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  1. GBDamo
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    GBDamo Regular EF Member

    Location:
    UK
    I have been asked to look into a random tripping RCD.

    The installation is quite simple, now only only four circuits,

    None RCD protected side has only the lights and a redundant 16A MCB 2.5mm radial for which no accessory could be found, possibly disconnected outside lights but the circuit was still live, this has been disconnected and put in connectors in the CU.

    RCD side has a 16A MCB 2.5 radial with only one double socket outlet, a 32A MCB ring doing the majority of the sockets (possibly with a ring off the ring but that's another story), a 20A 2.5mm radial doing living room sockets and finally a 40A MCB 6mm redundant circuit serving a removed shower.

    All IRs pass although the 20A radial and 32A ring both had low readings at 2-3MOhms. All other tests pass comfortably.

    However the 40A ex-shower circuit still had the Neutral and CPC terminated in the CU, the other end could not be located, probably cut off and plastered in the bathroom wall.

    I have disconnected the the Neutral and CPC for the ex-shower and made them safe in terminal blocks in the CU.

    After 4 days there have been no more random tripping whilst I've tidied up some loose ends I'm concerned that I haven't really found the fault.

    Could a Neutral and CPC buried in a damp wall like this cause an RCD to trip?

    Any thoughts welcomed.
     
  2. Andy-1960
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    Andy-1960 Electrician's Arms

    Location:
    Wolverhampton
    Yes
     
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  3. SparkyChick
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    SparkyChick Making a banana smoothy for my fave gorilla Electrician's Arms

    Location:
    South Wales
    Business Name:
    SparkyChick
    What he said :) ^^^^
     
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  4. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Yep, a good chance the old shower circuit could cause this. Perhaps continuity / ir test that cable and see?
     
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  5. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    But he said he's disconnected the shower ...

    I would recommend the customer keep a record of when it trips.
     
  6. SparkyChick
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    SparkyChick Making a banana smoothy for my fave gorilla Electrician's Arms

    Location:
    South Wales
    Business Name:
    SparkyChick
    I read it as the shower was connected when it was tripping and in the process of investigating the tripping, he disconnected the old shower cable.
     
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  7. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    I think you are correct ...
     
  8. GBDamo
    Offline

    GBDamo Regular EF Member

    Location:
    UK
    To clarify the electric shower was replaced by a bar mixer before my friend bought the house but the circuit for the shower is still in place. That is it runs from the CU to a location unknown, assumed to be cut off and plastered into the bathroom wall.

    The live had been disconnected in the CU but the Neutral and CPC had not.

    This tripping has been on and off for the three years they have had the house.
     
  9. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    Good response.

    Yes leaving the neutral and earth in a wall is never a good idea.

    I would leave the cpc connected to the cu
     
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  10. GBDamo
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    GBDamo Regular EF Member

    Location:
    UK
    Been done Mordoch, it's totally random no correlation with anything or any appliance. Has even gone overnight with nothing on, literally nothing.
     
  11. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    ^^ sometimes these things happen.

    I had been investigating random tripping in a very big 3 story house a couple of years ago. Dual RCD board

    In the end I recommended the customer changed to a rcbo board ....
    Which was implemented.

    A few months later the 3rd story socket circuit started to trip.... Eventually I found a cable disappearing down a wall behind the shower room below. I disconnected the spur and it's never tripped again.

    Very trying to deal with.
     
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  12. Risteard
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    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    You could connect all cores of the former shower cable to the Earth bar in the DB.
     
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  13. GBDamo
    Offline

    GBDamo Regular EF Member

    Location:
    UK
    Its nice to find a screw through a cable or some such that you can point to and say "that's it" but it's not always the case.

    Just don't want to be getting a free breakfast under false pretenses.
     
  14. GBDamo
    Offline

    GBDamo Regular EF Member

    Location:
    UK
    Just to ensure it it doesn't become and remain live due to coming into contact with another live conductor?

    bed time now, thanks for the assistance all.
     
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  15. Risteard
    Offline

    Risteard Electrician's Arms

    Location:
    Derry, Ireland
    Business Name:
    Walsh Electrical Services
    Well, perhaps, although the more likely scenario is someone reconnecting it in the DB. Hopefully if all cores are earthed they may stop and think. (No guarantee there though, I'm afraid. Stupid never fails to surprise...)
     
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