Re-take - Useful Information for 2394 :

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2015 - 530.3.4 :icon_bs:
For an installation with a 230 V single-phase supply rated up to 100A that is under the control of ordinary persons, switchgear and controlgear assemblies shall either comply with BS EN 61439-3 and Regulation 432.1 or be a consumer unit incorporating components and protective devices specified by the manufacturer complying with BS EN 61439-3, including the conditional short-circuit test described in Annex ZA of the standard.

Appendix 1 ( normative ) P/309
BS EN 61439-3:2012.
Low-voltage switchgear and controlgear assemblies, Distribution boards intended to be operated by ordinary persons (DBO)
Intro to Amd 3
421.1.201 , 530.3.4.

421.1.201 Within domestic (household ) premises, consumer units and similar switchgear assemblies shall comply with BS-EN61439-3 and shall:
(i) have their enclosure manufactured from non-combustible material, or
(ii) be enclosed in a cabinet or enclosure constructed of non-combustible material and complying with Regulation 132.12.

Note 1: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.
Note 2: You know the rest . 1[SUP]st[/SUP] of January 2016 .

 

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2015 - O.S.G. 2.2.6. Consumer unit assemblies :book: :svengo:

421.1.201 Where a consumer unit is installed in domestic (household ) premises, domestic garages and outbuildings, one of the following applies:

► the enclosure manufactured from non-combustible material, or
► the consumer unit is enclosed in a cabinet constructed from non-combustible material

Note: This requirement will be effective from 1[SUP]st[/SUP] January 2016, although implementation before this date is not prohibited.

Ferrous metal, i.e. steel is deemed to be an example of a non-combustible material.

plastic enclosures manufactured from 960 degree glow-wire rated material would NOT be classified as “ non-combustible material ” in the context of this regulation .

Where a steel consumer unit is installed in an installation forming part of a TT system, the earth fault loop impedance Ze, is likely to be much higher than that permitted by the overcurrent protective device, i.e. cut-out. Should the tails become loose or damaged and make contact with the metal enclosure, it is likely that the overcurrent device will NOT operate within 5s . The IETs Wiring Regulations Policy Committee, therefore, advises the following:

(a) Consideration should be given to the selection and installation of a class 11 metal consumer unit when used on installation(s) forming part of a TT system. The consumer unit must have been validated as non-combustible using an appropriate test method such as an internal hot wire test and that the metal enclosure does not make contact with any line conductors in the event of an internal fire. Individual manufactures will be able to advice on products which meet these requirements, or

(b) A Class 1 metal consumer unit is installed and each outgoing circuit is protected by an RCBO.
(c) A split, Class1 metal consumer unit is installed, where the double-pole main switch of the consumer unit should incorporate an S type ( time delayed ) RCCB ,e.g. 100mA S - type RCCB.

Note: In cases where RCBOs protect each outgoing circuit. the risk of the solid busbar ( connecting the supply side of each RCBO ) making contact with the ferrous enclosure is minimal. In split consumer units, where two or three RCCBs protect multiple circuits through individual circuit-breakers, the risk of the single-insulated conductors ( connecting the load side of the double-pole main switch to the supply side of the RCCBs) making contact with the ferrous enclosure due to vibration and / or abrasion or being damaged is far higher. In essence, where the construction and layout of the consumer unit is such that the risk of live conductors making contact with the ferrous enclosure is minimal, then the double-pole main switch need not incorporate an S - type RCCB.

In all cases:
522.8.1.
(a) the tails need to be protected to avoid mechanical damage and disturbance at the incoming terminals in the consumer unit in order to avoid the line conductor becoming disconnected or damaged and making contact with the metal enclosure. e.g. clipping or clamping the tails, or installing in trunking and the use of a suitable cable-entry gland, In all cable entry arrangements, the enclosure shall not have sharp edges that could damage cables.

416.22. 416.22.1.
(b) entry point of the meter tails into the metal consumer unit must maintain the fire protection of the consumer unit so far as reasonably practicable. In essence, this means maintaining the requirement for the horizontal top surface of the enclosure to provide a degree of protection of at least IPXXD or IP4X and, elsewhere, IP2XC after installation in accordance with the manufacturer’s instructions as required by BS-EN-61439-3

522.8.1. 521.5.1.
(c) the meter tails also need to be protected to avoid any foreseeable damage and must enter a ferrous enclosure through the same entry point.

A non-combustible enclosure includes base, cover, door and any components, e.g. hinges, covers, screws and catches necessary to maintain fire containment, Devices and blanks are contained within the non-combustible enclosure and therefore, do not have to be manufactured in a non-combustible material e/g. steel, however, the use of non-combustible blanks is NOT precluded.

Where the consumer unit is to be located in an external non-habitable building, e.g. garage or shed, which is not in close proximity to a dwelling, consideration could be given to installing a consumer unit of non-ferrous construction, The term “ not in close proximity ” is always a moot point and the decision to install a non-ferrous enclosure must be supported by a documented risk assessment and must be appended to the Electrical Installation Certificate.

Useful junk . Belling Out - Slang for testing installations

 

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With your exams, PS the right word is used in Chief Examiner report. .

2015 . GN-3 have (( boldly marked out some important items )) in pages now :book:

2.6.17. Prospective fault current ( Ipƒ ) from wording(s)

434.1 Regulation 612.11. introduces the requirements of Regulation 434.1. into the testing section, the designer being required to determine the prospective fault current, under both short-circuit and earth fault conditions , Etc , at every relevant point of the installation ......

With the power on, the maximum value of the prospective short-circuit current can be obtained by direct .......... etc.

 

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Why is GN-3 & BS-7671:2015 so important in Exams . the Questions will be taken from these books .

The Regulation have to states the facts .
GN-3 , is Guidance , with BS-7671:2015 . Do you want , C&Gs “ Nil Pwa ” for their effort :13:

2015 GN-3 : Same wording .

For consumer units or distribution boards not at the origin, there can arise confusion over the term “ external earth loop impedance ” (Ze) and some prefer to write or note the earth fault loop impedance at the distribution board as Zdb. As this value is not external to the installation, the formula is modified to : ................ Zs + Zdb + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] )

 

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re-cap 2015. “Making you Aware ” .

411.4.5. 411.5.3. Guidance Note 3 tell us , . Operation of residual current devices .
For each of the tests, readings should be taken on (( both )) positive and negative half-cycles and the longer operating time recorded . ( 0° / 180° )

Because we use a Megger Multifunction Tester’s it does it Automatically . everything is all right NO . C&Gs “ Nil Pwa ” for their effort .. does it make us complacent !!

 

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RCDs are used to provide protection against the specific dangers that may arise in electrical installations, including:

• Fault protection.
• Additional protection.
• Protection against fire.

An RCD does not provide protection against overcurrent. Overcurrent protection is provided by a circuit-breaker . BS-EN-60898-1

 

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GN-3 Purpose of Initial verification . 611.2.
Chapter 61 of BS-7671:2008: states the requirements for “ INITIAL VERIFCATION ” As far as reasonably practicable, an inspection shall be carried out to verify :

GN-3 Purpose of Initial verification .
BS-7671:2011: provides a format list in Regulation 611.2. of items to be verified, again so far reasonably practicable; these as follows:

(A3 ) GN-3 Purpose of Initial verification .
BS-7671:2015: provides a format list in Regulation 611.2. of items to be verified, again so far reasonably practicable; these as follows:

Q) State the document that should accompany an Installation Electrical Installation Certificate or Electrical Installation Condition Report .

GN-3 P/12 . 1.3.1. ( Certificates and Reports )
(i) Schedule of items inspected .
(ii) Schedule of test results .

Following the initial verification of a new installation or changes to an existing installation.
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 meaning the installation work ” not the work of carrying out the inspection and testing. Likewise, following the periodic inspection and testing of an existing installation, an Electrical Installation Condition Report, together with schedules of inspection and schedules of test results, are required to be given to the person ordering the inspection .

Part of. Inspection checklist . :book:

GN-3 . Cooker control unit .
(a) Sited to one side and low enough for accessibility and to prevent flexes trailing across radiant plates . 522.2.1.
(b) Cable to cooker fixed to prevent strain on connections . 522.8.5.

 

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PS. have you looked :30:

From the IET . Books 2015.

Amendment(s) 3 - 2015
To discourage counterfeiting and help customers to recognise genuine copies of the IET Wiring Regulations, the IET has placed a hologram on the inside front cover of three of its new titles:


• BS 7671:2008+A3:2015
• On-Site Guide to BS 7671:2008+A3:2015
• Guidance Note 3, 7th Edition

The hologram contains the IET logo in large print and small and the word “ GENUINE ”, as well as a number of hidden measures, including text that is visible with a magnifying glass.

 

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O.S.G. :book:

Installation and use of Non-standard cables.

133.1.1. 511.1. 511.2.

For the purpose of this guidance publication and ensuring compliance with BS-7671: the installation and use of non-standard cables, such as
SY, CY, and YY cables is discouraged.

The letters signify:

S - steel braid
Y - PVC
C - copper braid

To identify:

SY cables - steel braided, usually translucent sheath, PVC insulated flexible conductors.
YY cables - usually gray PVC sheath, PVC insulted flexible conductors.
CY cables - tinned copper wire braid, usually gray PVC sheath, PVC insulated flexible conductors.

To meet the requirements of BS-7671: every item of equipment must comply with a British or Harmonized Standard, in the absence of such, reference can be made to IEC standards or the appropriate standard of another country, SY , YY and CY cables are NOT made to British or Harmonised Standards.

This is NOT deemed sufficient for the purposes of BS-7671:

it is important that cables have approval from an independent testing organisation and installers should ensure that all cables purchased have manufacturers’ identification and a specification reference/standard number printed on the sheath to ensure testing, if necessary, and traceability .

 

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O.S.G. :book: P/84

On-Site Guide is designed to be taken on-site for easy referencing and provides simple guidance on the application of BS-7671:

Consumer units in dwellings .

With BS-7671:2008+A3:2015: the requirements for non-combustible consumer units was introduced.

installers adding or amending circuits in dwellings will encounter older consumer units, i.e. those not complying with Regulation 421.201, for many years to come. it is important that installers do not advise the replacement of consumer units simply because they don’t comply with the current version of BS-7671:

To ensure the ongoing use of such enclosures and assemblies, the installer must ensure the following :

(a) confirmation that ALL conductor connections are correctly located in terminals and are tight and secure; this may involve seeking the advice of the manufacture of the equipment to establish correct torque setting for screwdrivers when checking terminals. This applies to all conductor/busbar connection within the consumer unit, not just those relating to the addition or alteration .

(b) there are no signs of overheating.
(c) all covers, shields and barriers supplied when originally installed are present and in good, serviceable condition .

it must be verified for all conductor/busbar connections:

(i) not clamping on insulation .
(ii) conductor not damaged e.g. through “ incision ” on a solid conductor during insulation removal, or strands removed .
(iii) conductors are correctly placed, for example on the correct side of a moving plate in a cage-clamp terminal .
(iv) permitted number of conductors per terminal is not exceeded .
(v) no undue strain on the electrical connection, particularly incoming tails

So far as is reasonably practicable, confirm that incorporated components such as a Main Switch, circuit-breakers, RCBOs, RCCBs etc ., are not subject of a product recall . This could be achieved by direct question to the manufacturer .

 

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O.S.G. Electrical supplies to Furniture :book:

My point .

543.2.1. 543.2.6.
There is no general requirement to ensure electrical continuity across the metallic frame of an item of furniture unless the frame has been designed to be used as a protective-conductor .

 

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3.1. O.S.G. Protective device - 2008 & 2011. ◄ Passed tense
The consumer unit ( or distribution board ) contains devices for the protection of distribution circuits and final circuit against:

i) overload
ii) short-circuit
iii) earth fault ........... Etc

Functions i and ii are carried out usually by one device, i.e. a fuse or circuit-breaker.
Function iii may be carried out by the fuse or circuit-breaker provided for functions i and ii or by an RCD

An RCBO, being a unit with a combined circuit-breaker and RCD, will carry out functions i, ii, and iii .

Things has changed . (A3) 2015 . ▼ :book:

3.1. O.S.G. Protective device
The consumer unit ( or distribution board ) contains devices providing:

(a) Overload protection ✓
(b) Short-circuit protection ✓
(c) Fault current protection ✓
(d) Additional protection: RCD(s) ✓

Functions a, b, and c, are usually carried out by one device, i.e. a fuse or circuit-breaker.
An RCBO, being a unit with a combined circuit-breaker and RCD, will carry out functions a, b, c, and d .

 

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Learning curve only .

GN-3 . 2008: ◄ :book:

4) rule of thumb figures .
As a rule of thumb, the measured value of earth fault loop impedance for each circuit at the most remote outlet should not exceed 0.8 of the relevant value in the BS-7671 tables. This takes into account the increase of résistance of the conductors with the increase of temperature due to load current and errs on the side of safety .

Another method is to use the rule of thumb as described in Appendix 4 of BS-7671:2011: ◄

Circuit has a measured Zs of 0.51Ω
BS-EN-60898-1 circuit-breaker . Type C 32A
Table 41.3 . maximum permissible Zs for the circuit is 0.72Ω

multiply the maximum permitted value by ( 0.8 ) 0.72 x 0.8 = 0.57Ω ( This now becomes the maximum permissible value ))

Question is . Higher or lower .

As the measured value is less than . ?? will the circuit be acceptable .

BS-7671:2015 ◄
Using a factor of 0.8
Table 41.3 . maximum permissible Zs for the circuit is 0.68Ω
BS-EN-60898-1 circuit-breaker . Type C 32A

 

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Learning curve only . (( Look at the dates ))

Q ) When taking impedance measurement at ambient temperature a rule-of-thumb correction factor may be applied to the values in BS-7671: to take into account the increased résistance of the conductors due to load current is ?

0.75
0.8
0.5
1.2

GN-3 BS-7671 Amd 1 2002. ◄ Past tense :book:


4) Rule of Thumb figures ( 0.75 )
As a rule of thumb, the measured value of earth fault loop impedance for each circuit at the most remote outlet should not exceed three-quarters of the relevant value in the BS-7671 tables. The three-quarters figure allows for a reduced cross-section protective conductor and errs on the side of safety.

GN-3 . ◄ :book:
2008:
2011:
2015:

4) rule of thumb figures (0.8)
As a rule of thumb, the measured value of earth fault loop impedance for each circuit at the most remote outlet should not exceed 0.8 of the relevant value in the BS-7671 tables. This takes into account the increase of résistance of the conductors with the increase of temperature due to load current and errs on the side of safety .

 

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411.8.1.3. Requirement for fault protection . :icon_bs:
Extracts : 2015
Where a circuit-breaker is used, the maximum value of earth fault loop impedance (Zs) shall be determined by the formula in Regulation 411.4.5.

Alternatively, the value specified in Table 41.6. may be used instead of calculation for the nominal voltages (Uo) and the types and ratings of overcurrent devices listed therein .

Reduced low voltage system(s) :icon_bs:

Table 41.6.
Maximum earth fault loop impedance (Zs) for 5s disconnection time and Uo of 55V (single-phase) and 63.5V (three-phase)
see Regulations 411.8.2. and 411.8.3.

BS-EN-61558-1:2005+A1:2009
411.8.4.1. (i)
717.411.6.2. (ii)
717.413.

BS-EN-61558-2-23. Particular requirements for transformers for construction sites.
411.8.4.1 (i)

Voltage of 65V to earth, three-phase.
55V to earth , single-phase will give protection against severe electric shock .

They therefore recommended that portable tools used on construction sites . etc 110V centre-tapped transformer .

What’s new . (A3) - 2015 .

Note 1: The circuit loop impedance's have been determined using a value for factor Cmin of 0.95.
Note 2: The circuit loop impedance's given in the table should not be exceeded when:
(i) the line conductors are at the appropriate maximum permitted operating temperature, as given in Table 52.1. and
(ii) the circuit protective conductors are at the appropriate assumed initial temperature, as given in Table 54.2. to 54.5.

if the conductors are at a different temperature when tested, the reading should be adjusted accordingly, see Appendix 14.

Note 3 : Where the line conductor insulation is of a type for which Table 52.1. gives a maximum permitted operating temperature exceeding 70°C, such as thermosetting, but the conductor has been sixed in accordance with Regulation 512.1.5:
(i) the maximum permitted operating temperature for the purpose of Note 2 (i) is 70°C and
(ii) the assumed initial temperature for the purpose of Note 2 (i) is that given in Tables 54.2. to 54.4. corresponding to an insulation material of 70°C thermoplastic.

Note 4 : Data for fuses of rating exceeding 200A should be obtained from the manufacture.