Re-take - Useful Information for 2394 :

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Blast from the past :

Also,the IEE’s " Design participants notes " for the 16thEdition BS-7671: confirms that if an RCD is selected to provide indirectprotection, it is not necessary to undertake the disconnection calculations required for Overcurrent devicesbecause the RCD will always trip within 0.2 seconds

( An RCD will trip in 0.04s , under Earth-fault-conditions ) compared to 0.2 seconds

17[SUP]th[/SUP]Edition : Chapter 41 Directcontact now refers to basicprotection and indirect contact is called fault protection

 

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Re-cap :

( RCD operation for Non-time-delayed ) BS-EN-61008-1 . BS-EN-61009-1 … (Part-1 ) :icon_bs:

Table 41.1. gives the maximum-disconnection-timesfor final circuit(s) Not exceeding 32A , of varying nominal-voltages forming part of an ,installation being ?? TN- or TT- system ( Earthing )

P/57 . 411.4.9. States :
That where an RCD is used to meet therequirements of 411.3.2.2. To providethe required disconnection time , the maximum values ofearth-fault-loop-impedance in Table – 41.5 may be applied

The maximum permissible earth-fault-loop-impedance ( Zs ) to ensure ( RCD operation for Non-time-delayed ) ◄ RCDs protectingfinal-circuit(s) Notexceeding 32A are given in Table 41-5 .

Disconnection times required by Table41.1. ( Whether ) Protective-device(s) Fuses , Circuit-breakers , RCDs / RCBOs

2392-10 : in your Understanding .
There is NO requirement toconfirm that the required disconnection time can be ( Achieved ) bytesting the protective-device / (s) .

You are confirming the , Earth-fault-loop-impedance ( of the Protective-circuit ) does not exceed the relevant tabulated maximum earth-fault-loop-impedance , for the Type / Sensitivity of the ( Protective-device)

 

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Old to New : BS /BS-EN :icon_bs:

Operatingtimes of residual current operated devices (RCDs) to satisfy the relevantrequirements for automatic disconnection of supply given in Chapter 41 of BS-7671:

2008.According to Chapter 41, RCDs may provide faultprotection and /or additional protection.

RCDs to BS 4293: 1983 were first introduced into the Wiring Regulations bythe 15th Edition.
The harmonised standard BS EN 61008-1:1995, which superseded BS 4293: 1983, was introduced by Amendment 1 to the 16thEdition (BS 7671: 1992). The same amendment also introduced socket-outletsincorporating RCDs to BS 7288: 1990, portable RCDs to BS 7071: 1992 and RCDsincorporating overcurrent protection to BS EN-61009-1: 1995 (Regulation412-06-02 referred).
Whenthe 17th Edition (BS 7671: 2008) was published, Only BS EN 61008-1 and BS EN61009-1 were still listed (Regulation 411.4.9 refers).

However,this does not preclude the use of RCDs to BS 4293, BS 7288 and BS 7071, whereappropriate, for fault protection and/or additional protection, provided theymeet the relevant operating time requirements.

 

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2392-10 : This is just to referyou to some studying .

P/33 .. Residual-current :
Algebraic sum of the currentsin the live-conductors of a circuit at a point in the electrical-installation .

p/34 .. Residual-current-operated-circuit-breaker ( Without ) integral overcurrent-protection ( RCCB )
p/34 .. Residual-current-operated-circuit-breaker ( With ) integral overcurrent-protection ( RCBO)

4 terminals (2 top, 2 bottom)

( RCCB ) RCDnot RCBO ! BS-4293 RCD

Therefore the circuit connectedto it in theory has no Over-load-protection.

 

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Where an RCDis employed to achieve the disconnection time required by Table 41.1, it isnecessary to satisfy yourselves that the maximum earth-fault-loop-impedance (Zs) Statedfor a , particular sensitivity of RCD inTable 41.5 is not exceeded in the circuit to which they provide-protection .

 

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Re-cap :

BS-EN-61557-6 , has requirements’ forthe following tests to be ( Appliedto RCDs )

□ Non-tripping ( 50% / 0.5 ) test

□ Tripping ( 100% / 1x ) test. C&Gs ... RCD 100mA tested at 100% . 1x BS-EN-300mS . Scenario TT – system .
▲ ( 100mA ... DoNot Test at 5x times rating ) This is what C&Gs want to hear .

Theregulations apply to the Design, Erection and Verification of any electrical-installation

□ 5 I∆n ( 500% ) test

2392-10 ... These two are the ones you will Use □ / Fast trip

 

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2392-10 : Locations containing a Bathor Shower

Regulations – 701.411.3.3. P/199 “Additional-protection “

Shall be provided for all ( Low-voltage-circuits of the location ) by the use of one or more having the ,characteristics specified in , Regulation 415.1.1. P/66

Note : also regulation 314.1. (iv) 531.2.4. concerning avoidance of ,unwanted-tripping Etc .

Regulation – 415.1.1. P/66

The use of RCDswith a rated-residual-operating-current ( I∆n ) not exceeding 30mA & an operating time not exceeding 40mS ata residual-current 5x I∆n is recognised in A.C. systems as additional-protection in the eventof failure of the provision for basic-protection and / or the provision for fault-protection or careless by Users .

 

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2392-10: Domestic – installations

Note : BS-7671: definition of ( Wiring-system )
Does not include lights, but in mostcases the opening made for lighting would be larger and more onerous than openings created for cables.

BS-7671:2004:2008: 2011 : definition of ( Wiring-system ) P/36
An assembly made upof Cables or busbars and parts which secure and, ifnecessary, enclose the cable or busbars .

 

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2392:10 . Designer(s) Installer(s) , first of all you have to decide what you are trying to Achieve & Why.
The O.S.G. section3 . P/25 Guidance :

The requireddisconnection times for TT – systems can ( except in most exceptional circumstances ) Only be achieved byprotecting every-circuit with an RCD .

Electrode-résistance inTT – system(s) 411.5.3. P/57
The Regulations requirethat the earth-résistance at the electrode ( Ra or Zs ) be as low as practicable . Table – 41.5.

States that: 41.5. specifies a maximum-résistance required for a ( 30mA RCD ) to comply is 1.667Ω *
Note 2 : * The résistanceof the installation earth-electrode should be as low as practicable .

Note 2 : A valueexceeding 200Ω may not be stable .
RCD / 30mA earth-current would trip the device within the required ( 0.2s ) conditions comply with 411.5.3.

Fault disconnectiontimes for, TN – TT – systems
BS-7671:2011: specify the requirements forAutomatic-Disconnection of Supply . byprotective-device(s) circuit-breaker(s)of a fault occurring .

BS-7671:2011: disconnection time ( fault’s Occurring )
BS-7671: have statedthe facts . Type of Earthing-systems ?? You , decidewhat you are trying to Achieve & Why.

P/53 , Regulation 41.1. “ Stipulates “ Maximum-disconnection-times

Typeof Earthing-systems
Circuits rated , 32A or less , TN – installation(s) must disconnect within ( 0.4s ) 400mS
Circuits rated , over 32A , TN – installation(s) must disconnect within ( 5s )
Circuits rated , 32A or less , TT – installation(s) must disconnect within ( 0.2s ) 200mS
Circuits rated , over 32A , TT – installation(s) must disconnect within ( 1.0s )

2392-10 : Where does BS-7671:2011: “ Start “
Metal-clad or Plastic all insulated consumer-unit ? What makes thedifference in the eyes of BS-7671:2011 & O.S.G.
Re-cap : 2392-10 : P/29 / O.S.G. The Enclosures of RCDs
Or consumer-units incorporating RCDs in TT – installation(s) should have an ( All-insulated or Class-11 construction oradditional-precautions )
Out of curiosity, Whydoes an RCD allow for a ( Zs of 1667Ω ) P/57 / Table 41.5.

[ I = V/R , R = V/R , 50V maximum-touch-voltage ] / 0.03 ( 30mA ) = 1667Ω :
50V ÷ 30mA = 1.666666667Ω [ round – up to 1667Ω ]
[ 30mA ÷ 1000 = 0.03A]

O.S.G. P/23, ( Protection)
Firstly : Type of protective-devices
The consumer-unit ( or distribution-board ) contains devices for the ( Protection) of distribution-circuits & final-circuits against .
• Overload .
• Short-circuit .
• Earth-fault .

2392-10 : Circuit-breaker & RCBOs don’t stop at , BS-EN.

Stillout there . ( Overload-protection ) BS-3871, O.S.G. P/23
Appx 3 , 533.1. Overload-protection will be provided by the ( Use) of any of the following devices .
Fuses to BS-88-2 , BS-88-3 , BS-88-6 , BS-1361 & BS-3036 .
Under the 16[SUP]th[/SUP] Edition they where called this , Miniature – circuit - breakers to BS-3871-1 types ( 1 , 2 , & 3 )
Circuit-breaker(s) to BS-EN-60898 types , B , C , & D .
Residual-current-circuit-breaker(s) ( With ) integral-overcurrent-protection ,RCBOs, to BS-EN-61009-1

 

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Any & Allsuch liability is disclaimed .

GN-3: All parties must rely upon their ownskill & judgement when making use of them . ( Use as a guide / Guidance Only )
O.S.G.: All parties must rely upon their own skill & judgement when making use ofthem . ( Use as a guide / Guidance Only)

P/25 Competent-person:
A person who possessessufficient technical-knowledge, relevant practical skills & experience forthe nature of the electrical-work undertaken & is able at all times toprevent danger & , where appropriate, injury to him / herself & others .

BS-7671:2011: All parties must rely upon their own skill & judgement whenmaking use of them .

2392-10 & any Electrician takes responsibilityfor there OwnAction . ( in Our case here Moral-responsibility )

 

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Operation of the Test-button . The Why’s

Tripping of the RCD in response to operation of the ( Test-button ) does NOTverify that the RCD will provide protection “ Additional-protection “

“ Verification “ 2392-10

P/36 , All measures by means of which compliance of the electrical installation withthe relevant requirements of BS-7671:are checked :
Inspection .
Testing . Verification of the ability ofthe RCD , to provide-protection can only be ( Assured ) by Testing :icon_bs:
Certification.

 

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RCDs - Testing can be done from any point of the circuit ( e.g. socket-outlet ) or at the outgoing-terminals of the RCD itself.
Prospective-fault-current. 2392-10 .
612.11. ... ( PFC ) is a generic term .

Either :
( PSCC )prospective-short-circuit-current .
( PEFC ) prospective-earth-fault-current.

 

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Some facts 2392-10 . RCD - Tests: :svengo:

Where RCDs ( form ) part of the installation,
Whether , they are for Fault-protection of Additional-protection or both ,

The requirements’ of Regulation(s) 612.8.1. & 612.10.respectively that such devices must be Tested .

This test is in ( Addition ) to the test carried out bythe use of the manual-test-button incorporatedwithin the RCD .

 

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( half-cycles 0°& 180° ) ◄ 2392-10. 2394 . relying on the Megger on Auto . Your marks are costing you money. Yeah Pass or Fail .

GN-3 . P/58 . Operation & functional-testing of RCDs :rant:

The operating times of RCDs are required to be ( Tested) in the following circumstances

612.8.1. ► where they are relied on for disconnection for compliancewith Chapter - 41
612.10. ► where they are installed as additional-protection asspecified in Chapter - 41

Where RCDs areinstalled with circuit-breakers and the circuit has the characteristics to satisfy Chapter – 41without the RCD, then testing of the RCD is not essential unless it is specified for , Additional-protection .

C&Gs . 2392-10 & 2394 . on Exams .

Operation of RCD
411.4.5. ◄◄◄
for each of the ( Tests ) readings should be taken on ( Both positive & negative half-cycles ) and the longer operating-time recorded . ( mS) ( half-cycles 0°& 180° ) ◄

Do we have anEarth ??
► Prior to these RCDs - tests it is essential ,for ( Safety-reasons ) thatthe earth-loop-impedance is tested tocheck the requirement’s have been met.

2392-10 / 2394 . You are :
Verifying protection by automatic supply disconnection

GN-3. P/59 Additional-protection 415.1.
Where an RCD with arated-residual-operating-current, I∆n not exceeding 30mA is used to provide Additional-protection inthe event of failure of basic-protectionand / or the provision forfault-protection or carelessness byusers, the operating time of the device must not exceed 40mS when subjected toa test-current of ( 5x I∆n ) the maximumtest time should not exceed 40mS , Etc

415.1.
612.10. Additional-protection
The verification goesthe effectiveness of the measures applied for Additional-protection is fulfilled by ( Visual-inspection )&( Test )
Where RCDs are requiredfor additional-protection,

The effectiveness ofautomatic-disconnection of supply by RCDs shall be verified usingsuitable-test-equipment , according to BS-EN-61557-6 , see Regulation – 612.1.to confirm that the relevant requirements in Chapter 41 are met .

In the eyesof BS-7671:2008/2011:
612.9. Before ( Circuit-loop-impedance ) Earth-fault-loop-impedance .
612.10. After .

Anearth-loop-impedance-test will measure the resistance offered to the flow ofcurrent in the path that a fault current would take from line to protectiveearth. This resistance must be sufficiently low to allow enough current to flowpast to trip the circuit protective device in place, a Circuitbreaker or something else.

Inspection &Testing .
As GN-3 reminds us . The inspector to be fully-versed in the ( Capabilities& Limitations ) of instruments &be aware when a test is likely to createa dangerous-situation . Regulation -610.1. Your testing , not lead to persons or damage to property orequipment during Inspection & Testing .

Even when the circuitbeing tested is ( Faulty )

632.4. Defects or omissions revealed during , inspection & testing of the installationwork covered by the certificate shall be made good before the Certificate isissued .

 

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Check list : Fused-connection-units .
Re-cap . that require Visual-inspection . prior to carryingout Testing . :icon_bs:

Suitably-fused , whereappropriate . 433.1.1. 434.2.

 

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BS-7671:2011; & GN-3 . wouldany of this come up on Exams . ( Everytest has it’s Merits ) :icon_bs:

C&Gs / GN-3,Stipulates that, The installation must remain isolatedfrom the ( Supply ) until alltesting has been completed & the earth-electrode connection-reinstated .
C&Gs / GN-3,Stipulates that, This disconnection will ensure that thetest-current Only passes through the, earth-electrode and not through any ( Parallel-paths )

( Where-required )
Re-cap : 612.7. Earth-electrode-résistance.
BS-7671: Stipulatesthat where, earth-electrodes are usedthey should be tested. BS-7671: Electrode-resistance to Earth shall be measured
If the electrode under test forms part of the earth-return for a TT – system in conjunction with an RCD, GN-3 describes the following method(s) .

• Disconnect theinstallation-protective-equipotential-bonding ( equipotential / equal bonding ) from the earth-electrode to ensurethat the test current passes only through the earth-electrode .
• Switch off the consumer’s unit to isolate theinstallation
• Using a Earth-loop-impedance-tester, testbetween the incoming line-conductor and the earth-electrode . BS-EN-61557-3 Instruments conforming .
• Reconnect : theprotective-bonding-conductor(s) when the test is completed .

Record the results on a, Schedule of test-results , accordingto Appendix - 6 , BS-7671:
GN-3 : stipulates that, that an acceptable value for the measurement of the earth-electrode-résistance, would be less that 200Ω .
BS-7671:2011: P/57 . Table 41.5 . Note – 2 *: The résistance of the installationearth-electrode should be as low as practicable. A value exceeding 200Ω may not be stable. Refer toregulation 542.2.4. The type & embedded depth of an earth-electrode . Etc

Supply Connected .
Testing earth-fault-loop-impedance :

Your object of this test is to ( Verify) that the impedance of the whole ( earth-fault-current-loop ) islow enough to allow the overcurrent-protective-device to operate within the disconnection timerequired Stated in BS-7671:2011: in our case here Table 41.3. RCBO / Circuit-breakers .

P/36 . Verification : All measures by means of which compliance of the electrical-installationwith the relevant requirements of BS-7671:are checked .
Comprising . Inspection , Testing & Certification .

“ Competent-person “

612.9. Earth-fault-loop-impedance . ( 2392-10 , Circuit-loop-impedance )
Where protective-measuresare used, which require knowledge of earth-fault-loop-impedance, the relevant-impedancesshall be measured .

GN-3 . Re-cap . Protection by automatic-disconnection of supply . P/51.
The effectiveness of measures for fault-protectionby ( ADS ) can be verified for installation(s) with a TN – system by :

• Measurement of earth-fault-loop-impedance .
2392-10 , Reason :- youhave confirmed that you have an Earth before testing your RCDs / RCBOs
• Confirmation by visual-inspection that , overcurrent-device have suitableshort-time or instantaneous tripping setting forcircuit-breakers,
• where RCDs are employed, testing to confirm that thedisconnection-times of Chapter 41 . of BS-7671:can be met .

RCDs :- Residual - dual / Line & Neutral-conductor(s) Two / dual in Balance :rant:

 

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( T ) . One of the most important regulations - 632.4. P/196 . Defects or omissions
Revealed during inspection & testing of the installationwork covered by the Certificate shall be made good before the Certificate isissued . :icon_bs:

Periodic Inspection ( Electrical-installation-condition-report ) EICR .

P/195 . 621.3. Precautions shall be taken to ensure that the periodic-inspection &testing shall not cause danger to persons or livestock & shall not causedamage to property and equipment even ( if the circuitis defective )

• Measuring-instruments & Monitoring-equipment and methods shall bechosen in accordance with relevant-parts of BS-EN-61557. If other measuring-equipment is used, itshall provide no less degree of performance & safety .

Measuring-instruments& monitoring equipment and methods shall be chosen in accordance withrelevant-parts of BS-7671:2011: plus –GN-3

P/195 . 621.4. Theextent and results of the periodic-inspection & testing of an installation,or any part of an installation, ( shallbe recorded )

P/195 . 621.5.Periodic-inspection & testing shall be undertaken by a , Competent-person.

631.2. Upon completion of the periodic-inspection& testing of an ( Existing-installation) an Electrical-installation-condition-report , based on the model given inAppendix – 6, shall be provided .

- such documentation shall include details of the extent of the installation& limitations of the inspection & testing covered by the Report . together with records of inspection, theresults of testing and a recommendation for the interval until the , next periodic-inspection .

P/196 . 634.1. Following the periodic-inspection& testing described in Chapter -62.
An Electrical-installation-condition-report,together with schedules of inspection& schedules of test-results, shall be given by the person carrying out theinspection, or a person authorized to act on their behalf, to the personordering the inspection. Etc . refer to.

P/196. 634.2. Any damage, deterioration, defects,dangerous-conditions and non-compliance with the requirements of theregulations, which may give rise to danger, together with any significant-limitations of theinspection and testing, including their reasons, shall be recorded .

 

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2392-10 : Circuit-breaker(s) - circuit-protection .
Tripping-characteristics & therefore circuit-protection are set by the installer.

 

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2392-10 . Installing : Overcurrent-protective-device(s)

Fault-protection .P/53.
411.3.2.2. Overcurrent-protection-device , providingcircuits Not exceeding 32A . Shall havea disconnection-time not exceeding , 0.4s . Table 41.1

 

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2392-10 : basics .

Testing for Continuityof protective-conductor(s) 612.2.1.

to ensure that thecircuit-protective-conductors, ( CPCs ) is correctly connected, as the Regulation specifies . when testinghas a total-résistance which is low-enoughto permit the overcurrent-protective-device to operate . with the disconnection time requirements of Regulation - 411.4.5.

Earth-fault occur . RCDs for additional-protection

 

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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.

 

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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.