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RCD's

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  • 01-07-2012 7:03pm
    #1
    Mr Magnolia
    Moderators, Recreation & Hobbies Moderators Posts: 10,435 Mod ✭✭✭✭


    Anyone ever replace an old fuse board to find that the 30mA RCD trips on the new installation? I know it's most likely down to mixed neutrals but I was wondering what the correct/appropriate approach would be?


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    #2
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Mr Magnolia wrote: »
    Anyone ever replace an old fuse board to find that the 30mA RCD trips on the new installation? I know it's most likely down to mixed neutrals but I was wondering what the correct/appropriate approach would be?

    Had it happen a few times. I even once had one that was tripping with the main switch in the DB off.

    What condition was the wiring of the house in?

    Switch immersion off at the immersion switch. Try RCD then.

    Plug everything in the house out. See if that sorts it. If it does, plug items back in one at a time. If one trips it, it can be the item, or it can be the neutrals into earth and earths into neutral in that socket, which wont trip RCD until an item is plugged into that particular socket. If the RCD trips with an item into any socket, try a different item, a radio is good. If it trips in any socket on a circuit, then that circuit probably has a neutral connected to earth or neutral earth fault.

    If not, switch off every MCB in the new board, not just sockets, but everything. See if that allows RCD to be switched on.

    If it does, switch on 1 MCB at a time and see do any trip the RCD. If one does, make sure its neutral is in the appropriate neutral bar.

    There are tests that can be done at the board to find a socket circuit that has a neutral earth fault, but try the above items first.


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    #3
    meercat
    Registered Users Posts: 4,745 ✭✭✭meercat


    robbie7730 wrote: »
    Had it happen a few times. I even once had one that was tripping with the main switch in the DB off.

    What condition was the wiring of the house in?

    Switch immersion off at the immersion switch. Try RCD then.

    Plug everything in the house out. See if that sorts it. If it does, plug items back in one at a time. If one trips it, it can be the item, or it can be the neutrals into earth and earths into neutral in that socket, which wont trip RCD until an item is plugged into that particular socket. If the RCD trips with an item into any socket, try a different item, a radio is good. If it trips in any socket on a circuit, then that circuit probably has a neutral connected to earth or neutral earth fault.

    If not, switch off every MCB in the new board, not just sockets, but everything. See if that allows RCD to be switched on.

    If it does, switch on 1 MCB at a time and see do any trip the RCD. If one does, make sure its neutral is in the appropriate neutral bar.

    There are tests that can be done at the board to find a socket circuit that has a neutral earth fault, but try the above items first.


    agree robbie
    try the immersion first
    i find the best approach is to disconnect all neutrals
    do a quick continuity test to earth individually
    if nothing shows up then possibly there is a neutral on the wrong buss-bar or a neutral/live taken from socket circuit to use on a light circuit

    dont forget all other tests and test records should be completed too


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    #4
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    meercat wrote: »
    agree robbie
    try the immersion first
    i find the best approach is to disconnect all neutrals
    do a quick continuity test to earth individually
    Indeed, I remember the post I put up about that myself a while back which you linked to the last time this problem came up:)

    That`s what I do after plugging everything out and switching all MCB`s off to see can the problem be isolated.

    Its usually a neutral earth mix up in a socket, or neutral on wrong bar in the board. Earths into neutral terminal and neutrals into earth terminal at a socket, but not mixed with each other, wont show up except when an item is plugged into that particular socket. I had one like that before which stopped tripping when the fridge was plugged out, but it was nothing wrong with the fridge, but neutrals and earths into wrong terminals.


    The problem itself can be tricky to find, but which circuit it is on shouldnt be to hard to identify. Junction boxes is another possibility.


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    #5
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    Mr Magnolia wrote: »
    Anyone ever replace an old fuse board to find that the 30mA RCD trips on the new installation? I know it's most likely down to mixed neutrals but I was wondering what the correct/appropriate approach would be?

    I will give you a buzz :)


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