Re-take - Useful Information for 2394 :

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Useful-Junk:

Earth-fault-loop-impedance: 612.9. ( Circuit-loop-impedance )

The method of testing involves connecting the tester between Line & Earth .
When the test is started , a current is passed around the circuit and supply and the loop-impedance ismeasured .

Some-tester(s) use a , 2 - lead-connection
While some use 3 - leads

The only-difference is that the , 2 - lead-tester , powers the instrumentfrom Line and Earth , whilst the 3 - lead-tester uses the Neutral , the Neutral-connection can simply be connected to Earth and it will then behave as a 2 - lead-tester .

Table- 41.5.
The Regulations require only that ( Zs) does not exceed 50V ÷ by thenominal-rating of the RCD .
100mA device this would be 500Ω ,
30mA device would be 1667Ω , 50V ÷ 30mA = 1667Ω

30mA ÷ 1000 = 0.03A .
50V ÷ 0.03A = 1667Ω .

( Circuit-loop-impedance ) 612.9. Earth-fault-loop-impedance :
Where protective-measures are used whichrequire a knowledge of earth-fault-loop-impedance . the relevant-impedance(s) shallbe measured . :icon_bs:
[h=1]Blast from the past : ◄ [/h][h=1]Avoiding unwanted tripping of RCDs and circuit-breakers whenmeasuring Zs [/h]Earth fault loop impedance testinstruments using techniques other than conventional high-current testing arerequired to prevent tripping of RCDs and certain types of circuit-breaker

Many earth fault loopimpedance test instruments use a test measuring current of between 20 A and 25 A. This test current can flow inthe earth fault loop for, typically, 40 ms. This relatively high current willusually trip any RCD protecting thecircuit and may also trip some circuit-breakers, suchas Type B overcurrent circuit-breaker to BS EN 60898 having a rated current less than 10 A.

This unwanted operation of a protective device will prevent themeasurement of earth fault loop impedance from being taken and, perhaps moreimportantly, result in an unwanted disconnection of the supply to the circuitunder test.

Solution
The value of earth fault loop impedance (Zs) is required to bedetermined for every distribution circuit and final circuit having AutomaticDisconnection of Supply (ADS) as its protective measure against electric shock.The value of Zs is also one of the values required to be recorded on theSchedule of Test Results in the Electrical Installation Certificate andPeriodic Inspection Report.

Regulation 612.9 indicates that the value of Zs may bedetermined by direct measurement or by an alternative method.

Instrument manufacturers can supply earth fault loop impedancetest instruments that are less liable to trip RCDs and circuit-breakers than isthe case with a conventional high current earth fault loop impedance testinstrument. There are two common techniques that manufacturers employ:

• d.c. biasingthe RCD: this techniqueusers a d.c. bias current to saturate the core of the RCD prior to the testsuch that the actual Zs measuring test current is undetected by the RCD. (It isimportant to remember that this technique is not effective for all types of RCD)
• Testing a reduced current : this technique uses a test current at or below 15mA, suchthat RCDs having a rated residual current of 30mA and greater will not trip. This techniquewill also mean that overcurrent circuit-breakers of Type B with a rated currentless than 10 A should not trip when measuring Zs.
612.9. Earth-fault-loop-impedance :
Where protective-measures are used whichrequire a knowledge of earth-fault-loop-impedance . the relevant-impedance(s) shallbe measured . or determined by an alternative-method .

 

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Protection by Automatic-Disconnection of thesupply .

General: 612.8.1.
The ( Verification ) of theeffectiveness of the measures for fault-protection by (ADS ) depends on the type of system used . TN - system , TT - system .
The Regulations require that :

Compliance shall be verified by .

• Measurement of the Earth-fault-loop-impedance . 612.9.
• Verification of the characteristics and / or the effectiveness of the associated-protective-device .

- for overcurrent-protective-devices . ( By Visual-Inspection ) i.e. short-time or instantaneous-tripping-setting for circuit-breakers, current-rating and type for Fuses

- for RCDs , ( By Visual-Inspection ) and test.
The effectiveness of (ADS ) by RCDs shall be verified using ( Suitable-test-equipment ) according to , BS-EN-61557-6 . see regulation - 612.1 to confirm that the relevant-requirements in Chapter - 41 are met . Etc

 

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Design : 2392-10 .

Two of the most important-requirements for the installation of electrical-equipment are that :

- Installed-equipment and its connections must be accessible for operational , inspection and maintenance-purposes
- Equipment must be arranged to allow easy-access for , periodic-inspection , testing and maintenance.

Junction-boxes can be used if Accessible:
According to Electrical-Safety-Guidelines connections should be easily-accessible and located where there is room to work around them .

Junction-boxes with screw-terminals must be positioned where they can be easily-reached for inspection . testing and maintenance

Fault-finding: ?? . since the loose or disconnected-cables can’t be seen within junction-boxes , ( Stringent-Safety-Standards ) including Part - P . have placed junction-boxes under the spotlight forclose-inspection .

One of the most-Common-faults:
Connections occurs because the same-terminals are used for ( Both the Twin & CPC cables )this means that the thin-strands of aflexible-cables-conductors canbecome damaged , possibly causing a loose-connection .

 

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Electrical Installation Certificate - What are they ?

The Regulations are re-minding us . EIC - p/392

A ( Safety Certificate ) issuedby the electrician on completion of a new electrical installation, or changesto an existing electrical installation. The certificate confirms that the installation has been Designed , Constructed , Inspectedand Tested to the UK nationalstandard BS 7671:2008:2011:

Defects or Omissionsrevealed during inspection and testing shall be made good before the Certificate is issued . 632.4

Defects or Omissions revealed during inspection and testing of theinstallation-work covered by the , Electrical-Installation-Certificate. shall be made good before the certificate is issued .

 

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Useful- Junk .

GN-3: P/80
Periodic-Inspection of the installations to an earlier-edition of BS-7671: or the IEE Wiring-Regulations :icon_bs:

People often ask what standard should be applied when carrying out the periodic-inspection of an installation-constructed in accordance withan earlier-edition of BS-7671: , or aneven-earlier-edition of the IEE Wiring-Regulations or to an unknown-standard .

In this situation the (Inspection ) should be carried out against the current-edition of BS-7671: However , it is likely that therewill be items that do not-comply with the current-edition of BS-7671: but this does not-necessarily mean that the installation is unsafe .

Ifthe inspector feels that an item requires-improvement , it should begiven ( Code - 3 ) on the ,Electrical-Installation-Condition-Report . if the finding does not require-improvement it does not need to be recorded as an observation .

GN-3, reminds us .
Reference is made to ( Existing-Installation) both in the second-paragraph of theintroduction to BS-7671:2008: and in the note by the ,Health & Safety-Executive which follows the Preface to BS-7671:

Regulations: p/12. Notes on the plan of the 17[SUP]th[/SUP]Edition .

2008: p/10 .
The Health & Safety-Executive ( HSE ) welcomes the publication of BS-7671: 2008 . Requirements for Electrical-Installations . IEE Wiring Regulations 17[SUP]th[/SUP] edition . BS-7671: and the IEE Wiring-Regulations have been extensively-referred to in , HSE- guidance over the years . Installations which conform to the , standards laid-down in BS-7671:2008: are regarded by HSE, as likely to ( Achieve-conformity) with the relevant-parts of the Electricity at Work Regulations - 1989 , Existing-installations may been designed & installed to conform to the standards set by ,earlier-editions of BS-7671: or the IEE Wiring-Regulations , This does not mean that they will fail to (( Achieve-conformity)) with the relevant-parts of the . Electricity at Work Regulations - 1989 .

Introduction to BS-7671:2008: p/4.
The Regulations apply to the design, erection and verification of electrical-installations. also additions & alterations to existing-installations .
Existing-installations that have been installed in accordance with earlier-editions of the Regulations may not comply with this edition in every-respect , This does notnecessarily mean that they are unsafe for continued-use orrequire-upgrading . Etc

Regulations: p/12. Notes on the plan of the 17[SUP]th[/SUP] Edition .
2011: p/12 .
The Health & Safety-Executive ( HSE ) welcomes the publication of BS-7671: 2008 . Requirements for Electrical-Installations . IET ( formerly IEE ) Wiring Regulations 17[SUP]th[/SUP] edition . and its upgrading with the first-amendment . BS-7671: and the IEE Wiring Regulations have been extensively-referred to in , HSE - guidance over the years . installations which confirm to the standards laid-down in BS-7671:2008: are regarded by HSE as likely to (( Achieve-conformity )) with the relevant-parts of the . Electricity at Work Regulations - 1989 .

Introduction to BS-7671:2008: p/4.
Existing-installations that have been designed , installed in accordance with earlier-editions of the Regulations may not comply with this edition in every-respect , This does notnecessarily mean that they are unsafe for continued-use orrequire-upgrading . Etc

Regulations- reminds us .
Point to Note : p/2 . 2004: 2008 : 2011: Etc
While the publisher and contributors believe that the information and guidance given in this work is correct . all parties must rely upon their own-skills and judgement when making use of it . Neither the publisher nor any contributor assume any liability to anyone for any loss or damage-caused by any error or omission in the work , whether such error or omission is the result of negligence or any other cause . (( Any and all such-liability is disclaimed ))

GN-3, reminds us . p/2
Point to Note :
While the publisher and contributors believe that the information and guidance given in this work is correct . all parties must rely upon their own-skills and judgement when making use of them . the author, publisher and contributors do not assume any liability to anyone for any loss or damage-caused by any error or omission in the work , whether such error or omission is the result of negligence or any other cause . (( Where reference is made to legislation it is notto be considered as legal-advice )) any and all such-liability is disclaimed .

(( Earlier-Edition 2001 )) ◄◄ How Things Change . over time :svengo:
If there are items that require-urgent-attention . these must be identified . Etc .
A non-compliance that perhaps does not require any further-attention might be 6mm[SUP]2[/SUP] bonding-conductor . This was considered-adequate prior to the 1982 PME - Approvals . but now 10mm[SUP]2[/SUP] is required as a minimum .

Defects : which would be considered dangerous . BS-7671:2008:2011: lack of a (( protective-conductor)) in a lighting-installation , that includes Class - 1 luminaries’ .

 

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InsulationRésistance . ( IR )

713-04-04 . 16[SUP]th[/SUP] Edition :
Where the circuit includes electronic-devices . only a measurement to protective-earth. shall be made with the phase and neutral-connectedtogether . Precautions may be necessary to avoid-damage to electronic-devices .

Regulation 612.3.3.
Recognises the possibility of there being , Electronic-devices installed in a circuit , and requires only a measurement to protective-earth, from Line and neutral-connected together .

It is most important to connect the Line & Neutral together before carrying out thistest .

612.3.3.
Where the circuit includes electronic-devices which are likely to influence the results or be damaged . only a measurement between the , Line-conductors-connected together and the earthing-arrangement shall be made .

Precautionsmay be necessary to avoid-damage to electronic-devices . ( The Whys )
Note : Additional-precautions , such as disconnection , may benecessary to avoid damage to Electronic-devices .

In this Case . The Regulations have stated the Facts . Which it Must-Do .

Regulation - 612.3.2. Recognises .
Disconnection of Current-Using-Equipment .

The insulation-résistance measured with the test-voltages ,indicated in Table - 61 , shall beconsidered-satisfactory if the main-switchboard and each-distribution-circuit-tested ( separately) with all its final-circuits connected but with current-using-equipment-disconnected . has an insulation-résistance notless than the appropriate-value given in Table - 61 .

( The Whys )
If a Line to Neutral-insulation-test is to be carried-out , the disconnection of all Current-using-equipment is necessary , Otherwise the test-instrument will be , Short-circuited by the load-résistance .

 

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Compliance with Standards . What the Regulations are asking You .

Inspection. - 611.1. Inspection shall precede-testing and shall normally be done with that part of the installation under-inspection disconnected from the supply .

611.2.
Requires that a ( Visual-Inspection be made of an installation ) to confirm that all equipment complies with the relevant-requirements . of the applicable British-Standard or Harmonised-Standard .

Inspectors should be looking preferably for an Approved-body-mark . or a maker’s CE - mark and identification of the Standard .
Where the equipment is not covered by a British-Standard or Harmonised-Standard.

You should be asking yourselves . what Action has been taken to ( Verify Compliance with the General-Requirements )

611.2. The inspection shall be made to Verify that the installed-electrical-equipment is Etc.

 

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Regulations - BS-7671:2008:2011: p/12 :icon_bs:

Note: by the , Health and Safety Executive .

A Note : from the Health and Safety Executive ( HSE ) is included as BS-7671: and the IET Wiring Regulations have been extensively referred to in ( HSE - Guidance ) over the years .

It is pertinent to ( Sate - that) BS-7671: is Not a Statutory-Document and it is . Therefore . Therefore Not aLegal-Requirement to follow the practices-referred to within . The legal-requirements are contained within the , Electricity at Work Regulations 1989 ( EWR ) which includes a requirement that all Systems are ,Safe from this requirement BS-7671: provides the framework to which electrical-installations should follow in order to meet therequirements of the Law .

There is reference in the Note : by the HSE . rather like the one-seen . previously in the introduction . which refers to Older-Installations .

Existing-installations may have been designed and installed to conform to the standards set by Earlier-Editions of BS-7671: or the IET WiringRegulations .
This does not mean that they will fail to achieve-conformity with the relevant-parts of the , Electricity at Work Regulations 1989 . Again .
The intent is to make it known that an installation which was not-installed to the 17[SUP]th[/SUP] Edition may not be unsafe and may be suitable for continued-use and . hence does not mean that they will fail to achieve conformity with the relevant-parts of the Electricity at Work Regulations 1989 .

 

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Additions and Alterations

Scenario:

Theexisting-circuit was installed to BS-7671:2001 ( 2004 and completely with that Edition of the standard . no part of thecircuit-protected by an RCD . :13:

Some installers are of the opinion that whenadding to an , Existing-circuit . provided that the existing-circuit meets the requirements of BS-7671:2001 ( 2004 ) the 16[SUP]th[/SUP] Edition , then the 17[SUP]th[/SUP] Edition simply-applies to the ( New-Addition ) 17[SUP]th[/SUP] Edition is to be applied to the entire-circuit-worked ON.

Regulations must Statethe Facts .
Regulations BS-7671:2008: as these opening-paragraphs set the scene .
The first-paragraphs of the introduction to the 17[SUP]th[/SUP] Edition is very-straightforward as it , ( States the effective-date of commencement ) the second-paragraph. however . is a little more-Cryptic .

Existing-installations that have been-installed in accordance with ( Earlier - Editions ) of the Regulations may Not - Comply with this Editionin every-respect . This does not-necessary-mean that they are unsafe for continued-use or require-upgrading .

The 17[SUP]th[/SUP] Edition is to be applied to the entire-circuit-worked on .

Early-pages of - Introduction to BS-7671:2008 . as these opening-paragraphs set the scene .

The first-paragraph of the introduction to the 17[SUP]th[/SUP]Edition is very straightforward as it ( States the effective-date of commencement )
The second-paragraph . however is alittle-more-cryptic

Existing-Installations. that have been installed in accordance with earlier-editions of the Regulations may not-comply with this Edition in every-respect . This does not necessary-mean that they are unsafe forcontinued-use or require upgrading .

 

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Regulations: have stated the Facts . Which they must do .

Therequirements for Additionsand Alterations in BS-7671:2008 are given in a number of Regulations .

p/14 . Very-First-Regulation : 110.1. from the Scopeof BS-7671: States that the Regulations have requirements for :
vi ) Additions and Alterations to installations and also-parts of the .Existing-Installation affected byan Additionsand Alterations

“ Note the words “ …… parts of the existing-installation affected by an Additionsand Alterations in (Part - vi ) of the Regulations
When a circuit is extended . the New-Addition-Alters the characteristics of theexisting-circuit-installation to some-extent.

- The increased-load
- Or the resulting-earth-fault-loop-impedance

Your next Regulation . is the Key - Regulation . 132.16 . p/20 . Additions and Alterations toan Installation .
132.16 . No Additions and Alterations temporary or permanent. shall be made to an existing-installation . unless it hasbeen ascertained that the rating and the condition of any existing-equipment . including that of the distributor . will be adequate for the altered-circumstances . Furthermore .the earthing and bonding-arrangements ,if necessary for the protective-measures-applied for the safety of the Addition and Alteration . shall be adequate

The Regulation requires that if youplan to make any-changes . The existing-installation must be insuch a condition which will be suitable for theintended-alteration .
As is stated .

□ The equipment belonging to the distributor . the condition and size of the supply-cable . The Distinct-Network-Operator’s ► ( Wording Used in Exams - DNO ) cut-out . metering-equipment . supply and meter-tails .

- Distribution-equipment . Switchboard . Consumer-unit ( CCU )
- Earthing and Bonding-arrangements .

If any-part of the installation intended to be altered is ( Not suitable ) it must be brought up to “ Standard “ thestandard being BS-7671:2008:2011:
Where equipment belonging to the , Distributor or metering-company is not suitable for the altered-circumstance .

- Tails are undersized
- Equipment is damaged with Exposed-parts

The Electrician must ensure that the equipment is in safe-condition before undertaking the installation-work .

In most-cases it will be Necessary to arrange for the Distributor and / or Metering-company to attend site and make the changes .
( As weall Known . Usually-incur a Charge ££ )

 

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2392-10 / 2394. ( Certification & Reporting ) Along the Way .

Additions and Alterations in BS-7671:2008:2011: :13:

The Electrician . would not take ( Responsibility ) for any other-circuits within the Installation that they have ( Not-worked-On )

Electrical-Installation-Certificate ( EIC ) has a facility for comments on the Existing-Installation . p/391.

The Electrician should record any . Unsafe-conditions or practices . bring them to the Client-Attention ◄ ◄

This requirement can be found in Regulation - 633.2.

p/196 . 633.2. 2392-10 / 2394 .
The Contractor / Electrician responsible for the new-work , or person authorized to act on there behalf . shall record on the ( EIC ) or the ( MEIWC ) any defects found ,

So far as is reasonably-practicable . in the Existing-Installation .

 

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2392-10/ 2394 .

Verification : 610.4. p/189 .
For an Addition and Alteration to an existing-installation . it shall be Verified that the Addition and Alteration complies with the Regulations and does not impair the Safety of the Existing-Installation .

 

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134.2.1. p/22.
During-erection and on completion of an installation or an Addition and Alteration to an installation and before it isput into service . appropriate ,inspection & testing shall becarried out by competent-persons to verify that the requirements ofthis Standard have been met .

Appropriate-certification shall be issued in accordance with Sections 631 & 632 .

631.1. p/195 . The requirements of Sections 631 and 632 for the issue of an ,Electrical-Installation-Certificate . or a Minor-Electrical-Installation-Work-Certificate. shall apply to all the work of the Additions & Alterations

 

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Legal-Requirements 2009 .

BS-7671:2008:2011: Not a Statutory-document

BS-7671:2008:2011: Primarily : There are two-pieces of Legislation to consider .

Firstly :- being the Electricity at Work Regulations 1989 .
Second :- being the Building-Regulations .

Electricity at Work Regulations 1989 . Applies
Tothese undertaking electrical-work . as part of their Job .

Building-Regulations. Apply
To those undertaking electrical-work as part of their Job . & to those carrying out DIY - Work .

• Electricity at Work Regulations 1989
The ( EWR ) states that all systems are to be safe so as to prevent-danger and prevent the risk of injury .
The Memorandum to the , Electricity at Work Regulations 1989 . HS(R)25 . records that the IET Wiring-Regulations is widely-recognised and accepted in the UK and compliance with them is likely to achieve-compliance with relevant-aspects of the 1989 Regulation in point - 7 of the introduction . Further . point - 9 states that installations to which the IET Wiring Regulations are relevant may have been installed in accordance with an Earlier-Edition . now-superseded but then-current . That in itself . would not mean that the installation would fail to comply with the 1998 Regulations .

Electricians often find that their client-refuses to pay for any-remedial-work required tobring existing-elements of installation up to Standard the installer should always evaluate the existing-situation by carrying out ( Periodic-Inspection ) of the installation prior to starting-work . so that any irregularities can be brought to the attention of the client .

client :- ifthe client-refuses to pay for upgrade(s) then the installer simply doesn’t take on the job .

the issuing of disclaimers . by installers . stating that the client was made aware of Shortfalls in the existing-installation . is no way around the Law . if someone is injured due to negligent-practice . a covering-letter will not-prevent-prosecution .

Building-Regulations. England & Wales requires that
Installations Electrical-Part - P ventilation ( Part - F ) accessibility ( Part - M ) must be no worse in terms of the level of compliance withother-applicable-parts of Schedule - 1 to the Building-Regulations than before the work was undertake .There is a similar-requirement in the . Scottish-Building-Standards handbooks which requires that “ any service-fitting or equipment is to be a standard no worse than at present “

Approved-Document- P states that “ A way ofcomplying is to follow the technical-rules of BS-7671: or an equivalent-standard “

Note : that the use of the Words “ Equivalent-Standard“ therefore a theoretical alternative as BS-7671 is not a
statutorydocument. Currently in the UKno other electrical installation standard exists. Bear in mind that BS 7671 isbased on the technical intent of HD 60364, which in turn was developed from IEC60364 – therefore, they are not equivalent standards.

Conclusion
When carrying out additionsor alterations to existing electrical installations, the reconfigured aspect ofthe electrical installation should comply with 7671:2008. The installer doesnot simply take responsibility for the newly installed or reconfigured elementof the installation but all parts of the circuit(s) worked on - including theneed to comment on the continued suitability or otherwise of the equipmentbelonging to the distributor - this includes the condition of the meteringequipment, supply and meter-tails, distribution equipment and the earthing andbonding arrangements. If the client does not want to pay for upgrades toexisting equipment, this does not absolve the installer from responsibility,nor does a disclaimer. If the installer

undertakes a risk assessmentof the situation and decides that it is not necessary to bring the existingelement of the installation up to the current standard, then a certificatestating that the installation complies with BS 7671:2008 cannot be issued asthe installation clearly does not comply with the 17th Edition. Listingdepartures on the certificate will only meet the requirements of the Regulationsif the resulting degree of safety of the installation shall be not less thanthat obtained by compliance with the Regulations.

 

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Re-cap.

In the United-Kingdom the following classes of electrical-installations are required to comply with the Statutory-Regulations . :icon_bs:
The Regulations listed represent the principal-legal-requirements . ( Informative )

The IET Wiring-Regulations are not Regulations in the sense of a Government or Ministerial-order having the force of Law .
They are simply-rules or principles .

The Statutory-Regulations with which Wiring-Regulations have most association are : ( Informative)

BS-7671:2008:2011: Appendix - 2 p/292 . Lists the Statutory-Regulations with which certain electrical-installations are required to comply . Etc