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  1. ac/dc
    Offline

    ac/dc EF Member

    EVENING ALL

    HAVING BEEN AROUND THIS OLD BLOCK OF FLATS FOR SOME INSPECTION
    I CAME ACROSS A LIGHTING CIRCUIT ON THE HALLWAY (5 FLOORS ) WITH NO CPC , BUT NO SWITCHES.
    WIRED WITH 2.5mm SINGLE CORE ON METAL CONDUIT AND RCBO PROTECTED
    STAIRCASE LIGHTING CIRCUIT ALSO WITH NO CPC AND ON BORROWED NEUTRAL WIRED WITH 2.5 mm ON 10 A MCB
    (TRYING TO CHANGE FROM MCB TO RCBO)
    I COULDN'T FIND WHERE IS BOROWED FROM (NOT FROM HALLWAY LIGHTING CIRCUIT).
    THE 13 WAY RCD - COMMUNAL DB IS ON THE BASEMENT AND WIRES IN THE METAL TRUNKING ARE A SPIDER WEB GOING IN AND OUT
    OF THE TIMERS ALL SINGLE CORE.

    PLEASE, ANY FAST WAY OF FINDING THE BORROWED NEUTRAL OR DO I HAVE TO DISCONN. ALL THE WIRES AT THE D.B.


    THX . IN ADV.
     
  2. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    if the circuit is singles in metal conduit, then the conduit is probably the cpc. if you need to find the borrowed N, then it's a case of disconnecting and testing till you find it. no quick fix here, mate.
     
  3. ackbarthestar
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    ackbarthestar Trusted Advisor

    Location:
    A Zoo near YOU
    I assume that the shared neutral is across the hallway and staircase lights?
    It would only be 'borrowed' if the parts of the lighting circuit are connected across two different breakers. Placed in one breaker or RCBO and the lights should be ok. that is as long as the In rating is able to cope with the load.
     
  4. ac/dc
    Offline

    ac/dc EF Member

    HI
    WENT THIS MORNING TO THIS PROPERTY AGAIN AND THERE IS NO CPC (EARTH) ON THE LIGHTING CIRCUIT.
    2.5 mm SINGLE CORE LINE & N. WIRED IN METAL CONDUIT BUT THERE IS NO CONTINUITY.
    RCBO -16A
    PLEASE, WHAT WOULD YOU WRITE ON THE CERT. IN TERMS OF ZS , RCBO DISCNN. TIME, ETC.



    THX .IN ADV.
     
  5. ackbarthestar
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    ackbarthestar Trusted Advisor

    Location:
    A Zoo near YOU
    The cpc continuity is likely to have existed once upon a time, but after a period of time where there have been additions, alterations, loosened joints and possible corrosion the continuity is no longer available.
    As it is a communal, public area and the switches and lights have exposed conductive parts then it is a failed circuit and should be coded appropriately.
    You cannot rely on the RCBO to provide protection where there isn't a suitable earth fault path. (531.2.5) So IMO it would be C1
     
  6. SYKRAPS
    Offline

    SYKRAPS Regular EF Member

    Location:
    Yorkshire
    Why are you changing from MCB to RCBO if the board's main isolation is an RCD?
     
  7. paulgrahamsmith
    Offline

    paulgrahamsmith Farmelectrics Electrician's Arms

    Location:
    Wirral
    Business Name:
    Farm electrics
    put your clamp meter around neutral and nock breakers of one at a time quick way to find what circut the neutral has been borrowed from good luck
     
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