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Discuss Nightmare of a day. RCD tripiing under any load in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. brizospark
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    brizospark Electrician's Arms

    Location:
    Kent
    Have had one of them days. I had a board change to do and a few other bits and bobs so everything was going great until I tried to put power back on.

    Basically I have replaced a 3036 board with a split load Wylex board. One half of the board is working fine but the other half's RCD is tripping as soon as anything is plugged into it.

    If I remove all plugs from sockets then the RCD holds but as soon as I plug anything in, kettle, sky box, TV, it trips instantly. On this side of the board is the cooker, 1 x lighting circuit and 2 x ring mains, funny enough the RCD isn't tripping when the lighting circuit or cooker is on.

    Now I have checked that I have neutrals from correct circuits going to the correct neutral bar, several times and these are OK. I tried replacing the RCD itself with the one that was OK and it still tripped. What else is strange is that the kitchen ring is on the side of the board which is fine but if I plug anything into a kitchen socket the RCD which isnt even protecting this is tripping!! I opened up sockets and everything looked OK but it was getting late on so I replaced the offending RCD with a main switch I had in van just so the couple have power on tonight before I go back again tomorrow. Switched on with RCD removed and everything fine.

    Anyone had experience with this problem before? Any advice much appreciated
     
  2. sima24
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    sima24 Guest

    Sounds like borrowed neutral to me. Have u tried putting the 2 lighting circuits on the same rcd?
     
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  3. sima24
    Online

    sima24 Guest

    Has it been tested to rule anything else out?
     
  4. Brightspark2
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    Brightspark2 Electrician's Arms

    Location:
    North West
    Everything test out ok?...


    Borrowed neutral?....or shared neutral whatever you want to call it.
     
  5. Marvo
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    Marvo GMES....You absolute beauty. YOU ROCK DUDE!!!! Staff Member

    Location:
    South Africa
    With a borrowed neutral, shared neutral or split neutral or whatever you call it the RCD won't trip until there's some current flowing. If there's no load current then there's no fault current so it will hold if you unplug everything and turn all the lights off.

    Rather than using the RCD to do your fault finding use your normal tester and your mega tester if necessary.
     
  6. trev
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    trev Regular EF Member

    It could also be a neutral to earth fault but your IR testing ruled that out. Right?
     
  7. Dizzy_Maskell
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    Dizzy_Maskell Electrician's Arms

    Location:
    Cheshire
    Yes sounds like to me like a borrowed neutral. Have they had extensions done you will need to break each circuit up and test in stages some where some one had tapped into a neutral or you could try try putting all socket circuits on one side of the RCD
     
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  8. brizospark
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    brizospark Electrician's Arms

    Location:
    Kent
    Thanks for replies guys yes everything tested out ok. So we are looking at a borrowed neutral most likely then?
     
  9. sledgehammer
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    sledgehammer Regular EF Member

    Location:
    Swindon
    Neutral to earth fault, megger out.
     
  10. i=p/u
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    i=p/u Trusted Advisor

    Test before touch
     
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  11. sledgehammer
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    sledgehammer Regular EF Member

    Location:
    Swindon
    Sorry should've said, shows its self as you try to draw power. As you said its as soon as you plug in and use power.
     
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  12. wersolaruk
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    wersolaruk Regular EF Member

    Sounds like a existing fault somewhere on wiring I.e nipped cable in box etc creating a existing fault on system once all the appliances are plugged in could just be cresting enough leakage to trip rcd. Had that one before, customer had used a 16mm back box whilst adding a new socket in kiddies bedroom!!! and cables were pushed against it! I came along changed d.b and found the fault 5 hours later! Pulling my hair out!
     
  13. trev
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    trev Regular EF Member

    It's either N-E fault in which case a simple global test will show it up and you can narrow it down to a circuit from there or it's a borrowed neutral, in which case a simple test will show it up.
    Borrowed neutrals are usually on the landing light in my experience, should be an easy one to sort mate.
     
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  14. brizospark
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    brizospark Electrician's Arms

    Location:
    Kent
    What's confusing me is why when I plug anything into kitchen socket covered by RCD A is it tripping RCD B? Surely this means it can't be a N to E fault as it would trip RCD B if this was the case
     
  15. brizospark
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    brizospark Electrician's Arms

    Location:
    Kent
    Can anyone explain that?
     
  16. SJD
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    SJD Trusted Advisor

    Location:
    Braccan heal
    I'd also suggest neutral to earth fault somewhere, and not necessarily on the circuits on the problematic RCD.
     
  17. sledgehammer
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    sledgehammer Regular EF Member

    Location:
    Swindon
    If its pme n-earth fault would common out both neutrals. I've had had exactly what you're talking about many times and its n-e.
     
  18. wersolaruk
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    wersolaruk Regular EF Member

    Could there be a borrowed neutral at that kitchen socket itself. Turn the rcd off covering that socket and turn other rcd on. Test between n-e at the problematic socket and if its showing voltage to earth it's a borrowed neutral! Sounds like a fault I would love to find!
     
  19. Brightspark2
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    Brightspark2 Electrician's Arms

    Location:
    North West
    Nice avatar :smartass2:....
     
  20. brizospark
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    brizospark Electrician's Arms

    Location:
    Kent
    It's not just this kitchen socket it is any socket in house covered by either RCD
     
  21. Richard Burns
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    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    If you have an NE fault on a circuit on one RCD then loading a circuit on the other RCD can cause the first RCD to trip.
    Did a diagram for you:
    RCD Trip due to other side loading.jpg
     
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  22. wersolaruk
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    wersolaruk Regular EF Member

    You have a n-e fault, megger everything buddy! All fronts off etc, good luck with it mate!
     
  23. shockboy
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    shockboy New EF Member

    Location:
    manchester
    try lighting common fault landing light 2way neutral on upstairs circuit feed took from downstairs ciruit
     
  24. markythesparky
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    markythesparky Electrician's Arms

    Location:
    Surrey
    If its a borrowed neutral then how did it test out ok?
     
  25. bigspark17
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    bigspark17 Electrician's Arms

    Location:
    wales
    Borrowed neutral on light circuits.! Put all lights on same rcd and try.!
     
  26. trev
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    trev Regular EF Member

    Or check to see if there really is one, locate it and eliminate it.
     
  27. Engineer54
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    Engineer54 Guest

    Every time we get a thread about RCD's tripping after a CU change, the common consensus is either a N-E fault or a shared/borrowed neutral. And every single time the OP has failed to test the installation prior to replacing the old rewirable CU with one containing at least two RCD's.

    How many more times do these guy's NEED to be told to test these installations before they start changing them out for god's sake??

    What's more, why is this fault causing such a problem to find and rectify. I would have thought that in around an hour, an experienced electrician would have sorted this problem out, ...or at the very least well on his way to finishing off any remedial work...
     
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  28. markc123
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    markc123 Trusted Advisor

    Location:
    Yorkshire.
    :shame: that's where i've been going wrong.

    Wondered where my afro had come from.
     
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  29. brizospark
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    brizospark Electrician's Arms

    Location:
    Kent
    Eng54 do you honestly think in the real world customers would give the go ahead to carry out testing before changing a board? This would mean an additional cost on top of a board change The customer would simply get someone else to do the job!
     
  30. trev
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    trev Regular EF Member

    A test for borrowed neutrals plus an IR plus an EFLI wouldn't take very long at all would it?
    You've already done enough there to identify any major problems and you're doing the rest of the tests anyway on completion of the change so what's the problem?
     
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  31. marcusone
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    marcusone Electrician's Arms

    Location:
    Bristol
    Its not an additional cost. Its part of the cost of doing the job right from the start. Not every customer wants it cheap, most want it done once and done right.
     
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  32. Guest111
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    Guest111 Guest

    The problem you know have is a potentially peed off client,did you leave them without power last night? And possibly a lot more work to do if it's not a quick fix,if you test thoroughly before swapping the board any issues will be found and corrective action and any further costs can be discussed with client.
     
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  33. Engineer54
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    Engineer54 Guest

    What do you mean extra cost?? The Minimal IR/ELI/Shared Neutral tests are for ''YOUR'' benefit, so that you know, or are aware of any problems, (such as you have now) before you start!! Armed with that information, you can advise your customer of any extra costs that will be associated with the board change!!
     
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  34. GLENNSPARK
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    GLENNSPARK Electrician's Arms

    Location:
    west yorks.
    eh...?
    its on the socket....
     
  35. GLENNSPARK
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    GLENNSPARK Electrician's Arms

    Location:
    west yorks.
    what a bunch of old twaddle this is...

    having read all this its clear to me you are not competant to carry out board changes....

    leave such stuff alone until you have gained the necessary experience
     
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  36. Sharpend
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    Sharpend Regular EF Member

    Location:
    Uk
    Brizo, no disrespect but you may need to shadow a more experienced spark, if not to improve your knowledge, them to learn the correct proceedure and why it's correct.
    Are you fresh out of training?
     
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  37. SJD
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    SJD Trusted Advisor

    Location:
    Braccan heal
    When you have completed the CU install, you will have a completed test sheet with the test data for each circuit (I hope), so you can just as well do some of that testing before doing anything to the old board, just in case it throws up things like N-E faults, or broken rings etc. There is minimal extra cost, but potentially saving a lot of embarrassment.
     
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  38. Guitarist
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    Guitarist Trusted Advisor

    Location:
    Norfolk
    I have to agree with Eng here. Basic tests at the time of quoting take 20 mins tops, and save a world of pain down the line. Also, the added bonus of carrying out a few basic tests gives you time to chat to the client and show them your shiney MFT. They get to know you, see that you are competent, and will usually give you the go-ahead there and then. Much better than someone who pops in for 2 minutes, gives a rough quote, then adds to the bill later on when the issues raise their ugly head.
     
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  39. Brightspark2
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    Brightspark2 Electrician's Arms

    Location:
    North West
    I know it's like an echo now but I agree with the above comments, testing should be done before you change the DB. I wouldn't change one without testing otherwise it just comes back to bite you like this. Then the customer rolls the old "well it was fine before".
     
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  40. Chris sparky
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    Chris sparky Regular EF Member

    Location:
    Hants
    Same as this. If they have had a quote off another "sparks" who's cheaper because he is going to lash it on and hope for the best, then let em do it. You may well get the call when it goes tits up :smug:
     
  41. GLENNSPARK
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    GLENNSPARK Electrician's Arms

    Location:
    west yorks.
    pervert...
     
  42. Knobhead
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    Knobhead Guest


    So once again we have a 5WW showing the vast depth of their knowledge (stupidity).

    You won’t do any pre-testing because it’s going to take time. Time that you have to spend later when things don’t work as they should! If I was the customer, my reaction would be quite rightly “it worked before you messed about with things” I wouldn’t pay you for any extra work because I would think you were pulling a fast one.
     
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  43. wirepuller
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    wirepuller Trusted Advisor

    Location:
    south uk
    We dont pre-test where a client has asked for a quote for a cu change,a visual is enough to see if there are likely to be problems and it is made clear in the quote that full tests will be carried out and problems may incur extra cost. I'd agree that an IR test prior to quoting would be a good idea,but even if the IR is ok what about continuity?...ring continuity?...problems here will still need sorting and wont be apparent unless full testing is carried out.I'm not going to spend time doing a full set of tests for a quote I might not even get.
    I can honestly state that problems encountered on my CU changes only ever take an hour or two to sort.Only on one occasion did we come unstuck,an apparently unmolested installation turned out to be big time DIY'd,IR faults-breaks in ring continuity-all earths cut off at JB's under floor.Took 2 days to sort,luckily client was able to witness the carnage and was amenable to sorting it.....clearly though this is one where we were wide open to the 'test before quoting' school of thought! It is clear that the OP does not understand testing and fault finding and is out of his depth,this sounds like a simple fault....whats the betting these RCD's get bypassed and he walks?
     
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  44. Kate
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    Kate Trusted Advisor

    Location:
    Bristol
    When asked to do fuseboard change I make it crystal clear to the customer that I have to check existing electrics beforehand. Any faults found would incur extra costs.
     
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  45. GLENNSPARK
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    GLENNSPARK Electrician's Arms

    Location:
    west yorks.
    often the case..
    i was on a board change over in Bradford yesterday....there were 2 existing circuits that had no chance whatsoever of going into that new board....
    i didn`t bother testing them....failed visual they did...
     

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