit ,
Don’t fall into the “ Trap “ off Carrying on with the Insulation Résistance Test for this Circuit because to Carry Out an
Insulation Résistance Test Correctly the Protective Bonding Conductors and all off the Circuit Protective Conductors will
Have to be Connected back Onto the Earthing Terminals , So it makes Sense to Carry on with the Continuity Tests On the Other Circuits
Before you do the Insulation Résistance Tests !!!!!!

“ Remember “ All the Main Protective Bonding Conductors Disconnected to Reduce the likely hood of Parallel Paths Effecting our Reading , -&-

“ Schedule of Test Results “

Remember : Ring-Final Circuits Only ( you only Use Little ( r1 ) Measured End to End Line , ← Loop . -&-
……………………………………….. ( you only Use Little ( r n ) Measured End to End , Neutral ← Loop . -&-
……………………………………….. ( you only Use Little ( r2 ) Measured End to End , CPC ← Loop . -&- ( End to End )


GN-3
Polarity :

The Polarity of all Circuits must be Verified before Connection to the Supply , with Either : GN-3 ( 612.6 ) -&-
An Ohmmeter or the Continuity Range of an Insulation and Continuity Tester :

Instrument : Use a Low-Résistance Ohmmeter for these Tests ,
( 612.2.1 ) The Instrument Used for low-Résistance Tests may be Either a Specialised low-Résistance Ohmmeter,
Or the Continuity Range of an Insulation and Continuity Tester , The Test Current may be d.c or a.c . it is Recommended that it be Derived from a Source with No-Load Voltage between 4V & 24V , and a Short-Circuit Current Not Less than 200mA ,

The Measuring Range should Cover the Span ( 0.2Ω to ( 2Ω ) with a Resolution of at least ( 0.01Ω ) for Digital Instruments ,

Instruments to BS-EN 61557-4 will meet the Above Requirements’ :

Ill be Shot for This !!! See you in Siberia “ I feel that Some Tutors do Not Teach the Right Things , Need to Know , my P45 ,
( Empty Barrels Make the Most Noise , )
( if you Make Everything Idiot Proof , Evolution will just Make a Better Idiot )
PS – is this Helping , you Chaps Out there , Amber

 

[amberleaf]

Schedule of Inspections : GN-3 2391-10 / 2392-10 ,

The Client ,
Certificates & Reports GN-3

( 631.1.) Following the Initial Verification of a New Installation or Changes to an Existing Installation ,
( 632.1.) an Electrical Installation Certificate , together with a Schedule of Inspections and a Schedule of Test Results ,
Is Required to be given to the Person Ordering the Work . in this context , “ Work “ means the Installation work ,
Not the work of carrying out the Inspection ( 631.2 ) and Test , likewise , following the Periodic Inspection and Testing of an Existing Installation ,
( 634.1 ) a Periodic Inspection Report , together with a Schedule of Inspections and a Schedule of Test Results , is Required to be given to the Person Ordering the Inspection ,

Sometimes the person Ordering the Work is Not the User , in such cases it is Necessary for the User ( e.g. Employer or Householder )
To have a Copy of the Inspection and Test Documentation . it is Recommended that those Providing Documentation to the Person Ordering the Work Recommend that the Forms be Passed to the User Including any Purchaser of a Domestic Property :

Electrical Installation Certificate : GN-3

Regulation ( 631.1 of BS-7671 Requires that, Upon Completion of the Verification of a New Installation ,
Or Changes to an Existing Installation , an Electrical Installation Certificate based on the Model given in Appendix 6 of BS 7671 , shall be Provided , Section ( 632 ) Requires that :
(1) the Electrical Installation Certificate be Accompanied by a Schedule of Inspections ( 632.1 )
And a Schedule of Test Results , These Schedules shall be based upon the models given in Appendix 6 of BS-7671 :
(2) the Schedule of Test Results shall Identify every Circuit , including its related protective ( 632.2 ) device(s) ,
And shall record the results of the Appropriate tests and measurements detailed in chapter 61 ,
(3) the Electrical Installation Certificate shall be compiled , signed / authenticated by ( 631.4 )
A competent person or persons stating that to the best of their knowledge and (632.3 )
Belief the Installation has been designed , constructed , Inspected and tested in accordance with BS-7671 , any permissible deviations being listed ,
(4) any defects or omissions revealed by the Inspector shall be made good and ( 632.4 ) Inspected and Tested again before the
Electrical Installation Certificate is issued :

Initial Inspection & Testing : GN-3

Forms 1 to 4 are designed for use when Inspecting and Testing a new Installation , or an Alteration or Addition to an existing Installation , The forms comprise the following :
(1) Short form of Electrical Installation Certificate ( to be used when one person is responsible for the design , construction , Inspection and Testing of an Installation )
(2) Electrical Installation Certificate ( Standard form from Appendix 6 of BS-7671 )
(3) Schedule of Inspections :
(4) Schedule of Test Results :

Notes : on completion and guidance for recipients are provided with the form ,

Periodic Inspection : GN-3

Form 6 , the Periodic Inspection Report from Appendix 6 of BS-7671 , is for use when carrying out routine Periodic Inspection
And Testing of an existing Installation , it is not for use when Alterations or Additions are made , a Schedule of Inspections and
Schedule of Test Results : should Accompany the Periodic Inspection Report :

Notes : on completion and guidance for recipients are provided with the form ,

Schedule of Test Results : GN-3 2391-10 / 2392-10 ,

The Client ,
Certificates & Reports GN-3
( 631.1.) Following the Initial Verification of a New Installation or Changes to an Existing Installation ,
( 632.1.) an Electrical Installation Certificate , together with a Schedule of Inspections and a Schedule of Test Results ,
Is Required to be given to the Person Ordering the Work . in this context , “ Work “ means the Installation work ,
Not the work of carrying out the Inspection ( 631.2 ) and Test , likewise , following the Periodic Inspection and Testing of an Existing Installation ,
( 634.1 ) a Periodic Inspection Report , together with a Schedule of Inspections and a Schedule of Test Results , is Required to be given to the Person Ordering the Inspection ,

Sometimes the person Ordering the Work is Not the User , in such cases it is Necessary for the User ( e.g. Employer or Householder )
To have a Copy of the Inspection and Test Documentation . it is Recommended that those Providing Documentation to the Person Ordering the Work Recommend that the Forms be Passed to the User Including any Purchaser of a Domestic Property :

Electrical Installation Certificate : GN-3

Regulation ( 631.1 of BS-7671 Requires that, Upon Completion of the Verification of a New Installation ,
Or Changes to an Existing Installation , an Electrical Installation Certificate based on the Model given in Appendix 6 of BS 7671 , shall be Provided , Section ( 632 ) Requires that :

(1) the Electrical Installation Certificate be Accompanied by a Schedule of Inspections ( 632.1 )
And a Schedule of Test Results , These Schedules shall be based upon the models given in Appendix 6 of BS-7671 :
(2) the Schedule of Test Results shall Identify every Circuit , including its related protective ( 632.2 ) device(s) ,
And shall record the results of the Appropriate tests and measurements detailed in chapter 61 ,
(3) the Electrical Installation Certificate shall be compiled , signed / authenticated by ( 631.4 )
A competent person or persons stating that to the best of their knowledge and (632.3 )
Belief the Installation has been designed , constructed , Inspected and tested in accordance with BS-7671 , any permissible deviations being listed ,
(4) any defects or omissions revealed by the Inspector shall be made good and ( 632.4 ) Inspected and Tested again before the
Electrical Installation Certificate is issued :

Initial Inspection & Testing : GN-3

Forms 1 to 4 are designed for use when Inspecting and Testing a new Installation , or an Alteration or Addition to an existing Installation , The forms comprise the following :
(1) Short form of Electrical Installation Certificate ( to be used when one person is responsible for the design , construction , Inspection and Testing of an Installation )
(2) Electrical Installation Certificate ( Standard form from Appendix 6 of BS-7671 )
(3) Schedule of Inspections :
(4) Schedule of Test Results :

Notes : on completion and guidance for recipients are provided with the form ,

Periodic Inspection : GN-3

Form 6 , the Periodic Inspection Report from Appendix 6 of BS-7671 , is for use when carrying out routine Periodic Inspection
And Testing of an existing Installation , it is not for use when Alterations or Additions are made , a Schedule of Inspections and
Schedule of Test Results : should Accompany the Periodic Inspection Report :

Notes : on completion and guidance for recipients are provided with the form ,

Requirements for Inspection & Testing : GN-3

General Procedure
( 134 ) Where Diagrams Charts or Tables are Not available , a Degree of Exploratory Work may
( 611.3 ( xvi ) be Necessary so that Inspection and Testing can be carried out safely and effectively. ( 514.9 ) A survey may be Necessary to indentify Switchgear , Controlgear and the Circuits they Control ,

Note : should be made of any known changes in environmental conditions , building structure , and alterations or additions
Which have affected the suitability of the wiring for its present load and method of installation ,

( 610.1 ) During the inspection , the opportunity should be taken to identify dangers which might
( 621.3 ) Arise during the testing , Any location and equipment for which safety precautions may be necessary should
Be noted and the appropriate step taken ,

Periodic tests should be made in such a way as to minimise disturbance of the installation and inconvenience to the user,
Where it is necessary to disconnect part or the whole of an installation in order to carry out a test , the disconnection should be
Made at a time agreed with the user and for the minimum period needed to carry out the test , Where more that one test necessitates a disconnection, where possible they should be made during one disconnection period ,

( 612.3.2 ) A careful check should be made of the type of equipment on site so that the necessary
( 612.3.3 ) precautions can be taken , where conditions require, to disconnect or Short-Out Electronic and other equipment
Which may be damaged by testing , Special care must be taken where control and protective devices contain electronic components ,

( 514.9 ) if the inspection ans testing cannot be carried out safely without diagrams or equivalent information , Section 6 of the Heath ans Safety at Work etc , Act 1974 can be interpreted to require their preparation .

 

[amberleaf]

16th / 17th

Edition Required local Supplementary Bonding be provided connecting together all exposed and extraneous conductive parts in the zones.
This is no longer required in this location provided the following conditions are met :
* All Final Circuits of the location comply with the Automatic Disconnection Requirements According to Regulation 411.3.2 :

* All Circuits are RCD protected in Accordance with 701.411.3.3

* All Extraneous-Conductive Parts of the location are Effectively Connected to the Protective Equipotential Bonding according to

regulation 411.3.1.2 ( Previously termed Main Equipotential Bonding :

-&- Ask you about Earthing / Protective Conductors , and all that look up Regs , p-32 ←←←←←←
16th Old Main Equipotential Bonding ↔ ( New 17th – Main Protective Bonding Conductor ) -&-
16th Old Supplementary Bonding ↔ ( New 17th – Supplementary Protective Bonding Conductor(s) where required : -&-

MINOR ELECTRICAL INSTALLATION WORS CERTIFICATE : GN-3 - 2392-10

Part 3 : Essential Tests :

The relevant Provisions of part 6 ( Inspection & Testing ) of BS -7671 must be applied in full to all Minor Works , for example , where a socket-outlet is added to an existing circuit it is necessary to :
(1) Establish that the earthing contact of the socket-outlet is connected to the main earthen terminal :
(2) Measure the insulation résistance of the circuit that has been added to , and establish that it complies with table 61 of BS-7671 ,
(3) Measure the Earth fault loop impedance to establish that the maximum permitted disconnection time is not exceeded :
(4) Check that the polarity of the socket-outlet is correct :
(5) ( if the work is protected by an RCD ) Verify the effectiveness of the RCD :

Part 1 : Description of Minor Works :

1 , 2 The Minor works must be so described that the work that is the subject of the certification can be readily identified :
(4) See Regulations ( 120.3 and 120.4 ) No departures are to be expected except in most unusual circumstances , also Regs , ( 633.1 )

Part 4 : Declaration :

1,3 The certificate shall be made out and signed by a competent person in respect of the design , construction , inspection and testing of the work :
1,3 The competent person will have a sound knowledge and experience relevant to the nature of the work undertaken and to the technical standards set down in BS-7671 , be fully versed in the inspection and testing procedures contained in the regulations and employ adequate testing equipment :
(2) When making out and signing a form on behalf of a company or other business entity, individuals shall state for whom they are acting .

Part 2 : Installation Details :
(2) The method of fault protection must be clearly indentified , e.g. Automatic Disconnection of Supply ( ADS )
(4) if the existing installation lacks either an effective means of earthing or adequate main equipotential bonding conductors,
This must be clearly stated see Regs , ( 633.2 )recorded departures from BS-7671 may constitute non-compliance with the Electricity Safety , Quality and Continuity Regulations 2002 ( as amended ) or the Electricity at Work Regulations 1989 , it is important that the client is advised immediately in writing ,

Isolation of Supply : GN-3

The Requirement of Regulation (14 ) of the Electricity at Work Regulations 1989 regarding working on or near live parts must be Observed during Inspection of an Installation ,

In Domestic type premises the whole Installation can be readily isolated for inspection ,
But with most other Installations it is Not-Practicable and too disruptive to isolate the whole Installation for the amount of time that is required for a comprehensive inspection , Much of the inspection in such premises has to be done whilst the Installation is in operation ,

Main switch panels can rarely be isolated from the supply for long periods; similarly, the disruption that may be caused by isolating final circuit distribution boards for long periods often cannot be tolerated ,

Distribution boards should be isolated separately for short periods for the internal inspection of live parts and examination of connections ,

Where it is necessary to inspect live parts inside equipment , the supply to the equipment must be disconnected ,

In order to minimise disruption to the operation of premises , the appropriate supplementary testing should be applied at the same time as the inspection ,

Accessories & Switchgear :
It is recommended that a random sample of accessories and switchgear is given a ( 611.3 ) (v)
Thorough internal visual inspection of accessible parts to assess their electrical and ( 611.3 ) (vi )
Mechanical condition , where the inspection reveals :

(1) results significantly different from results recorded previously
(2) results significantly different from results reasonably to be expected :
(3) adverse conditions , e.g. fluid ingress or worn or damaged mechanisms ,

The inspection should be extended to include every switching device associated with the installation under inspection unless there
Is clear evidence of how the damage occurred ,

Generally , it is not appropriate to apply sampling to socket-outlets and items of Class I equipment :

 

[amberleaf]

Direct Measurement of ( Zs ) :

Direct measurement of Earth-Fault Loop Impedance is Achieved by Using of an ( Earth-Fault Loop Impedance Tester )
( Instrument Designed Specifically for this Purpose ) Instrument Operates from the Mains and therefore can Only be Used on a Live Installation :

The Instrument is fitted with a Standard “ 13Amp Plug “ ( BS-1363 : Class I Equipment : BS-1362 : Cartridge Fuse : Regs: p-229 )
By Plugging the Instrument into a Suitable Socket-Outlet
Test Leads must Comply with GS-38 : Fused , 4mm / 2mm , for taking Measurement at other points on the Installation ,

In Order to Eliminate any Parallel Paths , 17th The Main Protective Bonding Conductors are Disconnected for the Duration of this Test ,
This will ensure that the reading is Not Distorted by the Presence of Gas or Water Service Pipes acting as part of the Earth return path ,
( Precautions Must be Taken , however , to Ensure that the Main Protective Bonding Conductors are Reconnected after Test ,

Earth-Fault Loop Impedance Testers are connected directly to the Circuit being tested and care must be taken to prevent danger ,
If a break had occurred anyway in the Protective conductor under test, then the whole of the earthing system could become live
It is essential therefore that Protective conductor continuity tests be carried Out Prior to the Testing of Earth-Fault Loop Impedance ,
( Communication with Other Users of the Building and the use of Warning Notices and barriers is essential ,

Measurement of ( Ze )

The value of ( Ze ) can be measured using an Earth Fault Loop Impedance Tester at the Origin of the Installation .
However , as this requires the removal of covers and exposure of live parts , Extreme care must be taken and the operation
must be supervised at all times, The Instrument is Connected Using Approved leads and probes between the Phase Terminal of the
supply and the means of Earthing with the Main switch Open or with all Sub-Circuits Isolated .
in order to remove the possibility of Parallel Paths, The means of Earthing must be Disconnected from Main Protective Bonding Conductors
for the Duration of the Test ,
with the Instrument correctly connected and the Test Button pressed , the Instrument will give a direct reading of the value of ( Ze )
Remember to Re-Connect all Earthing Connections on Completion of the test ,

Earth-Fault Loop Impedance :

When Designing an Installation , it is the Designers responsibility to ensure that , if a Phase-to-Earth Fault develop ,
The protection device will operate safely and within the time specified by BS-7671 :
Although the designer can calculate this in theory , it is not until the Installation is complete that the calculations can be checked ,

It is Necessary therefore to Determine the Earth-Fault Loop Impedance (Zs) at the Furthest Point in each Circuit and to Compare the Readings Obtained with Either the Designers Calculated Values or the Values Tabulated in BS-7671 :

The Earth Fault Loop is of the following Elements :

* The Phase Conductor from the Source of the Supply to the Point of the Fault :
* The Circuit Protective Conductor :
* The Main Earthing Terminal and Earthing Conductor :
* The Earth Return Path ( Dependent on the Nature of the Supply , TN-S , TN-C-S , etc :
* The Path through the Earthed Neutral of the Supply Transformer :
* The Secondary Winding of the Supply Transformer :

The Value of Earth-Fault Loop Impedance :
* Direct Measurement of ( Zs )
* Direct Measurement of ( Ze ) ( Ze ) at the Origin of the Circuit and Adding to this the value of ( R1 + R2 ) Measured during Continuity Tests , ( Zs = Ze + ( R1 + R2 )
* Obtaining the value of ( Ze ) from the Electricity Supplier and Adding to this the value of ( R1 + R2 ) as above ,
However , where the value of ( Ze ) is obtained from the Electricity Supplier and is not actually measured ,
A Test must be Carried out to Ensure that the Main Earthing Terminal is in Fact Connected to Earth Using an Earth Loop Impedance
Tester or an Approved Test Lamp :

Measurement by Standard Method : Method Using the Two ( Methods 1 / 2 ) 2392-10 / 2391-10 ,

The Test Requires the Use of Two-Temporary Test Spikes ( Electrodes )

E : = the Electrode in the Ground Under Test , ( C1 / P1 ) Link ,
C2 : = a Temporary Test Spike / Electrode ,
P2 : = a Temporary Test Spike / Electrode ,

> Test Method 2 : < GN-3 : ←←←←←

This is an Alternative Method : Earth Electrode for RCD ,
If the Electrode Under Test is being used in Conjunction with a Residual Current Device
The following Method of Test may be Applied as an Alternative to the Earth Electrode Résistance Test Described ,
In these Circumstances , Where the Electrical Résistances to Earth are relatively high and precision is Not-Required ,
An Earth Fault Loop Impedance Tester may be Used :

Earth Fault Loop Impedance Tester : GN-3 ←←←←←
These Instruments Operate by Circulating a Current from the Line Conductor into the Protective Earth ,
This will raise the potential of the protective Earth System ,

To Minimise Electric Shock Hazard from the potential of the protective conductor , the Test Duration should be within Safe Limits :
This means that the Instrument should Cut Off the Test Current after ( 40mS ) or a time Determined by the Safety Limits Derived
From the Information Contained within DD IEC/TS 60479-1 , if the Voltage Rise of the Protective Conductor Exceeds ( 50V ) during the Test ,

Test Method (1) 2392-10 : -&- I got this One , ←←←←← -&-
Before this Test is Undertaken , the Earthing Conductor to the Earth Electrode must be Disconnected Either at the Electrode or
At the Main Earthing Terminal , this will Ensure that all the Test Current Passes through the Earth Electrode Alone ,
However , as this will leave the Installation Unprotected against Earth Faults :

Switch Off the Supply Before ↔ Disconnecting the Earth , ←

 

[amberleaf]

Polarity : ( Competent Person ) ( Dead Test ) Apprentice : you'll get some Q/A on 17th Edition

Polarity tests are made to verify that every fuse or single-pole device is connected in the Phase Conductor Only , ( 612.6 )
> Edison screw lampholders should be connected so that the Phase conductor is connected to the Centre contact : <
Lampholders to BS-EN 60238 . in circuits having an earthed Neutral conductor , centre contact bayonet and Edison screw lampholders have the outer or screwed contacts connected to the Neutral conductor ( 612.6 (ii)


The Tests should be Carried Out before the Installation is Energised Using a Low-Reading Ohmmeter or Continuity Test Instrument ,
Much of the Polarity Testing can be Carried Out during the process of testing CPC continuity by using the ( R1 + R2 ) method .
However Polarity should also be confirmed after connection of Supply ,

Earth Fault Loop Impedance ( External to the Installation ) ( 612.9 ) ≈ ≈ ( Live Test ) ≈ ≈ ***
The external earth fault loop impedance ( Ze ) is one of the Supply characteristics to be recorded ( Ze ) can Only be measured by testing at the Origin of the Installation . “ Before Testing “ ( The Earthing Conductor must be Disconnected from
The Main Earthing Terminal and the Entire Installation must be Isolated from the Supply ,
The purpose of Disconnecting the Earthing conductor is to ensure that measurement is not affected by Parallel Paths of , for Example :
The Main Bonding Conductors . The Instrument to be Used is an Earth Fault Loop Impedance Test Instrument :

The procedure is as follows :
* open the main switch :
* disconnect the earthing conductor :
* check test instrument and leads :
* apply test probes to the live side of the main switch and disconnected earthing connection :
* check polarity indication for correct connection :
* press the test button and record results :
* reconnect the earthing conductor must be disconnected from the main earthing terminal and the entire installation must be isolated from the supply ,
The purpose of disconnecting the earthing conductor is to ensure that measurement is not affected by Parallel Paths of , for Example .
The Main Bonding Conductors . The instrument to be used is an Earth Fault Loop Impedance test instrument ,

The procedure is as follows :
* open the main switch :
* disconnect the earthing conductor :
* check test instrument and leads :
* apply test probes to the live side of the main switch and disconnected earthing conductor :
* check polarity indication for correct connection :
* press the test button and record result :
* reconnect the earthing conductor before restoring the Supply :

Circuit Impedance Measurement :
The type of instrument to be used is the same as that used for external impedance testing , The earth loop impedance ( Zs ) of every circuit should be measured at the point furthest from the incoming Supply ,
The test must be undertaken with all protective conductors connected :

Prospective Fault Current : ( 612.11 ) ≈ ≈ ( Live Test ) ≈ ≈ ***
This is the largest current that would flow in the event of a fault between live conductors or between a live conductor and the earthing conductor . the value should only be measured at the origin of the installation .
Only the largest value is recorded The earthing conductor , main bonding conductor and CPC should all be connected .
The instrument used is an earth fault loop impedance test instrument with a prospective fault current range ,

A Polarity Check should also be made on Incoming Supply : ( PS: I don’t know if you still get this at Collage ) ≈ ≈ Live Testing , ≈ ≈

Continuity of Protective Conductors . ( 612.2.1 ) GN-3 ( Dead Test )
Main & Supplementary Equipotential Bonding :

There are Two options for Undertaking this Continuity Test : ( R1 + R2 ) method (1) or wander lead ( R2 ) only method (2)

When testing for continuity of main and Supplementary Equipotential Bonding , it is usual to apply the ( R2 ) only test ,
Before carrying out this test to confirm continuity of the appropriate bonding conductor ,
It is necessary to avoid the measurement of parallel paths ,
Accordingly: it is advisable to disconnect one end of the bonding conductor to be tested and any intermediate connections with services .
The wander lead method is undertaken by connecting one lead of the test instrument to the main earthing terminal with a long lead ,
With this long lead and the other lead of the instrument , make connection at the remote end of the bonding conductor .
Remember to Null the test leads of their instrument for this test , otherwise the measured value will include the résistance of the wander lead ,
It is also important to remember to Re-Null the test leads of the instrument only when the ( R2 ) test is completed ,
Otherwise , again the measured value would give an incorrect measurement ,
The ( R1 + R2 ) method applies to circuit protective conductors and their associated phase conductor ,
The Procedure is as follows :
* Isolate the Supply :
* Connect the phase & cpc conductors together at the distribution board :
* Measure the résistance between phase and cpc at each outlet or point :
* Measure and record the résistance between phase & cpc at the furthest point :
* Remove the temporary phase / cpc connection :

The ( R1 + R2 ) method can also be used to check the polarity of each circuit .
When testing ( R1 + R2 ) at each point it is also necessary to operate the switch in order to confirm an open circuit condition
When the switch is in the off position , therefore confirming polarity ,

Continuity of Ring Final Circuit Conductors :
Requires five distinct steps to be undertaken . The confirmation of continuity of ring final circuits
( Unfortunately some contractors appear to omit steps 2 , 3 , 4 , ) the procedures are as follows :

Step 1 : ( Checking Continuity of Live and Protective Conductors of a Ring Final Circuit ) ↔ ( little r1 & r1 : r n & r n : cpc & cpc )
Conductor Continuity
Isolate the Supply ,
Measure the résistance of the End–to–End Phase , Neutral and Circuit Protective Conductors Separately And record the values ,
The values of the Phase & Neutral conductors will indicate whether or not the conductors are continuous ,
Moreover , the Phase & Neutral conductors should have the same value of résistance .
The results taken should be recorded as ( r1 , r n & r2 , ) Schedule of Test Results include the provision for recording
Such measurements , then a ( tick ) should be entered in the column marked Ring .

Step 2a : ( Ring Final Circuit with No Spur ) Lead on Line & Neutral / Lead on Line & Neutral :
Phase-to-Neutral :
Connect the incoming Neutral to the outgoing Phase of the circuit and vice versa , Measure the résistance between the pairs
And note the results , The reading obtained should be half that obtained for either the Phase or Neutral conductor in Step 1 :

Step 2b :
Measure between Phase & Neutral at each point on the Ring Circuit .The readings should be much the same as in step ( 2a )
Sockets wired as spurs will give a slightly higher reading , Schedule of Test Results include the provision for recording
Step 3 :
Phase-to-Earth :
Repeat steps 2a & 2b but using the Phase and CPC conductors , This test also confirms polarity , The highest value obtained should be recorded in the ( R1 + R2 ) column ,
Step 4 :
Reconnect the conductors :
Insulation résistance , Before proceeding with this Test it must be ensured that all equipment vulnerable to an insulation résistance test
Has been disconnected , The Insulation is normally measured between Live conductors and Live conductors to Earth
The procedure for insulation résistance testing between Live conductors is as follows :
* Isolate the Supply :
* Disconnect all current using equipment and close all switches :
* Disconnect equipment vulnerable to a test
* Check instrument and leads :
* Select test voltage range :
* Connect the instrument and record values of Phase to Neutral between Phases , and Phases to Neutral for ( 3 Phase-Supply ) and
Between Live conductors :

Step 3 : ( Ring Final Circuits with No Spur )
Step 4 : ( Ring Final Circuits with Unintentional Spurs )

 

[amberleaf]

“ Résistance and the Conductor “ 2392-10 : -&- you will be asked something like this Q/A

Résistance is directly proportional to length and inversely proportional to C.S.A. simply this means that More Length > More Résistance ,
and Less Length > Less Résistance , Also the Greater the C.S.A. the Less the Résistance , and the Smaller the C.S.A. the Greater the Résistance ,

"WHEN YOU GO TO WORK GUYS LOOK OUT FOR YOUR SELF AND YOUR PARTNER"

"PLAN ON STAYING ALIVE"

There are Proper Procedures that we all Should Follow when Working on Potentially Live Equipment. Testing Dead and Locking Off should be something that we do as a habit, and Remember to always Check your Tester on a Live Circuit before Using it to Test a Circuit Dead. Unfortunatly some Foremen and Contractors seem to forget that if One of Us gets Seriously Hurt or Killed in Order for them to get a Job Done Faster or Cheaper they are Liable and will be Prosecuted. Remember NOT Taking Chances is how “ Young Electricians get to be Old Electricians :

! Don't be a hero and stay alive !

Regulations : 12 / 13 / 14 / 16

Changes in the 17th Edition Jason can you move it to the right place Amberleaf

NOTE 1: This is not an exhaustive list.
NOTE 2: Particular attention is drawn to Section 701. This section now allows socket-outlets (other than SELV and shaver supply units to BS-EN 61558-2-5 ) to be installed in locations containing a bath or shower 3m horizontally beyond the boundary of zone 1.
• Regulation 131.6 – adds requirements to protect against voltage disturbances and implement measures against electromagnetic influences. In doing so, the design shall take into consideration the anticipated electromagnetic emissions, generated by the installation or the installed equipment, which shall be suitable for the current-using equipment used with, or connected to, the installation.
• Regulation 132.13 – requires that documentation for the electrical installation, including that required by Chapter 51, Part 6 and Part 7, is provided for every electrical installation.
• Chapter 35 – Safety services, recognizes the need for safety services as they are frequently regulated by statutory authorities whose requirements have to be observed, e.g. emergency escape lighting, fire alarm systems, installations for fire pumps, fire rescue service lifts, smoke and heat extraction equipment.
• Chapter 36 – Continuity of service, requires that an assessment be made for each circuit of any need for continuity of service considered necessary during the intended life of the installation.
• Chapter 41 – Protection against electric shock, now refers to basic protection, which is protection under normal conditions (previously referred to as protection against direct contact), and fault protection, which is protection under fault conditions (previously referred to as protection against indirect contact).
- Chapter 41 now includes those requirements previously given in Section 471 of BS 7671:2001.
- Chapter 41 now requires that for the protective measure of automatic disconnection of supply for an a.c. system, additional protection by means of an RCD with a rated residual operating current (IΔn) not exceeding 30 mA and an operating time not exceeding 40 ms at a residual current of 5 IΔn be provided for socket-outlets with a rated current not exceeding 20 A that are for use by ordinary persons and are intended for general use, and for mobile equipment with a current rating not exceeding 32 A for use outdoors. This additional protection is now to be provided in the event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users of the installation.
- Note that certain exceptions are permitted – refer to Regulation 411.3.3.
- Chapter 41 includes Tables: Table 41.2, Table 41.3 and Table 41.4 for earth fault loop impedances (replacing Tables Table 41B1, Table 41B2 and Table 41D). These new tables are based on a nominal voltage of 230 V (not 240 V), hence the values are slightly reduced. It has been clarified that where an RCBO is referred to in these Tables, the overcurrent characteristic of the device is being considered.
- Chapter 41 includes a new Table 41.5 giving maximum values of earth fault loop impedance for RCDs to BS EN 61008-1 and BS EN 61009-1.
- FELV is recognised as a protective measure and the new requirements are detailed in Regulation 411.7.
- Chapter 41 includes the UK reduced low voltage system. Requirements are given in Regulation 411.8.

• Chapter 42 - Protection against thermal effects, includes requirements in Section 422 Precautions where particular risks of fire exist (These requirements were previously stated in Section 482 of BS 7671:2001).
• Chapter 43 - Protection against overcurrent, includes those requirements previously given in Section 473 of BS 7671:2001. Information on the overcurrent protection of conductors in parallel is given in Appendix 10.
• Chapter 44 - Protection against voltage disturbances, includes a new Section 442, Protection of low voltage installations against temporary overvoltages due to earth faults in the high voltage system and due to faults in the low voltage system. This new section provides for the safety of the low voltage system under fault conditions including faults in the high voltage system, loss of the supply neutral in the low voltage system and short-circuit between a line conductor and neutral in the low voltage installation.
• Section 443 - Protection against overvoltages of atmospheric origin or due to switching, retains the existing text from BS 7671 and adds regulations enabling designers to use a risk assessment approach when designing installations which may be susceptible to overvoltages of atmospheric origin.
• Chapter 52 - Selection and erection of wiring systems, now includes busbar trunking systems and powertrack systems.
- It is now required to protect cables concealed in a wall or partition (at a depth of less than 50 mm) by a 30 mA RCD where the installation is not intended to be under the supervision of a skilled or instructed person, if the normal methods of protection including use of cables with an earthed metallic covering, mechanical protection (including use of cables with an earthed metallic covering, or mechanical protection) cannot be employed. This applies to a cable in a partition where the construction includes metallic parts other than fixings irrespective of the depth of the cable.
- Table 52.2 Cable surrounded by thermal insulation, gives slightly reduced derating factors, to take account of the availability of material with improved thermal insulation.
• Chapter 53 – Protection, isolation, switching, control and monitoring. Simplification means that requirements previously in Chapter 46, Sections 476 and 537 of BS 7671:2001 are now in this single chapter. Chapter 53 also includes a new Section 532 Devices for protection against the risk of fire, and a new Section 538 Monitoring devices.
• Chapter 54 - Earthing arrangements and protective conductors. The requirement that a metallic pipe of a water utility supply shall not be used as an earth electrode

 

[amberleaf]

is retained in Regulation 542.2.4 which also states that other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use. An example of other metallic water supply pipework could be a privately owned water supply network.
- A note to Regulation 543.4.1 states that in Great Britain, regulation 8(4) of the Electricity Safety, Quality and Continuity Regulations 2002 prohibits the use of PEN conductors in consumers’ installations. Regulation 543.7 has earthing requirements for the installation of equipment having high protective conductor currents, previously in Section 607 of BS 7671:2001.
• Chapter 55 - Other equipment, includes new additional requirements in Regulation 551.7 to ensure the safe connection of low voltage generating sets including small-scale embedded generators (SSEGs).
• Section 559 - Luminaires and lighting installations, is a new series of Regulations giving requirements for fixed lighting installations, outdoor lighting installations, extra-low voltage lighting installations, lighting for display stands and highway power supplies and street furniture (previously in Section 611 of BS 7671:2001).
• Chapter 56 - Safety services, has been expanded in line with IEC standardization.
• Part 6 - Inspection and testing, was Part 7 of BS 7671:2001. Changes have been made to the requirements for insulation resistance; when testing SELV and PELV circuits at 250 V, the minimum insulation resistance is raised to 0.5 MΩ; for systems up to and including 500 V, including FELV, the minimum insulation resistance is raised to 1.0 MΩ.
• Part 7 - Special installations or locations, was Part 6 of BS 7671:2001. The structure of Part 7 includes the following changes.
- Section 607 in BS 7671:2001 relating to high protective conductor currents has been incorporated into Chapter 54.
- Section 608 in BS 7671:2001 relating to caravans, motor caravans and caravan parks has been incorporated into
- Section 708: Electrical installations in caravan/camping parks and similar locations and Section 721: Electrical installations in caravans and motor caravans.
- Section 611 in BS 7671:2001 relating to highway power supplies is now incorporated into Section 559.
- The following major changes are incorporated in Part 7:
~~ Section 701 Locations containing a bath tub or shower basin.
~~ Zone 3 is no longer defined.
~~ Each circuit in the special location must have 30 mA RCD protection.
~~ Supplementary bonding is no longer required providing the installation has main bonding in accordance with Chapter 41.
~~ This section now allows socket-outlets (other than SELV and shaver supply units to BS EN 61558-2-5) to be installed in locations containing a bath or shower 3m horizontally beyond the boundary of zone 1.
• Section 702 - Swimming pools and other basins. This special location now includes basins of fountains. Zones A, B and C in BS 7671:2001 are replaced by zones 0, 1 and 2.
• Section 703 - Rooms and cabins containing sauna heaters. Zones A, B, C and D in BS 7671:2001 are replaced by zones 1, 2 and 3 (with changed dimensions).

• Section 704 - Construction and demolition site installations. The reduced disconnection times (0.2 s) and the 25 V equation no longer appear.
• Section 705 - Agricultural and horticultural premises. The reduced disconnection times (0.2 s) and the 25 V equation no longer appear. Additional requirements applicable to life support systems are included.
• Section 706 - Conducting locations with restricted movement, was Section 606 in BS 7671:2001.
• Section 708 - Electrical installations in caravan/camping parks and similar locations, now includes the requirement that each socket-outlet must be provided individually with overcurrent and RCD protection.
The following new sections are now included in Part 7:
• Section 709 - Marinas and similar locations
• Section 711 - Exhibitions, shows and stands
• Section 712 - Solar photovoltaic (pv) power supply systems
• Section 717 - Mobile or transportable units
• Section 721 - Electrical installations in caravans and motor caravans – previously in Section 608 of BS 7671:2001
• Section 740 - Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses
• Section 753 - Floor and ceiling heating systems.
Appropriate changes have been made to Appendices 1 to 7, in particular the methods and tables used in Appendix 4.

Earth Loop Impedance and Prospective Short Circuit (PSC) Testing Methods

Why Earth Fault Loop Impedance Test is Necessary ?

Earth fault loop impedance is the path followed by fault current when a low impedance fault occurs between the phase conductor and earth, i.e. "earth fault loop". Fault current is driven round the
loop by the supply voltage. The higher the impedance, the lower the fault current will be and the longer it will take for the circuit protection to operate.

To make sure the protection operates fast enough, the loop impedance must be low. Every circuit must be tested to make sure that the actual loop impedance does not exceed that specified for the protective device concerned. It is recommended that the (Ze) test be done first. This test, done at the distribution board, gives the loop impedance of the circuit, excluding the installation. The (Zs ) test, which includes the circuit tested in the (Ze) test as well as including the installation resistance, must be done next.

In most homes, basic shock protection is done by coordinating an earthing circuit with automatic switches in the indoor wiring circuits. This quickly cuts off supply to an earthing circuit where a fault occurs and touch voltage exceeds an acceptable limit. Proper protection against electric shock hazards is given when the TT wiring system complies with: Ra x Ia <50, where Ra is the sum of the resistances of earth bars and protective conductors and Ia is the maximum current of the protection system. Ra multiplied by Ia should not be more than 50 V, i.e. the maximum voltage one can touch will not exceed 50 V in the event of an earth fault.

Earth Fault Loop Impedance Testing :

The value of the earth fault loop impedance is the sum of transformer coil winding resistance, phase conductor (L1) resistance and the protective conductor (PE) resistance as well as the source earth resistance and installation resistance.
The Ze earth fault loop impedance measurement is made on the supply side of the distribution board and the main means of earthing, with the main switch open and all circuits isolated. The means of earthing will be isolated from the installation's earthing system (earth rods) bonding during the test. The Ze measurement will confirm the earth fault loop impedance as the sum of the resistances of the transformer coil winding, phase conductor or supply side and protective conductor resistance, but not the installation earth resistance

The Zs earth fault loop impedance should be tested at the furthest point of each circuit. In most cases the circuit breaker needs to be bridged out. The total earth fault loop impedance can be measured by plugging a loop tester into a socket outlet, or in some cases with an external earth probe. The value of the earth fault loop impedance is the sum of the resistances of the transformer coil winding , phase conductor (L1) and protective conductor (PE) as well as source earth and installation earth resistance.
When using an external earth probe, the earth fault loop impedance can be measured by touching an external probe directly to an earth bar, collector and connection point of an earth bar. The same measurement can be done by touching the earth probe to exposed, conductive parts of equipment in the circuits and exposed metal parts.

Prospective short circuit current (PSC) testing
The prospective short circuit or fault current at any point in an electrical installation is the current that would flow in the circuit if no circuit protection operated and a complete (very low impedance) short circuit occurred. The value of this fault current is determined by the supply voltage and the impedance of the path taken by the fault current. Measurement of PSC can be used to check that protective devices within the system will operate within safety limits and as per the safe design of the installation. ( PSC ) is normally measured between the Phase and Neutral at the DB or at a socket outlet.

 

[amberleaf]

2391-10 : Use the wording

Routine Electrical Inspection and Report-( sometimes known as Home buyers or sellers Report)

Electrical installations should not be left without any attention for the periods of years between formal periodic inspections. Also not everyone may require a formal periodic inspection; you may wish to choose a less comprehensive routine electrical inspection instead. Typically these are required in the years between periodic inspections to monitor for deterioration, or to assess condition before or after house purchase, or if you know the wiring to be relatively modern and did not require extensive testing.
The following is a list of what is covered in the inspection:

Visual inspection
o Main protective bonding bonding conductor
o Supplementary protective bonding conductor ( where required )
o Breakages or damage
o Wear or deterioration
o Overheating
o Missing parts
o Switchgear obstructions
o Security of enclosures
o Adequate labelling
o Loose fittings

Function test
o Switchgear
o Equipment switching
o Circuit breakers

Test
o RCD trip times
o Earthing (loop impedance) and Polarity of ring and radial socket circuits

Reports

On completion of the inspection a report will be provided, detailing the condition of the installation, results of tests carried out, any recommendations and conclusions as to the relative safety of the installation.

Cost- Domestic – Homes only


Domestic- Homes …………………………………………........ £ Please contact us for prices ,
Additional Consumer-Units ….. i.e. Garage … etc ………. £ Please contact us for prices ,

Please Note :
Prices shown are not subject to the addition of vat ,

Extent of the Work

When entering into an agreement for electrical inspection and testing of a building under your control it is a fundamental requirement that the extent and limitations of the inspection and testing are fully described. It is recommended that the following be agreed prior to beginning the work, and we can assist you in determining your exact requirements for inspection and testing.
As it is neither practical nor possible to inspect all parts of an installation, we will agree a sampling process. This is normally in the order of 10%-20% of all accessories, fittings and control equipment.

For much of the testing the electrical system will be switched off. If this is a problem we can arrange the work at times when this is more convenient.
We will agree before commencing the work the amount of down time that can be tolerated and arrange a provisional program for switching off – totally, and individual areas or distribution boards if required.
Reports

On completion of the Inspection and Test a report will be provided, detailing the condition of the installation, results of all tests carried out, a list of any faults, and recommendations and a conclusion as to relative safety of the installation.

Insulation Resistance of the Electrical Installation ( 612.3 )

The purpose of these tests is to verify that:
i. there are no short circuits between current carrying conductors or between live conductors and earth.
ii. There is no reduction in insulation resistance due to damage or dampness.
Test Instrument:
An insulation resistance tester having a DC test voltage which depends upon the supply voltage (Table 61 ) is required.

The polarity tests are necessary to verify that: ( 612.6 )

i. All fuses, single pole switches and protective devices are connected to the phase conductor only.
ii. The Centre Contract of Screw Type Lamp holders is Connected to the Phase Conductor with Outer or Screwed Contacts Connected to the Neutral Conductor,
iii. Wiring is Correctly Connected in Socket Outlets and Similar Accessories.

RCD tests ( Max test current for 100mA RCD is 100mA ) 2392-10 : this will come up ←←←← -&-

Testing Methodology :
Inspection &Testing and Certification

Electrical Installation Certificate
The Regulations require that an Electrical Installation Certificate in the form set out in Appendix 6 together with Schedule of Test
Results shall be given to the person ordering the work :

Regulation : ( 632.4 )
Requires any defect or Omissions revealed by Inspector shall be made good before an Electrical Installation Certificate is issued ,

Regulation : ( 631.4 ) ( 632.3 )
Requires : the Electrical Installation Certificate shall be signed by a competent person or persons staring that to the best of their
Knowledge and belief the Installation has be designed , constructed , inspected and tested in accordance with BS-7671 and permissible deviations being listed ,

Note 1 :
Requires : the Electrical Installation Certificate may Require Three Signatures :
Multiple Signature Electrical Installation Certificate,
(1) The Designer ,
(2) Person Constructing the job
(3) Inspection & Testing Engineer ,
Note 2 :
An individual may sign all three parts if he/she has designed , constructed , inspected & tested installation ,
Note 4 :
Certificates :
Single Signature Electrical Installation Certificate,
Where design ,construction ,inspection and testing are the responsibility of one person, a Certificate with a single signature may replace the multiple signature form ,
Note 5 :
Electrical Installation Certificate will accompany the following :
(1) Schedule of Inspections :
(2) Schedule of Test Results : ( p-334 )

The Sequence of Tests : GN-3 ,
Initial Tests should be Carried out in the Following Sequence ,

(i) Before the supply is connected , or with supply disconnected as appropriate

(1) Continuity of Protective conductors , including main & Supplementary Equipotential bonding : ( 612.2.1 )
(2) Continuity of Ring Final Circuit Conductors : ( 612.2.2 )
(3) Insulation Résistance : ( 612.3 )
(4) Polarity ( 612.6 ) by Continuity Methods :
(5) Earth Electrode Résistance : ( Using Earth Electrode Résistance tester )

Initial Tests should be Carried out in the Following Sequence ,
(ii) With the Electrical Supply Connected re-check Polarity Using an Approved Voltage Indicator before Further Testing ( GS-38 )
(1) Earth Electrode Résistance, Using an Earth Fault Loop Impedance Tester (2) Earth Fault Loop Impedance : ↔ ( 612.9 ) Phase / Neutral – Impedance ,
(3) Prospective Fault Current ( 612.11 ) Additional Loop , Higher for Line / Neutral Test ,
(4) Additional Protection : ( 612.10 ) ↔ Testing Residual Current Operated Devices
(5) Functional Test : ( 612.13 ) ↔ of Switchgear and Control Gear

Note : All Test Results should be Recorded on a , Schedule of Test Results complete with Inspection & Test Result Schedules of Inspections must be provided to the person ordering the work ,

Continuity of Protective Conductors :
Continuity of protective conductors including main and supplementary bonding ( 612.2.1 )

Every protective conductor, including the earthing conductor, main and supplementary bonding conductors, should be tested to verify that the conductors are electrically sound and correctly connected.

Test method 1 detailed below, as well as checking the continuity of the protective conductor, also measures ( R1+R2 ) which, when added to the external impedance ( Ze ) enables the earth-fault loop impedance ( Zs ) to be checked.

Note : (R1+ R2) is the sum of the resistance of the phase conductor R1 and the circuit protective conductor R2 :

Instrument - Use a low-reading ohmmeter :

The resistance readings obtained include the resistance of the test leads. The resistance of the test leads should be measured and deducted from all resistance readings obtained unless the instrument can auto-null. ( Subtract )
Test method 1
Connect the phase conductor to the protective conductor at the distribution board or consumer unit so as to include all the circuit. Then test between phase and earth terminals at each outlet in the circuit. The measurement at the
circuit's extremity should be recorded on the schedule of test results and is the value of (R1 + R2) for the circuit under test.
The test should be carried out before connecting any exposed-conductive-parts, which may provide parallel paths to the protective conductors.

 

[amberleaf]

Test method 2

Connect one terminal of the continuity tester to the installation main earthing terminal, and with a test lead from the other terminal make contact with the protective conductors at various points on the circuit, e.g. light fittings, switches, spur outlets etc. The resistance of the circuit protective conductors R2 is recorded on the test result schedule. Bonding conductor continuity can be checked using this test method. One end of the conductor and intermediate connections with services may need to be disconnected to avoid parallel paths.
Where ferrous enclosures have been used as the protective conductors, e.g. conduit, trunking, steel-wire armouring etc. the following procedure should be followed:

inspect the enclosure along its length for soundness of construction

perform the standard ohmmeter test using the appropriate test method described above.
Instrument - Use a low-reading ohmmeter for this test.

If the inspector feels that there may be grounds to question the soundness of this conductor, a further test may be performed using an a.c. ohmmeter which has a test voltage not exceeding 50 V and can provide a test current approaching 1.5 times the design current of the circuit excepting that it need not exceed 25 A.
Care needs to be taken when using high-current testers, as sparking can occur at a faulty joint. This test should not be carried out if this could be dangerous. Instrument - Use a high-current, low-impedance ohmmeter for this test.
( high current micro-ohmmeter suitable for measuring very low resistances )

TEST METHOD 1 - LINKING PHASE AND CPC :
Connect a temporary link between the phase conductor and the protective conductor at the distribution board. Using a low-reading ohmmeter test between the phase and earth terminals at each outlet in the circuit. The measurement obtained at the furthest point of the circuit should be recorded on the results schedule. This reading is the value of R1 + R2 for the circuit.

Note:
“ Main switch switched off “
Temporary link between Phase and CPC at the consumer unit. All fuses should be removed or MCB's switched off.

Remove temporary link when testing is complete.

TEST METHOD 2 - LONG LEAD METHOD

Connect one terminal of the ohmmeter to the earth terminal at the distribution board via a lead long enough to reach the furthest extremity of the circuit under test. The other terminal is then used to make contact with each outlet on the circuit.

Once resistance of the test leads is subtracted from the readings the corrected figure can be recorded.
Note:
All fuses out or MCB's switched off. Main switch switched off.

RING FINAL CONTINUITY TEST :
Purpose:

A test is required to verify the continuity of each conductor including the circuit protective conductor (CPC) of every ring final circuit.
The test results should establish that the ring is complete and has no interconnections.

Test Instrument required a Low Resistance Ohmmeter.

Step 1

Determine the resistance of each loop.

r1 - r2

r,n 1 – r,n 2

CPC1 - CPC2

Once the above readings have been established this will either confirm that the CSA of the CPC is the same as the phase conductor or smaller.

Step 2

Link-out Phase1 to Neutral 2 and Phase 2 to Neutral 1.
Now measure the resistance at every socket outlet between Phase and Neutral. The reading obtained should be the SAME at every socket outlet if the ring circuit has been connected up correctly.

The reading should be either ¼ of (Phase Loop + Neutral Loop) or ½ the reading of the Phase conductor loop.

Example

R1 - R2 = 1Ω

R,n 1 – R,n 2 = 1Ω

CPC1 - CPC2 = 1Ω

With Phase and Neutral cross linked, the reading at every socket outlet will be:

a) Phase loop 1 Ω + Neutral loop 1 Ω = 1 + 1 = 0.5 Ω
........................ 4 ............................ 4

b) Phase loop 1 Ω = 1 = 0.5 Ω ( 1÷ 2 = 0.5Ω )
....................2 ............. 2

Note: This reading is recorded on Test Certificate ,

Step 3

Remember

R1 = Resistance of Phase Conductor

R2 = Resistance of Circuit Protective Conductor

Now to measure R1 + R2 value of the ring final circuit.

Cross Link

Phase1 to CPC2

CPC1 to Phase2

Now measure the resistance at each socket outlet between Phase and CPC.

The reading at every socket outlet should be approximately the same.

Phase loop 1 Ω + Neutral loop 1 Ω = 1 + 1 = 0.5 Ω

....................4............................ 4 ( 1 +1 = 2 ÷ 4 = 0.5Ω


If one of the socket outlets is a spur, the reading here will be most likely the highest. It is this reading which needs to be recorded on the test result schedule under the column R1 + R2.

Note 1:
When carrying out this test you will automatically confirm the socket outlet, polarity, therefore there is no need to carry out a separate polarity test.
Note 2:
If the CPC cross sectional area is smaller e.g. 2.5/1.5, the resistance of the CPC will be 1.67 times higher than the phase resistance. Therefore, the readings measured at every socket outlet will differ slightly.

Note:

After connection of the supply, polarity should be confirmed using an approved voltage indicator (with leads conforming with HSE Guidance Note GS38).

Type of Inspection : 2392-10 most of them will come up Q/A ,

On demand Periodic Inspection and Test :
Periodic Inspection Report
Inspection Schedule & Schedule of Test Results

Documents :
Electricity at Work Regulations 1989
Health and Safety Executive Guidance Note GS38
BS7671 – Requirements for Electrical Installations

Personnel

First periodic test – designer / installer
Further periodic tests – Tester / Inspector
Extent & Limitations agreed with – person ordering the work

Instruments :
Continuity ring final circuit – low reading ohmmeter
Insulation resistance – insulation resistance tester
Live polarity – GS38 compliant voltmeter or test lamp.

Increase in Conductor Resistance :
Increase in ambient temperature
Increased circuit length - additions
Decreased conductor cross section – modifications

CPC Continuity :
At every Socket
Phase and CPC
Highest Value, therefore Circuit Value, for ( R1 + R2 )

Wiring systems not requiring separate CPC :
PVC-PVC insulated flat cable with CPC ( twin & earth )
MICC
SWA

Ring final circuit test :
P & N tested to ensure a valid ring circuit
If an interconnection existed

(i) CPC continuity, Figure-of-eight, (R1 + R2) measurement. Or
(ii) Polarity

Insulation Résistance, 600V Discharge lighting :
Insulation Résistance Tester
1000V d.c.
1.0 MΩ
Insulation Resistance 230V Installation :
500V
1.0 MΩ
2 MΩ
Polarity testing :
So that operating the device cuts line potential from the accessory protected.
Because live parts are only energised when lamp is in place.
To ensure supply is connected correctly at source.
Loop impedance :
Ze = External Loop Impedance
R2 = Resistance of circuit protective conductor
1.2 = Operating temperature correction factor. ( 1.2 is for bunched 70oC thermoplastic cables used at maximum operating temperature )
RCD tests : Loop impedance test determines that an earth fault loop path exists , Functional test determines that the RCD will actually operate in the event of a fault – electro-mechanical test using the ‘T’ button. , Max test current for 100mA RCD is 100mA

 

[amberleaf]

Scenario :
Testing :
* Periodic Inspection and Test, plus an Initial Inspection and Test, for the new part of the installation . * Periodic Inspection Report , Electrical Installation Certificate, plus Schedules of Test Results and Schedules of Inspections , * The person ordering the work gets the originals * First periodic test determined either by statute or by the designer * Statutory document = Electricity at Work Regulations 1989 * Non-statutory = BS7671, HSE Guidance Note 38

Human senses :
* Sight , * Smell , * Hearing ,
* Limitations of the inspection should be agreed with the person ordering the work , * BS3036 Fuses will not carry the large fault current. (They have a safe breaking capacity of either 1 or 4 kA) * PSCC between phases can be taken as twice the maximum measured value between any phase and neutral.
* Although the circuit is single phase, 230V, discharge lamps generate much higher voltages when striking. Should the insulation resistance tests, therefore, be carried out at 1000V, with a minimum acceptable value of 1 M ohm ? Personally, I’d say, no – we’re testing the wiring and switchgear, but it’s a debatable point.

What is GS38 ? ( Test Lead ) 2392-10

Guidance Note GS38, published by the Health and Safety Executive (HSE), sets out in clear and concise terms the features that any instruments and meters should have if they are to be used to carry out electrical tests in accordance with BS 7671. In order to comply with the Electricity at Work Regulations 1989 it is critical that any competent person carries out electrical testing safely, and this guidance note draws attention to the risks of using test instruments that do not meet the GS38 standard. In brief, some of the requirements for test instruments include:
• The test probes should have finger guards, ideally 4mm or 2mm of exposed conductive tip (to prevent the user accidentally making contact with either the probes or live conductors under test) and should be fitted with a High Breaking Capacity inline fuse or fuse-and-resistor combination with a low current rating (to prevent the probes rupturing under high short-circuit currents and/or damaging the test instrument if incorrect range settings are used, typically drawing more than 500mA).

• The test leads should be adequately insulated to suit the environment in which they’re being used, are coloured differently from each other so as to be distinguishable, are flexible, are capable of handling the maximum current range of the test instrument and are shrouded or sheathed to protect against mechanical damage, securely connect the leads to the test instrument and safeguard against the possibility of direct contact with live parts.

 

[amberleaf]

Question 1 :
State the necessary action that should betaken by an inspector on discovering a damaged socket outlet with exposed live parts
during a periodic inspection and test :
GN3 Page 14 - 1.2 ( Required Competence ) ( 634.2 )
(1) Make an immediate recommendation to the client to isolate the defective part :
Question 2 :
State the documentation that should accompany an Installation Certificate or Periodic Inspection Report ,
GN3 Page 14 - 1.3.1 ( Certificates and Reports ) ( 631.1 : 632.1 )
(1) Electrical Installation Certificate , together with a Schedule of Inspections
(2) and a Schedule of Test Results ,
Question 3 :
Why is it necessary to undertake an Initial Verification ?
GN3 Page 17 - 2.1 ( Initial Verification ) ( 610.1 : 611.2 : 612.1 )
(1) Confirm that installation complies with designers intentions ,
(2) Inspected and Tested Constructed, in accordance with BS 7671 ,
Question 4 :
State the requirements of Chapter 61 of BS 7671 with regard to initial verification ,
GN3 Page 17 - 2.1 ( Initial Verification ) ( 611.2 )
(1) All fixed equipment and material complies with applicable British Standards or acceptable equivalents ,
(2) All parts of the fixed installation are correctly selected and erected ,
(3) No part of the fixed Installation is visibly damaged or otherwise defective ,
Question 5 :
Identify four Non-Statutory documents that a person undertaking an inspection and test need to refer to ,
General Knowledge
BS 7671
IEE On-Site Guide
Guidance Note 3 Guidance Note : GS 38 , ( HSE )
Question 6 : Which non-statutory document recommends records of all maintenance including test results be kept throughout the life of an installation ? GN3 Page 17 - 2.1 (Initial Verification )( 631.1 )
The Memorandum of Guidance on The Electricity at Work Regulations 1989 ( HSR25 ) (EAWR Regulation 4(2)
Question 7 :
Appendix 6 of BS 7671 allows the use of three forms for the initial certification of a new installation or for an alteration or an addition to an existing installation. State the title given each of these certificates ,
GN3 Page 18 - 2.2 ( Initial Verification )
(1a) Multiple signature Electrical Installation Certificate ,
(2a) Single signature Electrical Installation Certificate ,
(3a) Minor Electrical Installation Works Certificate ,
(1b) The Multiple signature certificate allows different persons to sign for design , construction , inspection & testing,
And allows two signatories for design where there is mutual responsibility . where designers are responsible for identifiably separate parts of an installation , the use of separate forms would be appropriate .
(2b)where design , construction , inspection and testing are the responsibility of one person, a certificate with
A single signature may replace the multiple signature form ,
(3b)This Certificate is to be used only for minor works that do not include the provision of a new circuit ,
Such as an additional socket-outlet or lighting point ton an existing circuit ,
Electrical Installation Certificate , 2392-10 :
to be used when One person is responsible for the design Construction , inspection & testing of an Installation , p-332 ,
Approved Contractor issuing the Certificate has not been responsible for the design / or the inspection & testing of the
Electrical work ( p-333 certification of the three elements must be carried out separately using , ↔ the three sections headed ↔ Designer ( no 1 ) .. ↔ Designer ( no 2 ) .. first periodic (T)-(1) Designer / Installer , further periodic (T)-(2)
Tester / Inspecter , ( Construction (No 2) : Inspector ( Inspection / Testing ( No 3 )
Question 8 :
Under what circumstances would it be appropriate to issue a single signature Electrical Installation Certificate ?
GN3 Page 18 - 2.2 ( Certificates )
Where design, construction inspection and testing is the responsibility of one person ,
(2b)where design , construction , inspection and testing are the responsibility of one person, a certificate with
A single signature may replace the multiple signature form ,
Question 9 :
State the information that should be made available to the inspector ,
GN3 Page 18 - 2.3 ( Required information )
(1) Maximum demand , expressed in amperes , kW or kVA per Phase ( After diversity is taken into account )
(2) the Number and type of live conductors of the source(s)of energy and of the circuits used in the installation ,
(3)Type of earthing arrangements, used by the installation and any facilities provided by the distributor for the user ,
(4)the Nominal voltage(s) and its characteristics including harmonic distortion ( 313.1 ),
(5) the nature of the load current and supply frequency , (6) the prospective fault current at the origin of the installation , ( PFC ) (7)The Earth Fault Loop Impedance ( Ze ) of that part of the system external to the installation , (8) The suitability for the requirements of the installation, including the maximum demand , (9) Type and rating of overcurrent protective device acting at the origin ,of the installation ,
Note : These characteristics should also be available for safety services such as ( UPS ) and Generators ,

Question 6 : ops Which statutory document recommends records of all maintenance including test results be kept throughout the life of an installation ? GN3 Page 17 - 2.1 (Initial Verification )( 631.1 )
The Memorandum of Guidance on The Electricity at Work Regulations 1989 ( HSR25 ) (EAWR Regulation 4(2)

 

[amberleaf]

Inspection , Testing , Certification & Reporting :

Testing Continuity of Protective Conductor at a Lighting Switch by Wander Lead Method ,
Instrument : set on Ohms “ Continuity ↔ 20Ω ( Dead Test )

One Lead on Earthing Terminal at CCU / One Lead on the Earthing Screw on the Back-Box : you have Continuity = 0.41Ω

The Wander Lead Method , ( R2 )
This method is used principally for testing protective conductors that are connected to the main earthing terminal ( Main Equipotential bonding conductors , Circuit Protective Conductors and so on ) The correct Polarity of circuit connections will need to be Verified separately ,

Where a continuity test involves the opening of enclosures etc. that part of the installation will need to be isolated ,
One terminal of the continuity test instrument ids connected to the main earthing terminal with a long lead ( or “ wander Lead “ ) and ,
With a lead from the other terminal, contact is made with the protective conductor at every position to which it is connected in that circuit ,
Such as at socket-outlets, lighting points, fixed equipment points, switches, exposed-conductive-parts and extraneous- conductive-parts,
By this means, provided that no parallel paths are present, the continuity of the protective conductor back to the main earthing terminal can be verified , and its Résistance measured ,

A main or supplementary bonding conductor can be tested by simply attaching the leads of the test instrument to each end of the conductor, having temporarily disconnected one end of that conductor to remove parallel paths ,

Continuity testing of a Ferrous Enclosure using the wander lead method ,

Where a Ferrous Enclosure , such as Steel Conduit or Steel Trunking is used as a Circuit Protective Conductor,
The Integrity of the Enclosure should be verified for compliance with BS-7671, where reasonably practicable by Inspection & Testing

Inspection is to confirm the soundness of the enclosures conductive path , the inspector should indentify any deterioration such as excessive corrosion or the ability of any joints to provide durable Electrical Continuity and Adequate Mechanical Strength ,

Where Safe to do so, Testing of the Conduit or Trunking can be carried out by the Measurement of ( R1+ R2 ) or the Wander Lead method ,
Although these are ( Dead Tests ) both of these test procedures may require access to enclosures containing live parts ,
Therefore → ( Safe Isolation Must be Carried Out ) ← prior to gaining access , to prevent contact with any live parts ,
→ ( Before carrying out the Continuity test, “ Check that “ :

* Access to the Equipment is Not-Restricted , and once the Consumer Unit Cover is Removed , “ Check that “ :
* The basic Protection inside the Consumer Unit meets or exceeds the Requirements of IP2X or IPXXB , and
* The Terminal Insulated covers are unlikely to be Accidentally Displaced during Testing ,

The Wander Lead Method for Obtaining ( R2 ) values has been Described ,

Instrument : set on Ohms “ Continuity ↔ 20Ω ( Dead Test )

One Lead on the Earthing Screw on the Metal Back-Box : you have Continuity = 0.41Ω
The Other Lead on the Earthing Screw on the Metal Back-Box : ( your working on box –to-box : back to CCU Earthing Terminal , ( R2 )

( R1 + R2 )

For a simple circuit R1 + R2 is the phase conductor + the CPC impedance values and will be in ohms subtract from this any value for the leads that were obtained on the instrument check. The neutral should have the same csa of the phase conductor and should be almost equal to that of the phase impedance depending upon the circuit arrangement. For a three phase circuit the highest impedance is the one that could prevent a protective device operating thus this is the one used in practice against the chart to determine whether or not the reading is low enough and therefore recorded. Polarity can be checked at this point by making sure that single pole switches break the phase conductor and not the neutral or CPC.
Once continuity of all possible circuit combinations have been recorded I would guess that each circuit is tested for insulation resistance using the 500V range of an insulation tester for domestic premises. Although the leads should be shorted together to verify the meter reads zero, I prefer to place one lead on an earth and then verify my contact by connecting the other lead to another earth location close by. Since all wiring would need to be tested it is important to have all the switches are turned on. Where there is two lighting circuits this means that all combinations of the switching needs to be verified. I doubt the exam would go beyond the simple two way circuit.
A reading of zero Megohms could indicate that a shorting wire is still in place or that there is a fault. If a low test is obtained between phase and neutral it could be that a neon is used on a fused spur or that a genuine fault is present.

If tests revealed a fault and I resolved the problem then I would begin the tests again in case during my investigations I had inadvertently disturbed the wiring.

Electrical Inspection Testing & Certification : ( Dead Tests ) df

Electrical Installation Certificate
The Regulations require that an Electrical Installation Certificate in the form set out in Appendix 6 of BS7671 together with a schedule of test results shall be given to the person ordering the work.

Regulation ( 632.4 )
Requires any defect or omissions revealed by the inspector shall be made good before an Electrical Installation Certificate is issued.

Regulation ( 631.4 )
Requires: the Electrical Installation Certificate shall be signed by a competent person or persons stating that to the best of their knowledge and belief the installation has been designed, constructed, inspected and tested in accordance with BS7671 and permissible deviations being listed.

Note 1:
An Electrical Installation Certificate may require three signatures :
(1) The designer :
(2) Person Constructing the Job :
(3) Inspection and Testing engineer.
Note 2:
An individual may sign all three parts if he/she has designed, constructed, inspected and tested the installation.
Note 3:
The Electrical Installation Certificate will accompany the following :
(1) Schedule of Inspections : 2391-10 ↔ Use the Right Wording ← on your Exam
(2) Schedule of Test Result : 2391-10 ↔ Testing Checklist ( 611.3 ) ←←←
“ Test Result Schedule “ “ Inspection Schedule “

The Sequence of Tests :

Initial tests should be carried out in the following sequence:
Before the supply is connected, or with supply disconnected as appropriate
GN-3 ( 612.2.1 ) continuity of protective conductors, including main and supplementary bonding
GN-3 ( 612.2.2 ) continuity of ring final circuit conductors ( R1 + R2 )
GN-3 ( 612.3 ) insulation resistance ( “ High Résistance Using d.c. Voltage )
GN-3 ( 612.6 ) polarity ( by continuity methods )
GN-3 ( 612.7 ) earth electrode resistance, using earth electrode resistance tester ( Method 1 )

With the electrical supply connected re-check polarity using an approved voltage indicator before further testing : ≈ ≈ ≈ ≈

GN-3 ( 612.9 ) earth electrode resistance, using an earth fault loop impedance tester ( Method 2 )
GN-3 ( 612.9 ) earth fault loop impedance : ( Phase / Neutral = Impedance ) where protective measures are used which require a knowledge of ( earth fault loop impedance ) the relevant impedances shall be measured ,or determined by an alternative method , Zs = Ze ( R1 + R2 ) :
Note : further information on measurement of earth fault loop impedance can be found in appendix 14 / p-361
Zs (m) ≤ 0.8 x Uo ÷ Ia : ( 230 ÷ 24A = 9.58 , ( Ze / 0.8 x Zs 9.58 = 7.66
From the City & Guild Chief examiners reports it appears that many get calculations of ( Zs ) ( Ze ) R1 and R2 wrong.
( Zs ) is the sum of ( Ze ) R1 and R2 seems simple enough. Zs = Ze + ( R1+R2 ).
( Ze ) is the external impedance. Although you can calculate the value, it is more normal that the value is obtained by measurement using a suitable instrument or by enquiry.
R1 is the resistance of the phase conductor :
R2 is the resistance of the CPC or circuit protective conductor. :
In practical test situations the value of R1 + R2 is obtained in one test so could in effect be considered as one value say Rt. So the equation would become Zs = Ze + Rt.
So why Z and R ? :
Z is the impedance and applies to AC circuits :
R is resistance and applies to DC circuits :
GN-3 ( 612.11 ) prospective fault current ( Live / Neutral )
GN-3 ( 612.10 ) residual current operated devices ( BS – Only - 200mS ( BS-EN – 300mS :
GN-3 ( 612.13 ) functional test ( Light Switches , switchgear and control gear
Note:
All test results should be recorded on a schedule of Test Results form
Report Forms complete with Schedules of Inspection and Schedules Test Result must be provided to the person ordering the work.

 

[amberleaf]

TT , TN-C-S , IT , TN-C Earthing Arrangements :
In Latin earth is called Terra (Terre in French ) so we get Terra Firma, on solid ground.

So the first letter denotes if the supply is connected to Earth or Terra with the capital letter T. If insulated from earth then I is used, I for insulated.

The second letter denotes where the consumers earth is connected to. So T would indicate to earth. So TT means that the supply transformer star point is connected to earth and the consumers equipment is also connected to earth using earth spikes etc.

In an IT system the supply transformer has no connection to earth but the consumers equipment is connected to earth using earthing spikes etc.

N stands for neutral and thus in a TN system the consumers earth is connected to earth via the neutral of the supply.
TN S is where the earth and neutral are fed back to the supplier with separate conductors.
TN C is where the earth and neutral are fed back to the supplier using one conductor. ( PEN )
TN-C-S is where the earth and neutral are fed back to the supplier using one conductor but this time the connection of the earth to the neutral is not directly made at the consumers end thus there are two separate conductors from the premises.

Testing – ( the live tests )
612.8 - Protection by automatic disconnection of supply
612.9 - Earth fault loop impedance
612.10 - Additional protection ( RCDs )
612.11 - Prospective fault current
612.12 - Check of phase sequence
612.13 - Functional testing ( inc. RCDs )
612.14 - Verification of voltage drop
Testing – ( the dead tests ) GN-3
612.2 - continuity of protective conductor’s including main and equipotential bonding
612.2.2 - Continuity of ring final circuits
612.3 - insulation resistance (see table 61)
612.4 - protection by SELV, PELV or protection by separation
612.5 - Insulation resistance of floors and walls
612.6 - Polarity
612.7 – Earth electrode resistance
Testing – ( the dead tests ) GN-3
Table 61 – Minimum Values of Insulation Resistance
Note: some of these values have changed from the previous edition
≥ 1.0 1000 Above 500V ≥ 1.0 500 Up to and including 500V with the exception of the above system ≥ 0.5 250 SELV and PELV Minimum insulation resistance ( M Ω ) Test voltage d.c. ( V ) Circuit nominal voltage ( V )

The correct documentation must be issued to the person ordering the work TYPE OF WORK COMPLETED TYPE OF FORM REQUIRED New installation or change to existing installation Electrical Installation Certificate New installation work that does not include the provision of a new circuit Electrical Installation Certificate or Minor Electrical Installation Works Certificate Alterations or additions Electrical Installation Certificate Alterations or additions that does not include the provision of a new circuit Electrical Installation Certificate or Minor Electrical Installation Works Certificate Periodic Inspection and Testing Periodic Inspection Report

* Electrical Installation Certificate : This form to be used when only one person is responsible for the design, construction and testing of the installation * Electrical Installation Certificate : This requires 3 signatures ( The designer , The constructer , The inspector )
You will need to complete one of these for every installation that has been tested.
The Installation Test Certificate : Minor Works Certificate To be used for minor works only, Not for new circuits, or New installations

Periodic Inspection Report : To be used when “next inspection” date is due – or On change of use - or On change of ownership This is now part of the “sellers pack” when homes are for sale
SPECIAL INSTALLATIONS OR LOCATONS ;
COMPETANT PERSON , From Part 2 Definitions , A person who possesses sufficient technical knowledge, relevant practical skills and experience for the nature of the electrical work undertaken and is at all times able to prevent danger and, when appropriate, injury to himself/herself and others.
Check of phase sequence For multi-phase circuits there is a requirement to verify that phase sequence is maintained
Verification of voltage drop This subject matter was covered previously in Section 523 ( and Appendix 12 ). Regulation 612.14 is short , so briefly familiarize yourself with its content.
Part 6 Inspecting and Testing :
Limited changes in Part 6 with model certificates & reports remaining largely unchanged
Insulation values increased - For systems up to and including 500 V the minimum insulation resistance is now 1MΩ
More detailed requirements are provided in relation to RCD testing
New regulations are included in relation to the checking of phase sequence and verification of voltage drops
Section 610 – General : 610.1

Every installation shall, during its erection and on completion before being put into service, be inspected and tested to verify, as far as is reasonably practicable, that the requirements of the regulations have been met.
Precautions shall be taken to avoid danger to persons and to avoid damage to property and installed equipment.
Section 610 – General
610.2 – See sections 131, 311 to 313 and 514.9.1 for information required for the fundamental principles.
610.3 – The verification shall include comparison of the results with the relevant criteria to confirm that the requirements of the “Regs” have been met.
610.4 – For an addition or alteration to an existing installation. It shall be verified that the addition or alteration complies with the regulations, and does not impair the safety of the existing installation.
Section 610 – General (cont.)
610.5 – The verification shall be made by a competent person .
610.6 – On completion of the verification, according to regulations 610.1 to 610.5, a certificate or certificates, shall be prepared.
Section 611 – Inspection
611.1 – The inspection shall precede testing and shall normally done with that part of the installation under inspection disconnected from the supply.
Section 611 – Inspection (cont)
611.2 – The inspection shall be made to verify that the installed electrical equipment is:-

1.
In compliance with section 511 (this may be ascertained by mark or by certification furnished by the installer or by the manufacturer), and
Correctly selected and erected in accordance with the regulations, and
Not visibly damaged or defective, so as to impair safety.
Section 611 – Inspection
611.3 – the inspection shall include at least the checking of the items on the inspection check list, where relevant to the installation, and where necessary, during erection:
A complete inspection checklist is shown in appendix 6 and also available to download from Forms for electrical contractors - The IET as indeed, are all of the forms that you may require.
2.
Section 611 – Inspection
The Schedule of Inspection
This form will be used for ALL installations
Record all your observations here with either a tick ( ) a cross ( x )or ( N/A ) or ( Lim ) p- 340 / regs
Simply work your way through the form item by item, this will ensure compliance with regulation 611.3.
612 - Testing
The tests of regulation 612.2 to 612.13, where relevant, shall be carried out and the results compared with the relevant criteria.
The tests of regulation 612.2 to 612.6, where relevant shall be carried out in that order before the installation is energized .
Where the installation incorporates an earth electrode, the test of regulation 612.7 shall also be carried out before the installation is energized
612 – Testing
If any test indicates a failure to comply, that test, and any preceding tests, the results of which may have been influenced by the fault indicated, shall be repeated after the fault has been rectified.
Some methods of test are described in the IEE Guidance Note 3 ( when available ), Inspection and Testing, published by the Institute of Engineering and Technology.
Other methods are not precluded provided that they give valid results.
612 – Testing Section 612 details the required tests to be for initial verification. The tests should be carried out in a prescribed sequence, some prior to the circuits being energized.

( 314.1 ) dividing the installation into circuits so as to: -
Avoid danger and minimize inconvenience in the event of a fault
Facilitate safe testing, inspecting and maintenance
( 314.2 ) ( 314.3 ) ( 314.4 )

 

[amberleaf]

17th Edition requirements for testing of RCDs The 17th Edition has the following requirements in terms of verification of installed RCDs:

612.8.1 requires the effectiveness of automatic disconnection of supply by RCD to be verified using test equipment meeting the requirements of BS EN 61557-6 ( Electrical safety in low voltage distribution systems up to 1000 V a.c. and 1500 V d.c P-12 Regs ).
– Equipment for testing, measuring or monitoring of protective measures. Residual current devices (RCD) in TT, TN and IT systems). This is to confirm that the relevant requirements of Chapter 41 (Protection against electric shock) are met.

BS EN 61557-6 has requirements for the following tests to be applied to RCDs:
- Non-tripping (50%) test
- Tripping (100%) test
- 5 I∆n ) (500%) test

612.13.1 requires the effectiveness of the integral test facility of an RCD to be verified.
415.1.1 states that where an RCD having an I∆n of 30 mA or less is installed to provide additional protection, its operating time should not exceed 40 ms at a residual current of 5 I∆n .

Recommended test procedures
Although the following tests are not required by BS 7671: 2008 they are a method of establishing that the
device meets the requirements of Chapter 41. Remember, in order for reliable results to be obtained
when performing these tests, any loads should be disconnected from the circuits and/or outlets under test .

Non-tripping test.
The purpose of this test is to confirm that an RCD of any type or trip rating is not overly sensitive and is a measure
intended to enable unsuitable RCDs to be identified and removed from service. The continued presence of overly sensitive RCDs tends to reduce user confidence in such devices and may encourage the adoption of potentially dangerous practices such as the “bridging-out” of RCDs in order to avoid unwanted tripping.

Test procedure - With a leakage current equal to 50% of the rated residual operating current (I∆n ) ( applied, the RCD should not operate.
Tripping current test
The purpose of this test is to confirm that the residual operating current of the protective device is less than or equal to the rated
residual operating current. This is a measure of the continued effectiveness of the device to work as required by
BS 7671 and in accordance with its product specification when installed for the purpose of providing automatic
disconnection in the event of a fault. It does not demonstrate its suitability in terms of providing additional
protection. The test should be performed in both the positive and negative half-cycles.

Test procedure -

General purpose RCD to BS EN61008 and RCBO to BS EN 61009
With a leakage current flowing equivalent to 100% of the rated residual operating current (I∆n ) of the RCD, operation should occur within 300 mS.

“S” type RCD to BS EN 61008 ( incorporating an intentional time delay )
With a leakage current flowing equivalent to 100% of the rated residual operating current ( I∆n ) of the RCD, operation should occur
within a time range from 130 mS to 500 mS.

General purpose RCD to BS 4293 and RCD protected socket-outlets to BS 7288 With a leakage current flowing equivalent to 100% of the rated residual operating current ( I∆n ) of the RCD, operation should occur within 200 mS.

General purpose RCD to BS 4293 incorporating an intentional time delay With a leakage current flowing
equivalent to 100% of the rated residual operating current ( I∆n ) of the RCD, operation should occur within a time range from 50% of
the rated time delay plus 200 ms to 100% of the rated time delay plus 200 ms.

Test to confirm suitability for use to provide additional protection :

The purpose of this test is to confirm the continued suitability of an RCD having a rated residual operating current ( I∆n ) not exceeding 30 mA to
provide additional protection under no-fault conditions ( in the 16th Edition, this was known as supplementary protection against direct contact ).
The test should be performed in both the positive and negative half-cycles.

Test procedure -
With a leakage current flowing equivalent to 500% of ( i.e. 5 times ) the rated residual operating current ( I∆n) of the RCD,
operation should occur within 40 ms.

Confirmation of the effectiveness of the integral test facility :

RCDs have an integral test device to simulate the passing through the detecting device of a residual current. This makes possible periodic testing of the ability of the residual current device to operate. However, it should be remembered
that operation of the integral test button merely confirms the continuing functioning of the electrical and mechanical components of the
RCD. It does not confirm that the device is capable of operating in accordance with the specification of the relevant product standard
or, indeed the requirements of the requirements of BS 7671.

Test procedure - With the supply to the RCD switched on and with the RCD in the “on” position, the button
marked “T” or “Test” on the RCD is pressed. The RCD should switch off. ( 514.12.2 ) recommends that the integral test button of an RCD
is pressed quarterly ( every 3 months ).

Summary :
RCDs should be tested at 50% , 100% and, if providing additional protection 500% of their rated residual operating current ( I∆n ) . In addition, the integral test device should be operated quarterly. Where an RCD is employed to achieve the disconnection time
required by Table 41.1 it is necessary to confirm that the maximum earth fault loop impedances (Zs) stated for a particular sensitivity of RCD in Table 41.5 are not exceeded in the circuit to which they provide protection. More in depth descriptions of both
RCD and earth fault loop impedance testing procedures are given in IEE Guidance Note 3 Inspection and testing