Re-take - Useful Information for 2394 :

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Facts.

Past& Present . 2001/ 2011:
Thisis meant as a reference . “ learning-Curve “

Useful-junk.
RCBOs to BS-EN-61009-1 ( 41B2 & 41C)
41.3 - Now . 17[SUP]TH[/SUP]Edition for RCBOs . see - 411.4.9.

Thisis Why . Maximum ( Zs ) DATA is included for RCBOs in chapter - 41 . You areaffectively being asked to ( MAKE ) the RCBO work using its. ( MCB ) function on TN-system . Chapter - 41 .protection against Electric-shock .

Maximum-earth-fault-loop-impedance. limits or protected-conductor-résistance(s) as those for ( Circuit-breaker ) this can raise question as RCBO-acting as . residual-current-devices .will trip on fault to earth at much-greater loop-impedance(s) thancircuit-breaker(s) . This reason for listing these devices in this table isthat in . TN-system it is preferable for installation(s) . to be designed forRCBOs to operate in an ( Overcurrent-mode ) when providing ( Indirect-shock-protection) when RCBOs are operating in ( Overcurrent-mode ) they are ( Voltage-independent ) whenthey are operating as ( RCDs ) they aredependent upon a driving-voltage being supplied to the Electronics

This.Agreement within the . International-Electrotecnical-Commission . that voltage-dependent-RCDs shouldoperate at driving-voltages as low as ( 50V ) so that the effects
Ofcollapsing voltages - under-fault-conditions are nullified . however . in theevent of .Open-circuit-neutral-it is possible the a RCBO . will not operate inRCD-mode for fault-to-earth . consequently a design for a TN-system should ensure that RCBOs operate in ( Overcurrent-mode ) for indirect-shock-protection . & leave theRCD to provide . Supplementary-protection against direct-contact .

For. TT- installation(s) or a TN-installation . where the designer is obliged by particular-circumstances toaccept . high-earth-fault-loop-impedance - BS-7671: allows use of “ RCBOs“ & of course “ RCDs “ at muchhigher-loop-impedance .

411.4.9. : Where an RCD . is used to satisfy therequirements - 411.3.2.2. the maximum values of earth-fault-loop-impedance intable - 41.5. may be applied for . non-delayed RCDs to BS-EN-61008-1 & BS-EN-61009-1 . & BS-EN-61009-1 fornominal-voltages . Uo of 230V . in such cases an Overcurrent-protective-deviceshall provide protection against Overload-current & fault-current inaccordance with Chapter - 43 .

Table41C : - 2004
Regulation- 413-02-20 : 413-02-16 :
413-02-16 : ifprotection is provided by a residual-current-device . the following conditionshall be fulfilled ( Zs - IΔn ≤ 50V )
Where :
Zs) is the earth-fault-loop-impedance in Ohms .
IΔn) is the rated residual-operating-current of the . protective-device in amperes.

413-02-16 - ( 16[SUP]TH[/SUP]) has not been included in the 17[SUP]th[/SUP] Edition .
Youare left with 411.4.9.which refers you to Table 41.5.

531.3.1. - RCDs in a TN- system .
Ina TN-system . where for certain equipment in a certain part of the installation. the requirement of Regulation - 411.4.5. cannot be satisfied . that part may beprotected by an RCD . Note :- that if an Earth-Electrode is used then -411.5.1. to 411.5.3. applies

413-02-20 : The following condition shall be fulfilledfor each circuit : ( R[SUP]a[/SUP] Ia ≤ 50V )
Where :
R[SUP] a[/SUP] ) is the sum of the resistances of the earth-electrode & theprotective-conductor(s) connecting it to the . Exposed-conductive-part .
Ia) is the current causing the . automatic operation of the protective-devicewithin 5s .
When: the protective-device is a residual-current-device . ( Ia ) is the ratedresidual-operating-current ( IΔn ) .

411.5.: 411.5.3.: Where an RCD is used for fault-protection. the flowing conditions shall be fulfilled :
i). The disconnection-time shall be that required by Regulation - 411.3.2.2. or 411.3.2.4. &
ii). R[SUP] a[/SUP] x IΔn ≤ 50V .

2001 / 2004 : did not define an . RCBO .
p.34 :Residual-current-operated-circuit-breaker - ( With ) integral-Overcurrent-Protection- RCBO .
-A residual-current-operated-switching-device .
-Designed to perform the functions of ( Protection ) against . Overload & / orShort-circuit .

(By Definition -Residual-Current-Circuit-Breaker - with Overcurrent-Protection )Combined-functions of . MCB & RCD .in one-unit
RCBO. refers to a ( Device ) that disconnects a circuit . whenever it detects thatthe “ Current “ is not balanced between the Energized-conductor & thereturn-Neutral-conductor .
PlainEnglish : This device has Two-Circuit(s) for detecting an ( Imbalance ) &an ( Overload ) Interrupt-method ?? . Trip or Breaker . RCD / MCB . - RCBO

Magnet-sensorin an MCB - RCBO is a fast acting-device to respond to current-flow .that are much higher than norm .
RCBO. this is simply an MCB . with an Additional-Sensor to ( Detect ) residual-current(s)

411.4.5.: is for TN- not TT- system
Themost common TN-C-S & TN-S . ( Ze - 0.35Ω & 0.8Ω ) Maximum Impedance .

RCDs. aren’t intended to operate on . Line-to Line . or Line-to Neutral faults . asthere would not be an residual-current to detect .

 

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What’s in a Word . ??

Definitions : Things come things go .!! 16[SUP]th[/SUP]Edition to 17[SUP]th[/SUP] Edition.

The current flowing in the (Protective-conductor ) is often referred to as ( Earth-leakage-current ) thedefinition of ( Protective-conductor-current ) from Part-2 of the 16[SUP]th[/SUP]Edition of BS-7671 :

Protective-conductor-current :Electric-current . which flows in a ( Protective-conductor ) under normaloperating conditions .
The term . ( Earth-leakage-current ) is no longer defined .

in the 17[SUP]th[/SUP]Edition of BS-7671:2011 : (Protective-conductor-current ) is defended as :
Protective-conductor-current . -Electric-current appearing in a Protective-conductor such as ( leakage-current )or electric-current resulting from an . Insulation-fault .

 

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Why use the Word “ Final-circuit“ History in the Making . Yeah

9[SUP]th[/SUP] Edition : Entitled . “Wiring-Rules “ Issued in 1907 .
4.1) . Sub-Circuit . A sub-circuit is a branch circuit connected to a distribution-board . fed from a ( Main-circuit )& may either feed a further distribution-board or be a ( Final-sub-circuit) which does not feed a distribution-board arid to which lamps & or other (Current-consuming-devices are connected )

14[SUP]th[/SUP] Edition : ( Final-sub-circuit )
An outgoing circuit connected to adistribution-board & intended to supply electrical energy tocurrent-using-apparatus . directly or through . Socket-outlets orFused-spur-boxes .

15[SUP]th[/SUP] Edition : (Final-circuit )
Final-circuit . A circuit connecteddirectly to current-using-equipment . or to a Socket-outlet or Socket-outlet(s)or other point for the connection of such equipment .
16[SUP]th[/SUP] Edition :
Final-circuit . A circuit connecteddirectly to current-using-equipment . or to a Socket-outlet or Socket-outlet(s)or other point for the connection of such equipment .
17[SUP]th[/SUP] Edition :
Final-circuit . A circuit connecteddirectly to current-using-equipment . or to a Socket-outlet or Socket-outlet(s)or other point for the connection of such equipment .
17[SUP]th[/SUP] Edition2011 :
Final-circuit . A circuit connecteddirectly to current-using-equipment . or to a Socket-outlet or Socket-outlet(s)or other point for the connection of such equipment .

 

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Typesof . Fault-condition . “ Basic “

Thereare Two-basic types of . Fault-condition .

-A Short-circuit . This is any fault . between Live-conductor(s) - that is Three-line-to-Line . orLine-to-Neutral .
-An Earth-fault . This is a fault . Live-conductor & either an .Exposed-conductive-part . or the Protective-conductor of the circuit . ( PE - protective-earth . CPC )

 

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Useful-Junk. With TT-systems . expect anything from -&-s . Exams ??? 2394 : this will help . Yeah

TT- system . ( Rod - R[SUP]A [/SUP] )
Inorder to obtain a value of ( Ze ) for an installation-forming-part of a TT-system . it is crucial that ( R[SUP]A[/SUP][SUP] [/SUP]) is added to the . maximum-value of.External-earth-fault-loop-impedance . Obtained from the DNO . We know its . 21Ω . O.S.G. p.11.

Weknow it’s the case of . Value - 21Ω - formaximum-external-earth-fault-loop-impedance . for an installation forming part of TT-system . & that the resistancee of the installationearth-electrode ( R[SUP]A [/SUP]) Example - is 75Ω . the valueof ( Ze ) is therefore equal to . 96Ω . ( 75Ω + 21Ω = 96Ω )


Regulation. p.39 - ( R[SUP]A [/SUP]) the sum of the resistancee of the . earth-electrode & the protective-conductorconnecting it to the . Exposed-conductive-parts . ( Ω )

 

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2394: your only worried about . Measuring .. stick to that at the Mo .

Prospective-fault-current. must be determined .

Regulation- 313.1. requires the ( PFC ) prospective-short-circuit-current . at the Origin of an installation to be determined
Amongst-othercharacteristics of the supply .

Thedetermination may be carried out by .
- Calculation.
- Measurement.
- Enquiry.

Inaddition . Regulation - 434.1. requires the prospective-short-circuit &prospective-earth-fault-current(s) to bedetermined at every-point of the installation
- Calculation.
- Measurement.
- Enquiry.

Maybe used as the means of determination .

Whatis meant by the “ Words “ Every-relevant-point - 434.1. that is the regulation requires the ( PFC ) at . Every-relevant-point of theinstallation - to be determined
Simply. Every-relevant-point . means
Every-point where . for reasons of confirmingcompliance with on or more of the requirements of . BS-7671:2011: it isnecessary to ( Determine ) the . PFC

 

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2394: Basics to start on . Provision for .

Fault-protection . where ( ADS ) is applied is . protective-earthing . protective-equipotential-bonding . & automatic-disconnection in case of a Fault .
The. fundamental-principle . of this protective-provision is that the .characteristics of the device(s) providing-protection . must coordinated withthe . Protective-earthing & equipotential-bonding - arrangements for the installation & the .Earth-fault-loop-impedance of thecircuit-so-protected .

 

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Part- 4 . Protection for Safety

Chapter- 41 . Protectionagainst Electric-shock.
Section- 411 . Protection-Measure . Automatic-Disconnectionof Supply . - ( ADS ) by operation ofProtective-device .
411.3.- Requirements for fault-protection .
411.3.1.- Protective-earthing & protective-equipotential-bonding .
411.3.1.1.- Protective-earthing . Exposed-conductive-parts . shall be connected by aprotective-conductor . Etc .

 

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Section- 411 . Protection-Measure . Automatic-Disconnectionof Supply .

411.3.3.- Additional-protection.
InA.C. - systems . Additional-protection by means of an RCD . having ( IΔn ) not exceeding . 30mA ) shall beprovided for .
- Socket-outletsnot exceeding . 20A rating for use by .Ordinary-persons .
- Mobile-equipmentnot exceeding 32A . rating for use Outdoors .

p..31. By definition. Mobile-equipment
(Portable-equipment - ( deprecated)) Electrical-equipment which is movedwhile in ( Operation ) or which can easily bemoved from . one place to another while ( Connected tothe Supply )

 

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Prospective-short-circuit-current.

Anassessment of the ( PSCC ) at the origin of the installation isrequired by . regulation - 313.1. in order to establishthat device(s) such as Overcurrent-protective-device(s) . at the Origin & elsewhere have. short-circuit-capacities . - ( Breaking-capacity ) forfuses & . making / breaking capacities for . protective-devices other than . fuses .for Circuit-breakers . ofnot less-than the . prospective-short-circuit-currents .

Regulationrefers only . the Short-currents at the Origin

Short-circuit-characteristics . of public-electricity. DNO . & co-ordination of .Overcurrent-protective-devices . on 230V - single-phase supplies up to 100A .

 

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2394: something for studying .

410.3.2. View to ensuring compliance .
Recognizedprotective-measures . BS-7671:2011:

• Protectionagainst Electric-shock .

ThisChapter - 41 . deals with ( Protection )against electric-shock as applied to electrical-installation(s)

Protective-Measures: 2011:

A protective-measure must consist of provision of Basic-protection. & provision of Fault-protection . Which are Independent .

Independent ) Basic-protection : isprovided by Insulation & Barriers & Enclosures . Consumer-Unit . it’s a start .

Independent ) Fault-protection : isprovided by .
-Protective-earthing ………. ( in case ofFault )
-Protective-equipotential-bonding . ………. ( in case of Fault )
- ( ADS ) Automatic-disconnection of supply . ………. ( in case of Fault )

Basic-protection: is defined as . Protection against electric-shock under . fault-free-conditions . p.51 .
Basic-protection is provided to protect-Person orLivestock . coming into direct-contactwith ( Live-parts )
( Live-parts ) is defined as . p.30 .
Aconductor or conductive-parts intended to be energized in normal-use .including a neutral-conductor but . by convention not a . PEN-conductor .

p.28. Protection under-fault-conditions or ( Fault-protection ) is defined as. Protection against electric-shockunder . single-fault-conditions .

Note : Low-voltage-installation(s) System & Equipment. fault-protection ( generally-corresponds ) to protection againstindirect-contact . mainly with regards to failure of basic-insulation .Indirect-contact is “ Contact of persons or livestock with ( Exposed-conductive-parts ) whichhave become . Live under-fault-conditions “

( Exposed-conductive-parts ) is defended as .
p.27. ( Conductive-part ) of equipment which can be touched & which is not-normally live . but whichcan become . live-under-fault-conditions

( Conductive-parts) which are Accessible . Copper-pipes . Equipment . must not be Hazardous-live . Etc

personcould receive an electric-shock ( Single-fault-conditions ) is in contact with the . Metal-enclosure of an item of . Class-1 equipment which has become .live-under-fault-conditions . thepotential of the Metal-enclosure is higher than that of the .main-earthing-terminal of the installation . & that of a potential-difference created by the passage of ( fault-current ) through the impedance of the .circuit-protective-conductor(s) &the means of Earthing .

Protective-earthing 411.3.1.1.
Requiresall . Exposed-conductive-parts . to be connected to a protective-conductor which in turn isconnected to the ( MET ) if there is anyFault-conditions . Via the Earthing-conductor to the . Means of Earthing .

411.4.4. The following types of Protection-devices maybe used for Fault-protection .
i) . Overcurrent-protective-device .
ii). RCD .
Note 1 : Where an RCDis used for . Fault-protection . the circuit should also incorporate an .Overcurrrent-protective-device .

AProtective-device . maybe . Fuse . Circuit-breaker . RCD . RCBO .

Protective-equipotential-bonding. 411.3.1.2.
Ineach-installation . main-protective-bonding-conductors complying with . Chapter- 54 . are required to connect to the ( MET ) main-earthing-terminal .
Extraneous-conductive-parts such as.
-Water-pipes .
-Gas-installation-pipes .
-Other-installation-pipework . & Ducting
-Central-heating & Air-conditioning -systems .
-Exposed-metallic-structural-parts of thebuilding .

Familiarforms in which RCDs are used to provide . Additional-protection
Wherean RCD is used to provide . Additional-protection . to comply with the requirements ofregulations - 415.1.1. the RCD must have .
i) rated residual-operating-current ( IΔn ) not exceeding 30mA .
ii)Operating-time not exceeding . 40mS at a rated residual-operating-current ( x5 ) as required by theapplicable-standards .

Recognizedprotective-measures . BS-7671:2011:

Protective-measures.

(ADS ) automatic-disconnection .
- Basic-protection provided by - Insulation or Barriers & Enclosures .
Insulation- Basic-insulation of Live-parts . Live-Conductors are usually allocated with this protective-provision .
2394 Consumer-unit : Barriers & Enclosures . Barrier protection form contact with busbar . Your - Enclosure . will be Class - 11 . Ordinary-persons
- Fault-protection provided by - Protective-equipotential-bonding . ( ADS ) Automatic-disconnection .

 

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Pontto Note . “ Private-Landlord “
2394: when to a Job today . Client asked me to change a , Pendent-set . forMetal-light-fitting . after a quick inspection . This was my Reply .

• Warning : You Do not have the provision forEarthing-Metal-Equipment . ( Risk ofElectric-shock )
Donot replace installed-lighting-fittings or switches with . metal-lighting-fitting or switches . ( Sticky-label in my toolbox onto the Consumer-unit )

Hada word with the Client . can fit Class-11 lighting . her reply was what is that . !!! cut to the chase - No-Earthing . Ask the Landlord .

 

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Paul-m . you’re the first person to thank me . Thank-You .
As iv.e had no more thank you.s .

Forth-timearound the circuit . My stuff must be Boring .

 

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Circuit-detail-labels.
Havebeen designed for electricians to leave on . Distribution-boards . when workhas been completed . so that any person wishing to operate . maintain or alteran installation can do so with (Reasonable-safety )

Circuit-details: as we are reminded of . 514.9.1.
-Circuit-number .
-Circuit-designation - for distribution-circuits .
-Type of wiring .
-Reference-methods . see Appendix - 4 . BS-7671:2011:
-Number of points-served .
-Circuit-conductors - CSA - mm[SUP]2[/SUP] . Line . Neutral . CPC . conductors .
-Maximum-disconnection-time . permitted by BS-7671:2011:
-Overcurrent-protective-devices . Type - ( BS-EN - numbers ) . Rating - ( A ) Capacity - ( kA ) RCDs - Operating-current - ( IΔn ) Maximum - ( Ze - Ω ) permitted by
BS-7671:2011:


- - - Updated - - -

2394: I cant stress enough the importance of GN-3 . By its very name . “ Guidance “ What’s in a Book . Answers

GN-3- 2.3. - 514.9.1.

Diagrams. Charts or Tables .

The. Health & Safety at Work Act - 1974. generally requires relevant-information to be available as an . Aid to safe-use. Inspection . Testing. maintenance . This may include those items listed in . Regulation - 514.9.1.

9). The type & composition of circuits . including-points of utilisation .number & size of conductors & type of cable . This should include theinstallation-method shown in . Appendix - 4 . section - 7 . “ Methods of installation “ of BS-7671:2011:

10). The method used for compliance with the requirements for . basic &fault-protection & . where appropriate . the conditions required for ( ADS) - 410.3.2.
11). The information necessary for the identificationof each-device performing the . functions of protection . isolation &switching . & its location .
12). Any circuit or equipment . vulnerable to a particular-test.

Regulations . A -legible-diagram . Chart or Table orequivalent form of information shall be provided indicating in .

514.9.1. just a reminder .

i) - Type & composition of ( Each-circuit points of utilisation served ) number &size of conductors . type of wiring .
ii) - Method used for . compliance with regulation . 410.3.2.
iii) - Information-necessary for the ( Identification of each-device ) the functions of ( Protection )
iv) - Any circuit or equipment ( Vulnerable to a typical-test )

Regulationsreminds us . for simple-installation(s) the . foregoing information may be given in a ( Schedule)
Adurable-copy of the ( Schedule ) relating to a . distribution-board shall be provided within or adjacentto ( Each distribution-board ) Etc .

Circuit-detail-labels. if we look on the Internet . theselabels will fall in to the category of. 514.9.1.

514.9.1. - ( Identification of a Protective-device )
Protective-device shall be arranged & indentified so thatthe circuit-protected may be easily indentified . Diagrams & Documentation .

Legible-diagram. Chart or Table or equivalent form ofinformation shall be provided indicating in
i) - Type & composition of ( Each-circuit points of utilisation served ) number &size of conductors . type of wiring .

inAddition ( Each-circuit -breaker ) needs to be marked-up to show its function .- refer 514.8.1.
514.8.1: A . protective-device shall bearranged & indentified so that the . Circuit-protected may beeasily-recognized


Somethingto think about .

Myunderstanding is that your . Schedule ofTest-results . will suffice as a ( Circuit-Schedule ) Your leaving a copy of the Certificate there .
Put !! ) The fact of the matter . Schedule ofTest-results . it on the Certificate already is beside the point. This Certificate may not be Availableto the next-person for information available .

( He who never made mistakes never made “ Anything “ )

Circuit-detail-labels. it’s a start .

Havebeen designed for electricians to leave on . Distribution-boards . when workhas been completed . so that any person wishing to operate . maintain or alteran installation can do so with (Reasonable-safety )

Circuit-details: as we are reminded of . 514.9.1.
-Circuit-number .
-Circuit-designation - for distribution-circuits .
-Type of wiring .
-Reference-methods . see Appendix - 4 .BS-7671:2011:
-Number of points-served .
-Circuit-conductors - CSA - mm[SUP]2[/SUP] . Line . Neutral . CPC . conductors .
-Maximum-disconnection-time . permitted by BS-7671:2011:
-Overcurrent-protective-devices . Type - ( BS-EN - numbers ) . Rating - ( A ) Capacity - ( kA ) RCDs - Operating-current - ( IΔn ) Maximum - ( Ze - Ω ) permitted by
BS-7671:2011:

 

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( Circuit-loop-impedance )
Earth-fault-loop-impedance. ( Zs ) is an essential-factor . where the most commonly used .Protective-measure - ( ADS )

Fault-conditions Line to Earth-fault . T&E . 2.5mm[SUP]2 [/SUP] . in this case . Circuit-loop-impedance . Line -R[SUP]1[/SUP] & Circuit-protective-conductor R[SUP]2[/SUP] . CPC

p.39. Formula for . Earth-fault-loop-impedance . Zs = Ze + ( R[SUP]1[/SUP]+ R [SUP]2[/SUP] ) ohms

( R[SUP]1[/SUP]+ R [SUP]2[/SUP] ) 2394 : Testing - Ω . Schedule of Test-results .
R [SUP]2[/SUP]) regulation reminds us . ( CPC ) of a distribution . orFinal-circuit . 2394 : but in our case .at the Consumer-unit .