Re-take - Useful Information for 2394 :

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2392-10 / 2394. :icon_bs:

134: Erection & Initial-verification of electrical-installation(s)

134.2.1. P/22. Initial-verification .

During erection and oncompletion of an Installation or an Additionor Alteration to an installation & before it is put into service

Appropriate , Inspection & Testing shall be carried out by Competent-person , to verify that the requirements of this standard have been met . ( & Appropriatecertification to be issued )

135. Periodic Inspection & Testing . ( Recommendation for subsequent periodic-inspection & testing required)
135.1. it is recommended that ( Every electrical-installation ) is subjectedto periodic-inspection & testing, Etc

Dealing with : P/21.
134.1.1. Good workmanship & proper-materials .
134.1.2. Characteristics of equipment not to be impaired during erection of Installation(s)
( T ) 124.1.3. Conductor(s) to be identified . ( Polarity)
134.1.4. Every electrical-joint and connection shall beof proper, construction as regards conductance, insulation, mechanical-strengthand protection
134.1.5. Electrical-equipment shall be installed insuch a manner that the ( design-temperatures not to be exceeded )
134.1.7. Suitable-warning-signs & / or notices tobe provided where necessary for safety-purposes.

2392-10 : For :- Electrical-equipment to be installedin accordance with the ( Instructions provided by the manufacture )
134.1.2. Require that equipment must Not be impaired by the ( Installation-process )

Re-cap : P/33.
Reporting :Communicating the results of,periodic-inspection & testing , of an electrical-installation , to theperson ordering the work .

2392/10 : Skilled-person. P/34
A person with , technical-knowledge or sufficient-experience to enable him / her to avoid dangers , which electricity may-create .

Verification: P/36.
All measures by meansof which compliance of the electrical-installation with the relevantrequirements of BS-7671: are checked ,
Comprising , Inspection, Testing & Certification . Etc

Appendix 15 ( Informative ) P/425.
2392-10 : Regulation - 433.1.103.

The Regulation(s) havestated the facts . :vanish:
The load-current in anypart of the circuit should be unlikely to exceed for long-periods the ,current-carrying-capacity of the cable .
Re-cap . 433.1.103.refers , Thiscan generally be achieved by:
i) locating-socket-outlets to provide reasonable sharing of the loadaround the ( Ring )
ii) Not-supplying,immersion-heater(s) , loads of asimilar-profile from the , ring-circuit.
iv) taking-account of the total-floor area being served , ( Historically , a limitof 100m[SUP]2 [/SUP] has been adopted )

iii) connecting-cookers, ovens and hobs with a ( rated-power-exceeding 2kW) ontheir own-dedicated radial-circuit .

 

[Robert Wesson]

made a mock test if it helps 2394


[url]http://2394.robertwesson.co.uk/



[/URL]

 

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Robert Wesson , anything to help Electricians . most appreciated . Amber . :icon14:

 

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This is Notcriticism just some Facts.

If we take the time to Open any Books , It’s right in front of Us . Yeah. :icon_bs:

GN-3 Inspection & Testing.

is an essentialguide and leading reference manual on this important subject. The Guide has beenrevised to align with the BS-7671 (------ Wiring Regulations) 17[SUP]th[/SUP]-Edition-Amendment No 1, the National - Standard to which all domestic and industrialwiring Must -Conform.

Contents : Initial-verification, Periodic-inspection& testing, Test-instruments and forms.

Polarity-Testing . GN-3.. P/47
612.6. The polarityof all circuits must be verified beforeconnection to the ( Supply ) with either an ( Ohmmeter or the continuity-range of an Insulation & Continuity-tester)

As GN-3 have stated the Facts . Instrument: Use a low-resistance-ohmmeter, forthese-test. Etc:
As the Wording means : Guidance-Only

As GN-3.. reminds Us , Alternatively, polarity can be verified byvisually checking ( Core-colours at terminations ) thus verifying the installer’s connection(s) this will come up in Exams .

2392-10 / 2394 . As GN-3.. reminds Us , The continuity-test, & ring-continuity-test ( May-confirm-polarity )

Which of the following is themost suitable instrument to conduct a polarity test ?
a) a high resistance ohmmeter.
b) a bell set.
c) an insulation resistance tester.
d) a low resistance ohmmeter.

GN-3 . P/82 : Low-résistance-ohmmeter(s)
The instrument used for , low-résistance-testsmay be either a specialised low-resistance-ohmmeter
Or
Thecontinuity-range of an insulation & continuity-tester .

It is recommended that low-resistance ohmmeters used for continuity measurements should have a no-loadvoltage and a short-circuit current of ?
a) Voltage between 4V and 24V; short-circuitcurrent of 200mA. ( 612.2.1. ) GN-3 -
b) Voltage between 0V and 24V; short-circuitcurrent of 100mA.
c) Voltage between 4V and 20V; short-circuitcurrent of 1mA.
d) Voltage between 0V and 20V; short-circuitcurrent of 1mA.

-&-s do Something for a Reason !! ( Competent Person )

GN-3 /39 Insulation-résistance . Re-cap . ( 2 )
Note : Pilot or indicator-lamps, aredisconnected from circuits to avoid an , inaccurate-test-value being obtained .

GN-3 /76 . 2392-10 / 2394. Functional-tests, Functional-testing . ( 612.13.2.)
Functional-tests of ( Circuit-breaker(s) Isolators’ & Switching-devices .

 

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Understand therequirements for initial verification of electrical installations
Assessment criteria

2.1. state the purpose of the Initial Verificationof electrical installations
2.2. state the requirements of theinitial verification
2.3. identify the relevant documentsassociated with the inspection, testing and commissioning of an electricalinstallation
2.4. specify the information that isrequired by the inspector to conduct the initial verification of an electricalinstallation

Regulation have stated thefacts .

Certification & Reporting .
631.1. P/195
Upon completion of the ( Verification of a new Installation) Or changes to anexisting-installation, an EIC , shall be provided, Such documentation shallinclude details of the extent of the installation covered by the Certificate,
Together with a record ofthe inspection, the results of testing and a recommendation for the interval untilthe , first-periodic-inspection .

Initialverification procedures :
Weinspect and commission material after the completion of work for three key reasonsto ensure:
□ Compliance with BS7671
□ Compliance with theproject specification (commissioning)
□ That it is safe to use. ◄ . The most important requirement .BS-7671:2011.

Compliance with BS 7671:2011:
BS 7671 Part 6 states that every electrical installation shall,either during construction, on completion, or both, be inspected and tested toverify, so far as is reasonably practicable, that the requirements of theRegulations have been met.

In carrying out such inspection and test procedures, precautionsmust be taken to ensure no danger is caused to any person or livestock and toavoid damage to property and installed equipment

BS-7671:2011: requiresthat the following information be provided to the person carrying out theinspection and test of an installation:

□ the maximum demand ofthe installation expressed in amperes per phase
□ the number and type oflive conductors at the point of supply
□ The type of earthingarrangements used by the installation, including details of ( Equipotentialbonding arrangements ) making me Equal
□ the type andcomposition of circuits, including points of utilisation, number and size ofconductors and types of cable installed ( this should also include details of the‘ reference installation method ’ used )
□ the location anddescription of ( Protective-devices )- ( fuses, Circuit breakers ,RCDs , RCBOs etc.)
□ details of the methodselected to prevent danger from shock in the event of an earth fault, e.g.earthed equipotential bonding and automatic disconnection of supply
□ the presence of anysensitive electronic devices. ... 612.3.3. refer - Note Additional-precaution’s . Etc

It is important to remember that periodic inspection and testingmust be carried out on installations to ensure that the installation has notdeteriorated and still meets all requirements. Tests will also need to becarried out in the event of minor alterations or additions being made toexisting installations.

Once the installation is complete, we need to test it againstthe original specification for the work. This is in order to check that the finishedinstallation matches the requirements laid out by the customer and is fit foruse in the environment where it will be used. The tasks involved in checking compliancewith project specification are as follows.

Pre-commissioning - this involves a fullinspection of the installation and the carrying out of all tests requiredbefore the installation is energised ( continuity,polarity and insulation resistance ).

Commissioning - includes all tests whichrequire power to be available, e.g. the measurement of the earth-fault-loop-impedance and functional-testingof residual-current-devices (RCDs).

As commissioning involves the initial energising of aninstallation, this task has to be carried out in a controlled manner with theknowledge of everyone involved. This means that all other persons working onsite at the time of the energising must be taken to prevent danger.

The commissioning process is intended to confirm that theinstallation complies with the designer’s requirements. As such, commissioningincludes the functional testing of all equipment, isolation, switching,protective devices and circuit arrangements.

 

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Safe to use : As a Competent-person .

The final act of the commissioning process is to ensure the safeand correct operation of all circuits and equipment which have been installed,and that the customer’s requirements have been met. This will also confirm thatthe installation works and, more importantly, will work under fault conditions;after all, it is under fault conditions that lives and property will be atrisk.
The testing of electrical installations can cause some degree ofdanger; it is the responsibility of the person carrying out the tests to ensurethe safety of themselves and others. Healthand Safety Executive Guidance Note GS38 (Electrical test equipment for use by electricians ) details relevant safetyprocedures and should be observed in full.

When using test instruments the following points will help toachieve a safe working environment.

The person carrying out the tests must have a thoroughunderstanding of the equipment being used and its rating.

The person carrying out the tests should ensure that allinstruments being used conform to the appropriate British Standard, i.e. BS-EN-61010or older instruments manufactured to BS-5458 (provided these are in goodcondition and have been recently calibrated).

 

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Competenceof the inspector : Exams , Writing

considerationwhen carrying out inspection and tests is the competence of the inspector. Anyperson undertaking these duties must be skilled and experienced and have sufficientknowledge of the type of installation. It is the responsibility of the inspectorto:

- ensure no danger occursto people, property and livestock
- confirm that test andinspection results comply with the requirements of BS-7671 and the designer’s requirements
- express an opinion as to the condition of theinstallation and recommend remedial works
- make immediaterecommendations, in the event of a dangerous situation, to the client toisolate the defective part.

Operatingdevices
It is not an adequate precaution simply to isolate a circuitelectrically before commencing work on it. It is vital to ensure that once a circuit oritem of electrical equipment has been isolated, it cannot inadvertently beswitched back on. ( Locking-OFF )

method of providing full electrical and mechanical isolation isto lock off the device (or consumer-unit, distribution board containing the device) with a padlock

A skilled person should bethe only one allowed to carry out this or similar responsible tasks concerningthe electrical installation wiring.

 

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Test-procedures 612.2.1.

Continuity of protective-conductors and equipotential-bonding-conductors

Exams, -&-s would like to here this first . Where the installation can be safely isolated from the supply,

(CPC ) Circuit-protective-conductors andequipotential-bonding-conductors can be disconnected from the main earthing terminal in order to verify their continuity.

Wherethe installation cannot be isolated from the supply, the circuit protective conductorsand the equipotential bonding conductors must not be disconnected from the mainearthing terminal,

Under –fault-conditions , extraneous metalwork could becomelive.

Underthese circumstances a combination of inspection,continuity testing and earth loop impedance testing should establish theintegrity of the circuit protective conductors.

 

[amberleaf]

It’s all in the wording . 2394

Exams, -&-s would like to here this first . Insulation-resistance-tests canonly be carried out where it is possible to safely isolate the supply.

 

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Some Extracts , HSE – Guidance .

No circuit should bemade available for use until it has been fully-completed & inspected & tested in accordance with BS-7671: :icon_bs:
Including checks toensure that earthing-arrangements & protective-conductors ( includingmain-protective-bonding-conductors ) are in place : &

Anycircuit that is ( Incompleteor has yet to be fully inspected & tested ) must remainsecurely-isolated at the , Supply-end .

 

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2392-10 .

The most important, & overlooked, aspect of safety in electrical-testing is that of a , skill of theoperator-undertaking the testing .

Residual-current-device ,test-instrument

Regulation(s) 612.8.1. & 612.10 require the use of an RCD-test-instrument toBS-EN-61557-6 , to test the operation RCDs used for fault-protection &additional-protection . respectively .

Sources of information

Initial-verification isintended to confirm that the installation complies with the designer’srequirements and has been constructed, inspected and tested in accordance with BS-7671. In your case here. 2392-10. Installer / Designer .

Functional 612.13. : & 612.13.1. 612.13.2.

Activities to becarried out: Etc.

All RCDs to be checked both by , Testinstrument and by Test button
All Manually-operated-circuit-breakers tobe operated to verify they open and close correctly.

Operation of circuit-breakers . ( Don’t overlookCircuit-breaker(s) because of RCDs / RCBOs )

All circuit-breakersshould be inspected for visible signs of damage or damage caused by Overheating.
Each circuit-breaker should be manually operated to ensure that the device opens and closescorrectly

 

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IET-Guidance-Note 3 . 2.1 p/15 . 2392-10 / 2394 .
Chapter -2 “ Pupose of Initial-verification ”
610.1. Initial-verification is carried out on a , New-installation before it is put into service .

2.7. P/31 . Initial-testing .
The test-methodsdescribed in this section are recommended to be used for verification. In this respect , GuidanceNote-3 is cited in Regulatrion 612.1
This does not rule out the use of othertest-methods provided they give valid-results .

610. Testing
610.1. General:
The tests Regulations 612.2. to 13 , where relevant, shall becarried out & the results compared with relevant-criteria .

2.7.1. Test-results.
The test-results must berecorded on the Schedule(s) of Test-results & compared with relevant-criteria.
2.7.4. P/32 The sequence of tests
Initial-testsshould be carried-out in the following , sequence where relevant &practical: Regulation 612.1.

( Wording ) Reg.P/33 . Reporting : Communicating the results of , Periodic-inspection & testing of an electrical-installation tothe person-ordering the work .

Verification : All measures by means of which compliance ofthe electrical-installation with the relevant-requirements of BS-7671:are checked ,
Comprising :

Inspection . “ Visual “
Testing .
Certification .

 

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Which one of thefollowing best describes the operation of a RCD ?

□ Magnetic
□ Thermal
□ Current balance
□ hydraulic

 

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Replacing a consumer-unit in an ( Existing-installation) is an , Addition or Alteration to thatinstallation .
The work must therefore be , Designed ,Erected & Verified , in accordance with the requirements of thecurrent-edition of BS-7671: &must not impair the safety of the , existing-installation
Regulation(s) 110.1.2. ( vi ) 610.4. refer .
P/14 . 110.1.2. additions & alterations to installations& also parts of the , existing-installation affected by an addition &alteration

Initial-Verification .

P/189 . 610.4.
For an addition &alteration to an ( Existing-installation) it shall be verified that the additionor alteration complies with the ,Regulation(s) & does not impair the safety of the ( Existing-installation)

610.5. The verification shall be made bya , Competent-person .
610.6. On completion of the verification, according to , Regulation(s) 610.1 to 5 , a Certificate shall be prepared .
P/36 . Verification .
All measures by means of which compliance of theelectrical-installation , with the relevant requirements of BS-7671: are ( Checked ) comprising inspection , testing , & certification .

Re-cap : P/190 .612.1 General .
The tests of Regulation(s) 612.2. to 6 , whererelevant , shall be carried out in that ( Order ) before the installation is energized .

 

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Guidance Note-3 , is concerned principally with Inspection and Testing
" IET Wiring Regulations( BS-7671:2011: ) 17th Edition ".

Coverage

Initial-verification
Periodic-inspection
Test-instruments.

GN-3 : Which enlarges upon and amplifies the particularrequirements of a part of the 17th Edition Wiring Regulations BS-7671:2011:
Each of these guides GN-3. is extensively cross-referenced to the Regulations

 

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Main-earthing-terminal(MET)

The function of the MET is to , provide a reference point for the installation. :icon_bs:
It consistsof a terminalor bar provided for the connection of protective conductor(s), including main-protective-bonding-conductor(s),& conductors for functional-earthing.

Although the MET is connected to Earth it is seldomat , Zero potential because of the potential-difference caused byleakage and other currents flowing to Earth.

 

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Re-cap : System(s)

TN-S system (Figure 3.8 - 2011)
In a TN-S the Neutraland Protective conductors should be kept separate throughout the system and thesource is solidly earthed.

Commentary on :

A TN-S system has a particulardisadvantage that in the event that the protective conductor becomes opencircuit, there is no indication that a fault has occurred and installations canunknowingly be left without an earth. In the event of an earth fault all of theexposed-conductive-parts within a consumer installation may be raised to ahazardous potential. Earth fault protection devices will not operate as therewill be no flow of current to earth.

TN-Csystem
Ina TN-C system (Figure 2.2 - 2008) the neutraland protective functions should be combined in a single conductor (PEN)throughout the entire system. Multiple connections to earth are recommendedalong the PEN conductor and the source is solidly earthed.

Commentary on :
The need for multiple earth connections is becauseif the neutral becomes open-circuit for any reason, theexposed-conductive-parts will rise to line to earth voltage in the case ofsingle-phase connections and a value up to line to earth voltage in the case ofthree-phase connections, depending on the degree to which the load isunbalanced.

TN-C-Ssystem
Ina TN-C-S system, (Figure 3.9 - 2011) theneutral and protective functions should be combined in a single conductor (PEN)from the source (solidly earthed) up tothe consumers intake. Multiple connections to earth are recommended along thePEN conductor. Within the consumer’s installation the neutral and protectiveconductors should be kept separate.

Commentary on :

The TN-C-S system is also known as a “ protective multiple earthed ” (PME) system.The PEN conductor, which is referred to as a combined neutral and earth (CNE)conductor, is earthed at the source and extremities of the distribution mainsand points in-between; hence the reference to multiple earthing. Multipleearthing of the CNE conductor ensures that if the conductor becomesopen-circuit for any reason, exposed-conductive-parts remain connected toearth; under such conditions the supply voltage between the installation lineand neutral conductors is substantially reduced and consumers will experienceunacceptable voltage variations.

TTinstallation
ATT system (Figure 3.10 - 2011) has a solidly earthed source; theexposed-conductive-parts of the consumer’s installation are earthed through aninstallation earth electrode which is electrically independent of the sourceearth.

Commentary on :
In the TT system the earth fault loop impedance isgenerally high as the fault path includes the earth electrode resistance of thesupply and the earth electrode resistance of the consumer’s installation.

IT System
AnIT system (Figure 2.6 - 2008) has the sourceeither connected to earth through an earthing impedance or is isolated(Insulated) from the earth. All of the exposed-conductive parts of aninstallation are connected to an earth electrode in a similar manner to a TTarrangement.

Commentary on :

Generally an IT system would be chosen in locationssuch as medical centres and mines where the supply has to be maintained even inthe event of a fault, and where the connection with earth is difficult (forexample a mobile generator).

 

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RCBOs. RCD / MCB . Exams . Wording . Yeah

Meansfor removing the supply to the protected circuit ( a circuit breaker element ) when the residual currentexceeds the rated residual operating current of the device.

 

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RCCB differs from an RCBO in that the RCBO will additionallyrespond to overcurrent conditions whereas the RCCB will not respond tosuch conditions.

p/34. RCBO . with integral-overcurrent-protection
p/34. RCCB . without integral-overcurrent-protection

RCD's work by means of the , current balance principle
Thatis, the algebraic sum of all the electric currents meeting at any point in acircuit must be zero,otherwise the circuit will be broken.
AnRCD's circuit is broken when the residual current is between 50% & 100% ofthe rated tripping current, as required by the relevant British Standards.

Principle of Operation
Inan electrical installation, current will flow from the supply to a load andback to the supply. The load can be connected between Line and Neutral on asingle phase installation.

Underperfect conditions, the magnitude of the current flowing to the load will equalthe magnitude of the current returning from the load back to the supply. Anydifference in the current flowing to the load and returning from the load isknown as a residual-current. Under earth fault conditions, a current will flowto earth, giving rise to a residual-operating-current.

Definition P/34.
Residual-operating-current, Residual-current whichcauses the RCD to operate under specified-condition(s)

 

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Electrical contractor has an obligation to ensure that the workhe undertakes to the existing-circuits and the alterations and additions complies with the IET Wiring Regulations. 2011:

P/390 . EIC , should identify the electrical-workthat was carried as “ New “

An Addition or anAlteration , The term New is appropriatewhere the , whole-installation had been installed
The term : “ Addition “ isrelevant if an existing-installation has been modified by the Addition of oneor more new-circuits .
The term : “ Alteration “ is appropriate to where one or moreexiting-circuits have been modified or extended , or items such asconsumer-units

MEIWC , Limited-application

Current-ratings ofconductors, Extracts .

“ if the wires become perceptibly warmed by the ordinary current, it isa proof that they are too small for the work that they have to do and that theyought to be replaced with wires of a larger size ”

Conductors shouldbe sufficient in size for the work which they are called upon to do.