Re-take - Useful Information for 2394 :

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Re-cap:

The is the nearest I canget to Q/As about , Safe-Isolation.

Q) To verify or prove a successful-electrical-isolationyou would use a ? Voltage-indicator
Voltage-indicator
Voltage-proving-unit
Set of GS-38 test-leads
Small-padlock.

Q) To securean electrical-isolation you should use a ? padlock .
Voltage-indicator
Voltage-proving-unit
Set of GS-38 test-leads
padlock .

Q) Where a test-instrument or voltage-indicator is used to prove a supply-dead , thesame-device must be tested to show that it still-works using a ? Voltage-proving-unit
Voltage-indicator
Voltage-proving-unit
Set of GS-38 test-leads
Small-padlock.

Q) To give adequate-protection to theperson carrying-out a safe-isolation-procedure , thetest-instrument must incorporate a ? Set of GS-38 test-leads
Voltage-indicator
Voltage-proving-unit
Set of GS-38 test-leads
padlock.

Q) When connecting single-phase-loads to a three-phase-supply , we must take care to distribute the single-phase-loads equallyacross the three-phases so that each phase carries approximately the same-currents , this is called ? Balancing of theload .

Re-cap: Socket-outlets. 2392-10

Additional - 30mA RCD protection is required for socket-outlets .
Ifused by Ordinary-persons .
And intended for general-use

Regulations - 411.3.1. 415.1.1.

Additional protection for socket-outlets . RCD / Circuit-breaker .

Additional-protection by 30mA RCD is required in ( Addition ) to ( Overcurrent-protection ) for allsocket-outlets to be used by Ordinary-persons and intended for general-use .

For this reason . Additional protection
Is provided in case ( Basic-protection ) or ( Fault-protection-fails ) or if the User of the installation is careless - 415.1.1.

By definition . Ordinary-person : A person who is neither a skilled-person nor an instructed-person .

 

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Q) Continuity of protective-conductors .

Recap -Written exams . 2394

What is you reason for this .
The object of the test is to ensure that every-circuit-protective-conductor is correctly-connected and has avery-low-résistance .

Q) Insulation-résistance - ( IR )

What is you reason for this .
The object of the test is the verify the quality of theinsulation and that the insulation-résistance has a high-value . MΩ

The test is made at the consumer-unit with the supply-disconnected using an insulation-résistance-tester which supplies a voltage of 500V . ( BS-EN-61557-6 )

Q) Part - 6 of the IET - Regulations deals with ?
Protection for safety
Selection and erection of equipment
Special-installations
Inspection & testing .

Q) the electricity-supply to adomestic-consumer is usually protected at the incoming-service-position by a ?
Meter
Double-pole-switch
100A circuit-breaker
100A HBC - fuse . ( BS-88-3 - C )

Q) What action is necessary toproduce a secure-electrical-isolation ? The isolated-supply must be locked-off or secured with a padlock
Isolate the supply and observe that thevoltage-indicator-reads-zero
Find connect a test-device such as a voltage-indicator to the supply
Larger-pieces of equipment may require-isolating at a local-isolator-switch
The isolated-supply must be locked-off or secured with a padlock

 

[amberleaf]

My- point .

The form of protection-provided by the Insulation of Live-parts would be .
Protection against “ direct-contact “

p.23 . Basic-protection: Protection against electric-shock under fault-free-conditions .
Note : for low-voltage installations , systems andequipment . basic-protection generally-corresponds to protection against “ Direct-contact “ that is “ Contact of persons or livestock with Live-parts“

Whywas the name left in BS-7671:2008 “ Direct-contact“
“ Direct-contact“ Deleted by BS-7671:2008: ( see Basic-protection)

It was left in the BS-7671:2008:2011: for a better understanding of the meaning of the : Word “ Direct-contact “

Calculationof earth-fault-loop-impedance : ( Zs )
Themost commonly used protective-measure against ( “ Direct-contact “ Basic-protection) is that of automatic-disconnection of the supply , using the overcurrent-protective-device

Which also provides protection against overload & / or short-circuit-currents for the circuits-concerned .

Residual-current-devices ( RCD ) or combined-devices ( RCBOs ) RCD / Circuit-breaker . ( inExams use the full-name , Not MCB )

Whichever type of device is chosen , it is necessary for the designer to calculate the earth-loop-impedance ( Zs ) of every-circuit in the installation .
Tocheck that these impedances do not exceed the maximum specified in BS-7671:2008:2011: Tables, 41.4. 41.5 . Etc .

The earth-loop-impedance thathas to be considered is that which comprises the impedance of the source , the Line-conductor up to the fault plus the protective-conductor from the fault to the source , Note : that when an RCD or RCBO is used to provide automatic-disconnection of the supply in a TN- system , the calculations of ( Zs ) is normally unnecessary-provided that continuity of the earth-loop hasbeen established .

Regulation: p.55 . look at 411.4.7. / 411.3.2.3. , the values specifiedin Table - 41.3 for the types and ratings of overcurrent-devices listed may be used instead of calculations . 2392-10. your off the hook here . RCBOs or Circuit-breakers .

Where a circuit-breaker is used tosatisfy the requirements of Regulation , Etc. Uo of 230Vand disconnection-time of 0.4s in accordance with Regulation - 411.3.2.2. or 5s in accordance with Regulation - 411.3.2.3. the values specified in Table - 41.3 for the types andratings of overcurrent-devices listed may be used instead of calculations .

Re-cap: 2392-10 . ( RCBOs ) RCD / Circuit-breaker / Overcurrent-protective-device.

You will not get this in your Exams . 2392-10, just an understanding . Yeah .
Theother , reason for calculating the earth-loop-impedances is to check that the circuit-protective-conductors areadequately-protected-thermally .
Thatthey comply with ,adiabatic-equation given inRegulation - 543.1.3. Etc .

BS-7671:1992: + Amd 1:1994 included a regulation that required account to be taken of the increase in temperature and résistance of conductors as a result of the fault-current .

However: this Regulation also allowed a simpler approach to be taken under-some-conditions , for thedevice listed in Appendix - 3 of BS-7671: 1994 , the requirement was deemed to be satisfied if the circuit-loop-impedance met the required when the conductor(s) are at there normal-operating-temperature .

Fuses to BS-88-3 - C . up to 100A . p.56. Old - BS-1361
Semi-enclosed-fuses to BS-3036 to 100A .p.56 .
Fuses to BS-88- part 2 .& Part -6 up to 100A . p.56 .
Type B . C , D , circuit-breakers , BS-EN-60898 , & RCBOS to BS-EN-61009-1 up to 125A . p.56

circuit-loop-impedance -1994 , ( Zs ) The word circuit-loop-impedance is not used 2011: Earth-fault-loop-impedance. all it does is define it a bit better . Yeah . use the full title in exams .

 

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GN-3: p.39
The purpose of the insulation-résistance-test is to verify that the insulation ofconductors-provides adequate-insulation , is not damaged and thatlive-conductors or protective-conductors are ( Notshort-circuited )

Operation of two-wayand intermediate light-switch s -&-s

GN-3. p.40 / 41 .
Insulation-résistance-test of a whole-consumer-unit . ( Lamps removed for test ) Open-circuit

For circuits containing two-way-switching or two-way and intermediate-switching ,the switches must be operated oneat a time and the circuitssubjected to additional-insulation-résistance-test in these-configurations .

GN-3. p.41 .
Insulation-résistance-test of a final-circuit . ( Lamps removed for test )

Operation of two-wayand intermediate light-switch s -&-s

For circuits containing two-way-switching or two-way and intermediate-switching ,the switches must be operated oneat a time and the circuitssubjected to additional-insulation-résistance-test in these-configurations .

 

[Knobhead]

Spam.

Pitty you can't spell, a credit to you're company.

To confuse everyone, the post I was refering to has been deleted. NOT AL's posts.

 

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O.S.G.p96 .

Re-cap,

For an installation-operating at 400/ 230V , although an insulation-résistance-value of only 1MΩ complies with BS-7671 :

Where.

The insulation-résistance-measured is less than 2MΩ the possibility of a latent-defect-exists .

In these circumstances , each-circuit should then be tested separately .

2394 : Keep in mind written-exams . :gettree: :17:

 

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O.S.G.p87 . 2392-10 , just starting out on Inspection & Testing . Inspection meaning - Visual is our first line of defence .

One of the most important Regulations in exams , 612.1.
If any test indicates a failure to comply , that test and any preceding-test , theresults of which may have been influenced by the fault-indicated , shall berepeated after the fault has been rectified .

O.S.G. 9.3. Testing .
Testing must include relevant-tests from the following-checklist

O.S.G. 9.3.1. Testing checklist . ◄

Insulation-reading:
Test-instrument , Readings with leads . Open-circuit - > 999MΩ .

Q) if there is no British-Standard then the insulation-résistance should not be less than 1MΩ .

 

[amberleaf]

Leaning - Curve . Only. Old-Notes 2008 . :icon_bs:

From the information given determine ,

The value of the insulation-résistance-measured taken and the requirements of BS-7671: are satisfied . Your-Call . Yeah

1/Rt = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5

1/Rt = 1/6 + 1/3 + 1/4 + 1/12 + 1/6

Find the lowest-common-denominator i.e. - 12

= 2 + 4 + 3 + 1 + 2 - 12 .

1/Rt = 12 / 12

Therefore : Rt/1 = 12 / 12 = 1MΩ .

Re-cap . Reminder - Guidance-Note - 3 .

Although the requirements of BS-7671: appear to have been satisfied , GN-3 refers to the possibility of a [ Latent-Defect ] existing within the installation . the circuits’ should be tested individually and a minimum-insulation-résistance of 2M is recommended .

As the measurement taken for all of the circuits are above 2MΩ then no investigation would be required .

 

[amberleaf]

Leaning - Curve . Only. Old-Notes 2008 . :icon_bs:

From the information given determine ,

The value of the insulation-résistance-measured taken and the requirements of BS-7671: are satisfied .

1/Rt = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5 + 1/R6

1/Rt = 1/120 + 1/30 + 1/40 + 1/12 + 1/60 + 1/10

Find the lowest-common-denominator i.e. - 120

= 1 + 4 + 3 + 10 + 2 - 12 - + 12 - 120

1/Rt = 32 / 120

Therefore : Rt/1 = 120 / 32 = 3.75MΩ .

 

[amberleaf]

Electricians , Do I Mixor Match ??

SafeSection of Devices for Installation in Assemblies . August - 2011:

Awarning against the practice of installing devices ( E.g. RCBOs , Circuit-breakers ) of one-manufacturer into assemblies ( E.g. consumer-units . Distribution-boards ) of another-manufacturer . there is evidence that some installers aremixing-products , oftenwithout fully understanding the potential-safety-implications .

Assembliessuch as consumer-units , Distribution-boards and panelboards are tested with specific-devices installed , these devicesare more often than not from the same- manufacturer as the enclosure , testingand certification is undertaken to BS-EN-60439 . formerlyBS-5486 Although BS-5486 is now obsolete there are manyexisting-installations with assemblies complying with this standard and the issues of mixing-different-manufacturer’s devices equally apply , particularly where older-devices maybe difficult to source .

Inall cases , installing-devices other than those declared by the assembly-manufacturer invalidates any testing / certification andwarranty .

BS-7671uts specific-responsibility on the installer . Regulation - 510.3 . requires that the installer takes into account the manufacturer’s-instructions . it is therefore theresponsibility of the installer who intends to , mix-different- manufacturer’s-devices/ components . in an assembly , to undertake appropriate-testingand ensure-conformity with BS-EN-60439 . if this is not done then there is aprobability that , in the event of death . injury . fire or other-damage , the installer would be accountable under , Health & Safety - legislation .

Althoughdevices may appear similar , the dimensions . technical-performance andterminations are not necessarily-compatible .

Distributor and Wholesalerresponsibilities :

A distributor and wholesaler also has aresponsibility under the , general-product-safety-regulations to act “ withdue care “
Distributorand wholesaler should be able to substantiate any advice related to ,interchangeably of devices in assemblies , if the installer acts on a distributor’s - advice and information , andin doing so produces anon-compliant-assembly , then both the distributor and installer may be liable forany-consequences .

 

[amberleaf]

Circuit-breakers to BS-EN-60898 &RCBOs to BS-EN-61009-1 in non-preferred-current-ratings

Circuit-breakersto BS-EN-60898
RCBOsto BS-EN-61009-1 are sometimes encountered that have a rated-current other than thepreferred-values [ 3A , 6A , 10A ] listed in Table - 41.3. of BS-7671:2008:2011:

Themaximum-value of ( Zs ) for such a device , at a nominal-voltageof [ Uo - 230V ] can be found from the right-hand-columnof Table - 41.3. of BS-7671:2011:
Table- 41.3 , right gives therelevant-information .

Type - B circuit-breaker . having arated-current ( In ) of 8A ( or the overcurrent-characteristic of an8A Type - B RCBO ) the maximum-value of ( Zs )
at 230Vis 46 / In , = 46 / 8 = 5.75Ω .

Maximum( Zs ) for circuit-breakers to BS-EN-60898 and the overcurrent-characteristic of RCBOs to BS-EN-61009-1for instantaneous-operation giving compliance with the , 0.4 & 5 seconds ,disconnection-times at nominal-voltage [Uo - 230V ]

Table- 41.3.

Type- B - ( Zs ) Ohms for devices ofrated-current ( In ) 46/In .
Type- C - ( Zs ) Ohms for devices ofrated-current ( In ) 23/In.
Type- D - ( Zs ) Ohms for devices ofrated-current ( In ) 11.5/In.

Obsolete-Circuit-Breakers :
Maximum-valuesof ( Zs ) for circuit-breakers for which thisinformation is no longer given in BS-7671: can be obtained either from the edition of BS-7671: that was current when the deviceswere readily-available , or by reference to the manufacture’s - data .

Alternatively, for MCBs to BS-3871: Table - 2 , can be used to find the maximum-value of ( Zs ) at a nominal-voltage of [ Uo - 230V ]

For a Type- 2 circuit-breaker to BS-3871: having a rated-current ( In ) of 30A , the maximum-value of (Zs ) at 230V is [ 32.8 / In = 32.86/ 30 = 1.1Ω ]

Maximum( Zs ) for circuit-breakers toBS-3871: for instantaneous-operationgiving compliance with the , 0.4 & 5 seconds , disconnection-times at anominal-voltage of [ Uo - 230V ]

Type( Zs )
Type- 1 . Ohms - for device of rated-current- ( In ) 57.5/In
Type- 2 . Ohms - for device of rated-current- ( In ) 32.86/In
Type- 3 . Ohms - for device of rated-current- ( In ) 23/In
Type- 4 . Ohms - for device of rated-current- ( In ) 4.6/In

Type- B - ( Zs ) Ohms for devices of rated-current ( In ) 46/In .
Type- C - ( Zs ) Ohms for devices of rated-current ( In ) 23/In .
Type- D - ( Zs ) Ohms for devices of rated-current ( In ) 11.5/In .

Obsolete-fuses :
Maximum-valuesof ( Zs ) for fuses for which this information is no longer given in BS-7671: can be obtained either from the editionof BS-7671: that was current when the deviceswere readily-available , or by reference to the manufacture’s - data .

After 31 - December 2011 : one of these approaches is necessary forfuses to BS-88-2.2. : BS-88-6 : and BS-3871 : as data for them is notincluded in , BS-7671:2008:incorporating Amendment - 1 . 2011:

Overcurrent-protective-devices generally :
Forany type and rated-current of a fuse or overcurrent-circuit-breaker , includingall those mentioned above , the maximum-value of ( Zs ) can be found using the , formula given in Appendix - 3 of BS-7671: Where :- Zs = Uo /Ia .

Uo- is the nominal A.C. r/ms line-voltage to Earth - 230V.
Ia - is the current causing-operation of the protective-devicewithin the specified-time . such as 0.4 or 5 seconds . obtained fromthe manufactures - time / current-characteristics for the particular device-type and rating .

Supposed the manufactures - time / current-characteristic for a 400A - fuse , to BS-88-2.1. gives a value of ( Ia of 2840A ) for a disconnection-time of 5 - seconds . Using the above - formula , the maximum-value of ( Zs ) for the fuse , fordisconnection-time of 5 - seconds and anominal-voltage
( Uo ) of 230V , 230V ÷ 2840A = 0.08Ω

Measured- values of ( Zs ) taking account of conductor -temperature

It should not be forgotten that when comparing ameasured-valued of ( Zs ) with the maximum-value of ( Zs ) allowable for the device used for , fault-protection , account must betaken of the temperature and résistanceof the circuit-conductors . Appendix - 14 of BS-7671: refer .

Provethat the following table-provides instantaneous-disconnection for a BS-EN-60898 & BS-EN-61009-1 - Type B .32A Circuit--breaker using table 41.3. App - 3 .

Zs ≤ Uo /Ia . Table- 41B2

16[SUP]th[/SUP] Edition :
Type- B . 48/In
Type- C . 24/In
Type- D . 12/In

Zs ≤ 240/ 160 = 1.5

48/ 32 = 1.5Ω
240/ 48 = 5. In
32A x 5 = 160A

Mostmanufactures data-shows 3 - 5 x . In for instantaneous-disconnection .

Zs ≤ Uo /Ia .

17[SUP]th[/SUP]Edition : 2008: 2011 :
Type- B . 46/In
Type- C . 23/In
Type- D . 11.5/In

Zs ≤ Uo /Ia . Table - 41.3.

Zs ≤ 230/ 160 = 1.4375 . Round-up to 1.44Ω
46 / 32 = 1.44Ω
230 / 46 = 5. In

Type- B : > 3/In . ≤ 5.0 / In
Type- C : > 5/In . ≤ 10.0 / In
Type- D : > 10/In . ≤ 20.0 / In


If Armoured-Cable is harshly-treated the Amour-wires canbecome-displaced , twisted or stretched , leading to bulges in the sheath-material
Cablesare uniform and circular in cross-section when manufactured , but mishandlingcan result in bulges an kinks which cancause difficulties in pulling into ducts, termination at glands , as well as being unsightly , such problems can be causedby incorrect-pulling from the drum . the introduction of loop and kinks ,pulling round too tight a bend .

 

[amberleaf]

Q) a 6A BS-EN-60898 circuit-breaker is used to protect a circuitwith a , maximum-earth-fault-loop-impedance ( Zs ) of 3.83Ω would be type ? Table - 41.3 . p56
B. ……… above 3/In up to including 5/In
C . ……… above 5/In up toincluding 10/In
D. ……… above 10/In up to including 20/In

Youcan’t predicted what level yourcircuit-breaker will trip on , will trip instantly between three and five timesits rated-current [ 3In x 6A = 18A : 5In x 6 = 30A ]
Type- B current for time , 0.1sec to 5 seconds . Fig - 3A4 , p.301 . BS-EN-60898 & BS-EN-61009-1

Calculating- Earth-fault-loop-impedance . Zs = Uo /Ia .
5 times magnetic-settings - 5 x 6A = 30A : Zs ≤ 230V ÷ 30A = 7.67Ω . re-cap Table 41.3 6A = 7.67Ω .

 

[amberleaf]

Thisone always trips up . Q/As -&-s . 2392 . 2394

Q). When testing a 100mA RCD themaximum-test-current applied via the test-instrument will be ? ( G )
3 x In
5 x In
I x In

 

[amberleaf]

RCDscannot detect . Short-circuits or Overloads . due to their design .

Tosummarise the RCD tests . 30mA -Testing .

IΔn / 2. No-tripin 2 seconds . 30mA ÷ 2 = 15.

 

[amberleaf]

Because it’s Not in the 17[SUP]th[/SUP]- Edition : 2008: or 2011: Doesn’t not mean it did not Exist . “ Pastto Present “ :icon_bs:

Earthing& Bonding - 2[SUP]nd[/SUP] Edition
Incorporatingthe requirements of BS-7671:2001:
IncludingAmendment , No - 2 .

Looped-main-equipotential-bonding . 2006.

Main-equipotential-bonding-conductor(s) should , ideally, Not be looped from service to service . ( METto Water - Gas )

Solution:
Wherea common-bonding-conductor-loops In and Out,to connect to an ,extraneous-conductive-part . The protective-conductor should beleft-unbroken at the connection .

Thisis so that the ( Continuity ) to other-items connected to thebonding-conductor will not be detached , for example . as a result of work beingcarried out to pipework , refer , Regulation - 528-02-04.

Wherea wiring-system is to be installed in proximity to a non-electrical-service, it shall be so arranged that anyforeseeable-operation carried out on either-service will not cause-damage tothe other .

528.3.3. : 17[SUP]th[/SUP] - Edition .
Wherean electrical-service is to be installed in proximity to a non-electrical-services , it shall be so arranged that anyforeseeable-operation carried out on either-service will not cause-damage tothe electrical-service or the converse . Etc .

Apermanent-label bearing the Words “ Safety Electrical Connection - Do Not Remove “ isrequired in a visible-position at or near the point of connection ofevery-main-bonding-conductor to an , Extraneous-conductive-part , and at themain-earthing-terminal where this isseparate from the main-switchgear - Regulation - 514-13-01.

514-13: 2002 / 2004 : Warning-notices: earthing and bonding-connections .
514-13-01 . A permanent-label to BS-951 , with the words “ SafetyElectrical Connection - Do Not Remove “ shall be permanently-fixed in avisible-position at or near : Etc .

514-13: Warning-notices :earthing and bonding-connections .
514-13.1: A durable-label to BS-951 , with the words “ SafetyElectrical Connection - Do Not Remove “ shallbe permanently-fixed in a visible-position at or near : Etc .

Regulation- 528-02-04 :
Wherea wiring-system is to be installed in proximity to a , non-electrical-serviceit shall be so arranged that any , foreseeable-operation carried out on eitherservice will not cause-damage to the other.