Re-take - Useful Information for 2394 :

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2394: The Regulations Must - State the Facts .

Willcome in on both angles . Q / As .

Themaximum allowed voltage-drop on a lighting circuit is :
Themaximum voltage drop allowed for a lighting circuit in a consumers lighting .supplied by a public ( LV) system is :

• 11.5% .
• 10% .
• 0.75 .
• 3% .

2394:-Re-cap . Table - 4Ab - Voltage-drop - ( Vd ) . p.314 .
i). ( LV ) Low-voltage installation supplied directly from a public low voltagedistribution system . Lighting - 3%. ( 3 x 230V ÷ 100 = 6.9V )
ii). ( LV ) Low-voltage installation supplied directly from a public low voltagedistribution system . Lighting - 5%. ( 5 x 230V ÷ 100 = 11.5V )

 

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Cable- surrounded by Thermal - Insulation .

2394: Coming in on both . angles Q / As

A ( de-rating-factor ) . of 0.88 is applied to cables travelling throughthermal insulation . how thick is this thermal insulation :
• 200mm .
• 100mm .
• 500mm .
• 50mm .

Cablesurrounded by thermal insulation for 400mmor more has a ( de-rating-factor ) of :
• 0.63 .
• 0.51 . Table - 52.2. p.129
• 0.55 .
• 0.5 .

 

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Whenautomatic disconnection of supply is used as a measure of protection .additional protection by RCD shall be provided for :
• Mobile equipment having a rating of greaterthan 32A .
• Socket-outlets in commercial and industriallocations .
• Only for sockets rated at 32A or less whereit is reasonable to expect they may be used to supply equipment for the useoutdoors .
• Socket-outlets rated at 20A or less in a domesticinstallation . 411.3.3.

i). Socket-outlets with a rated-current not exceeding - 20A that are forthe use by . Ordinary-persons. and are intended for general-use .

The maximum-measured-value for aBS-EN-60898 - 20A Type-B . circuit-breaker . is ( in orcase only ) Table . 41.3
• 2.30Ω . -Table . 41.3. & Appendix - 14 . p.424 .
• 2.87Ω.
• 1.44Ω.
• 2.27Ω.

 

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2394: Exams.

Q). The load-current in any part of aRing-final-circuit . should be unlikely exceed for long periods the current-carrying-capacity of the cable . this can be achieved by .

Regulations must state the facts . Appendix - 15 - ( Informative ) p.425

The load-current in any part of a Ring-final-circuit . shouldbe unlikely exceed for long periods the current-carrying-capacity of thecable . Regulation - 433.1.103 .
This can be achieved by .

i) . Locating socket-outlets to provide reasonable sharing of the load around the ring . Appendix - 15

 

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Somefacts : 16[SUP]th[/SUP]Edition . End - OFF .

regulations containing a bath or shower . a requirement to provide allcircuits installed in the location with additional-protection .30mA RCD . is now- included .
this effectively . ends the old-argument . whetheror not to provide RCD - protection for anElectric-shower . not previously a requirement of . BS-7671: provided the circuit-overcurrent-protection . operated automatically within the required-disconnection-time. time under earth-fault-condition . but was commonly recommended in . manufactures-installations for equipment and often left the designer of the installation with the dilemma of whether or not to provide the RCD .

Regulations- 701.411.3.3. RCDs . Additional-protection by RCD. Containing a bath or shower

 

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2394: (T) Regulation - 132.13. . p.20
“Every electrical-installation shall be provided with (Appropriate-documentation ) including that by . Regulation - 514.9 . Part-6 . and where applicable - Part - 7 “

 

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2394: Regulation - 131.3.2. Down-lights . ( Roomfor Thought )

Persons. livestock . fixed-equipment and fixed-materials ( Adjacent to electrical-equipment ) shall be protected against harmful-effects of Heat or thermal-radiation emitted by electrical-equipment .

- Could combustible-dust and debris build up behind the Lights . !!!!

The ( Most - common ) Older-lath and plaster ceilings . sawdust or split-timber laths remaining . ( Couldthe light-fitting(s) become in contact with the down lights .

Facts:
i). Combustion . ignition or degradation of materials’ .
ii). Risk of burns .
iii). Impairment of the safe-function of installed-equipment .

Regulations tells us . Electrical-equipment shall Not - present a fire-hazard to adjacent-materials’ .

 

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The ( Most - common ) Older-lath and plaster ceilings . sawdust or split-timber laths remaining above the light - fitting . become in contact with the down lights .

 

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2394: Problems . Down-lights .

Most-common when Open-backed-recessed-light-fittings . are being used. - Could combustible - dust and debris build up . Heat . you nothe rest .

 

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2394: Down-lights . ( Room for Thought )

Regulation- 522.2.1. External - heat - sources .

In order to avoid the effects of ( Heat !! Cables ) from external-sources . on or more of the following- methods or an equally-effective-method shall be used to prevent a wiring - system .

i). Shielding .
ii). Placing sufficiently far from the source of Heat . ( Cables. Not resting over the down-light . ) Etc ..
iii). Selecting a system with due regard for the ( Additional -temperature - rise) which may - Occur .

 

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ApprovedDocument P - Building Regulations . 2008:

Designand Installation . - ( Applying to Dwellings )
Regulation- P1 .
“Reasonable provision shall be made in the design and installation of electricalinstallations in order to protectpersons operating . maintaining or altering the installations from . fire or injury .

Firstly : 134.1. - Erection . Strictly only applies to Erection not Design .

BS-7671:2011: Are - reminding Us .
Regulation- 134.1.1. Good workmanship by competent-persons or persons under their supervisionand proper-materials shall be used in the erection of the electrical-installation. Electrical - equipment shall be installed in accordance with the ( Instructions provided by the manufacturer of theequipment )

Manufacturer’s- Instructions

As electrician’s . ( we’ve all fallen ) into the trap of not reading the instruction-leaflet supplied with equipment . after all . who needs instructions for things that we have done countless timesbefore .

Misconception- that any experienced-electrician will not need this Guidance . This is clearly not the case . since -differing - products . from differing Manufacturer’s. installed in different-locations will have quite-unique requirements thatshould be considered and implemented .

Inall cases . by simply following . Manufacturer’s - Instructions gives us a ( Fall - back - position ) should something fail or cause a problem. This if nothing-else. will assist the electrician in protecting his or her ( future-liability )

Regulation- 132.13 .
“Every electrical - installation shall be provided with appropriate-documentation. including that required by . Regulation - 514.9. Part - 6 and where applicable . Part - 7 .

Re-cap: Part - P : Extracts’
Installations in dwellings . to operate at a . Low or Extra-low-voltage . The Extra-low-voltage-band was included to cover such things as . Extra-low-voltage downlights . caused of a number of house - fires .

Some- Facts . 2394: “ Downlights “
- Theproblem and risk is further-compounded by the facts that some-lamp-types are designed to ( Direct ) much of their heat out of the back - ( Dichrioic-type) :banghead:
-Whilst others are deigned to direct their heat ( Forward ) - ( Aluminium-reflector-type ) :svengo:

 

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Regulation must - State the Facts .

If you don’t use it you lose it . 2008:

When considering is . supplementary-bonding . canbe Omitted from a location containing a . bath or shower . the Maximum-résistance . of Extraneous-conductive-parts connected to the . ( MET ) main-earthing-terminal . 415.2.2.

• 1.666Ω .
• 0.05Ω .
• 0.5Ω .
• 6.5Ω .

Useful-Junk. Additional-protection - Supplementary-equipotential-bonding .

415.2.2. Where doubt exists .
Regarding the effectiveness of Supplementary-equipotential-bonding. it shall be confirmed that the résistance ( R ) between simultaneously accessible . Exposed-conductive-parts and . Extraneous-conductive-parts . fulfils the following-condition :

R ≤ 50 V /Ia . in a.c. - systems .

Where ( Ia ) is the operating-current in ampere’s of the protective-device . - for RCDs - IΔn . for overcurrent-devices . the current causing automatic operation in 5s .

RCD - 30mA ÷ 1000 = 0.03A .

Example - 1 : Scenario . that the protective-device is an RCD - rated at 30mA . [ R ≤ 50V / Ia ]
R ≤ 50V / 0.03A = 1.666Ω . [ R ≤ 1.666Ω ]

Therefore. a maximum-résistance of 1.666Ω will ensure there is sufficient-current to operate the RCD .
Note : that the touch-voltage may rise above 50V . the value of 50V is used as a constant in the formula to ensure . sufficient-current is following to operate the RCD.

Example - 2 : Scenario . that the protective-device is a .BS-EN-60898 - Type - B circuit-breaker . rated at 32A . first we must establish the current causing operation of the circuit-breaker by referring to the correct . time / current - characteristics graph in Appendix- 3 of BS-7671:2008:2011: therefore . looking at fig- 3.4 . 3.4A . p.249 / 301 . some of us still have marking on 2008 : we can establish that the current-causing-operation of the circuit-breaker is 160A .

[ R ≤ 50V / Ia - R ≤ 50V / 160 - R ≤ 0.31Ω ]

Therefore. a maximum-résistance of .0.31Ω will ensure there is sufficient current to operate the circuit-breaker within five-seconds .

fig- 3.4 . 3.4A .
The current-causing operation of the device between . 0.1 & 5s isthe same . this will not be the case for . “ Fuses “ if many circuits are present in a particular area . and are protected by different-protective-devices / types . etc . the worst-case characteristics should be used .

GN-3: advises that the résistance of Supplementary-equipotential-bonding-conductors. should be no more than ( 0.05Ω ) when verifying Supplementary-equipotential-bonding-conductors. Regulation - 612.2.1. requires that a continuity-test be made with a recommendation that the test-instrument has a .non-load voltage of between . 4V and 24V d.c. or a.c. and a short-circuit-current of .not less than 200mA .

Re-cap: Regulation - 701.415.2. . Supplementary-equipotential-bonding . the regulation states that where the location containing a bath or shower in abuilding with a protective equipotential-bonding system in accordance with . Regulation - 411.3.1.2. Supplementary-equipotential-bonding . may be omitted where all of the following conditions are met .

iv) . all final-circuits of the location comply with the requirements for automatic-disconnection according to . Regulation - 411.3.2.
v). all final-circuits of the location have additional-protection by means of an RCD . in accordance with . Regulation - 701.411.3.3.
vi). All - extraneous-conductive-parts of the location are effectively connected to the protective-equipotential-bonding accordance to . Regulation -411.3.1.2.

this means the Inspector . needs to make an assessment that all . extraneous-conductive-parts of the location are effectively connected to the. protective- equipotential-bonding .according to - 411.3.1.2.

Note: the effectiveness of the connection of . extraneous-conductive-parts in the location to the . main-earthing-terminal may beassessed . where necessary . by theapplication of Regulation - 415.2.2.

Regulation- 415.2.2. States .
Where doubt exists regarding the effectiveness of Supplementary-equipotential-bonding. it shall be confirmed that the résistance ( R ) between simultaneously-accessible . exposed-conductive-parts , and extraneous-conductive-parts . fulfils the following conditions: [ R ≤ 50V / Ia . in a.c. systems ] where .

Ia . is the operating-current in amperes of the protective-device for RCD . ( IΔn ) for overcurrent-devices .the current causing . automatic-operation in ( 5s )

 

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Continuity - confirmed :

During any verification process to confirm the soundness ofan electrical installation - whether it be a new installation, an alteration oraddition, or whether examining the condition of an existing installation - thecontinuity of conductors has to be confirmed.

The requirements of Regulation - 612.2.1 and Regulation - 612.2.2 of BS7671:2011: regarding the continuity ofprotective conductors are generally well understood. However, the implicationsof not testing the line and neutral conductors for continuity are often notfully appreciated.

Why do we carry outcontinuity-tests :

Firstly, it is to ensure that any earthing system is acontinuous and a low resistance path to allow the passage of fault currents ofsufficient magnitude to operate the protective device during fault conditionswithin the required disconnection time.

Secondly, confirmation of the “ zero ” potential between metal parts, both extraneousand exposed-conductive-parts, within an installation to reduce the effects ofelectric shock for the user of the electrical installation.

Thirdly, that the conductors, including all line and neutralconductors, are connected in the correct sequence for safety and foroperational purposes.

Polarity,
Although not directly part of continuity testing, doesfacilitate the confirmation that conductors are continuous and connected in thecorrect sequence.
Earth fault loop impedance testing is part of the ( Verification processof the continuity of the conductors ) , although this test on its owndoes not prove that all conductors are continuous.

One of the areas that are oftenoverlooked is the continuity of neutral conductors. ( Apartfrom ring final circuit continuity testing ) , there is no requirement in BS 7671 toverify the continuity of neutral conductors. Nor is there any facility in thecertificates to record neutral continuity.
( ring final circuit continuitytesting ) Generic schedule of test-results . p.402 . Ring-final-circuit-continuity - L . N . CPC .

2394: Condition of circuit-accessories -621.2. (iii) confirmation that the installation is notdamaged or deteriorated so as to impair-safety . PIR .

- Operation of main-switches- function - check . 612.13.2.
Equipment . such as switchgear and controlgear assemblies .drivers . control and interlocks . shall be subjected to a functional-test . to show that it is properlymounted . adjusted and installed in accordance with the relevant requirementsof these Regulations .

- Manual operation of circuit-breakers. & RCDs to provide disconnection - 612.13.2.

 

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Useful - Junk

New numbering system introduced for UK - only national regulations
Amendment - 1 :2011: . UK national regulations will end in [ 100 . 101 . 102 ] Etc 522.6.102 .

The reason : This will show regulations that are specific to the UK - only . and Not used in the EU . :icon_bs:

 

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• The structure of the newElectrical Installation Condition Report (EICR) remains the same - it has thereport pages and associated schedule of inspections and schedule of testresults. All of these are included in what ? Isit:

A - Model forms in Appendix 7 of BS 7671:2008(2011)

B - Model forms in Appendix 6 of BS 7671: 2008(2011) p.389
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C - New section 710 of BS 7671:2008(2011)

A - Model forms in Appendix 7 of BS 7671:2008 (2011)- [ Harmonized cable core colours ]
C - New section 710 of BS 7671:2008(2011) - [ Medical locations ]

2394 : • What should be recordedin the summary of observations section ( K ) on the report ? Is it:

Answer - One of the following codes ← . as appropriate . has been allocated to each of the observations made. Etc

A - Any C1, C2 or C3 classification code - p.397
​

B - All C4 classification codes
C - The new C5 classification code (as well asall others)