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

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“ Rcd's “

Fire detection circuits must be supplied independently of other circuits and not protected by an Rcd protecting multiple circuits. 560.7.1 All circuits in a bath shower room must be protected by a 30mA RCD. P166, 701.411.3.3
Where applicable an RCD notice must be fixed on or next to the CCU 514.12.2 An RCD should not be used as a main switch 314.2 If the maximum Zs values for a circuit in a TN systems cannot be met, the circuit may be protected by a 30mA RCD. 531.3.1
If the maximum Zs values for a TN systems cannot be met, the installation may be protected by an 100mA RCD and treated as a TT systems . 531.3.1 : 411.5.1 : 411.5.2 : 411.5.3
Unless specifically labelled or suitably identified, all 13A socket outlets must be protected by a 30mA Rcd. 411.3.3
In a TN systems , the part of a lighting circuit in a bath or shower room is required to be 30mA RCD protected. 411.3.3 , 701.411.3.3

Where a cable is buried in a wall or partition at a depth of less than 50mm on either side it must be sufficiently mechanically protected against penetration OR RCD protected AND installed either horizontally within 150mm of the top of the wall or vertically within 150mm of the angle formed where two walls meet or run horizontally or vertically to an accessory, luminaire or CCU 522.6.6 , 522.6.7 . This applies to a cable in a partition constructed using metallic parts other than fixings irrespective of the cable depth. 522.6.8

Surface run cables do not require RCD protection. OSG p22

A single RCD protecting a TT systems must be installed at the origin of the installation unless the part of the system between the origin and the RCD fulfils the requirements for protection by Class 11 equipment or equivalent insulation 531.4.1

All Electrical equipment must be accessible for operation , inspection & testing maintenance and repair. 132.12

Rcd Test Procedure

Many RCD test meters have a facility where tests can be carried out during the positive or negative half of the supply cycle. For tests 1 & 2 the RCD operating time to be recorded is the longer of the two measured during the half cycle tests.

DO NOT press the test button on the RCD before testing as this can temporarily reset a faulty RCD

Test 1
Adjust the current setting on the test meter to 100% of the rated trip current of the RCD and perform a test. A general purpose BS4293 RCD should operate within 200mS . A general purpose BS-61008 RCD or RCBO to BS-61009 should operate within 300ms

Test 2
An RCD provided for Basic Protection should have a rated TRIP current not exceeding 30mA If the RCD is rated at 30mA , adjust the current setting on the test meter to 150ma ( x5 ) and perform a test. The RCD must operate in a time not exceeding 40mS.
Test 3
Adjust the current setting on the test meter to 50% of the RCD trip current and perform a test. The RCD should not operate within 2 seconds
The Test Button : Finally operate the RCD by pressing its test button

 

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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 :

 

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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 )

 

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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 :

 

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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 :

 

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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 :

 

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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 ,

 

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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 :

 

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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.

 

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*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.

 

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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).

 

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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.

 

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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 )

 

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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

 

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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.

 

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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 )