I've recently been rewiring some bathroom lights. Had all the cabling complete, had tested teh lights and the new fan successfully and was just tidying up and making good when (overnight) the ring main (rcd) breaker tripped. It now keeps tripping either when the boiler is turned on at the spur or if the boiler manages to stay powered, then it trips the rcd when it becomes active overnight. At no point has the lighting circuit tripped. I've tested tuning on the boiler spur with the lighting circuit (the one I was working with) both on and off. Same result boiler trips the rcd. Can I be fairly confident that there is nothing I can have done with the lighting circuit that would affect the ring main...and it's just an unfortunate coincidence? I'm concenred about a neutral / earth leakage but even as little as I know about it...feel that it's unlikely to be possible cross circuits?
So if I read this right, you've got a single RCD that provides power to the various circuits (boiler, lights etc) each on their own MCB? If you are confident about doing this, you could disconnect all circuits except the boiler at the live (via the MCB, turn them off) and neutrals (disconnect neutral wire for each circuit). That just leaves the boiler circuit intact. If it still trips, you know its the boiler circuit. If not, then connect one neutral at a time (starting with the lighting circuit) and see when it starts tripping.
Thanks for your reply. The only breaker labled RCD is the one controlling the ring main (32). The RCD that trips is not related to the lighting circuit. The lights are on a separate (6) breaker. I've tried the laymans version of your suggestion by simply turning of all the breakers and then tuning them on one by one...the only one that trips is the ring main RCD. And that only trips whe the boiler is turned on at its spur. I'm not confident at dealing with physically dicsonnecting the breakers or their cables. Might be time to get a sparky in.
as little as I know about it*. . . . <-----------------there lies the problem. .needs a full blown set of tests to determine what you have done wrong
Yes Commonly it is problems with the neutral wire in lighting circuits. Particularity when shared neutrals are in place.
Had a similar problem, The RCD was tripping when we were putting the boiler on so you would of thought it was the boiler. Turns out a previous electrician had connected wrong in to the lights. Now this fault was showing up only when the boiler was in play. I tried at the time investigating at the time in to everything. Just couldn't find it. Got a sparks in and he found the fault with his tester. I can't remember exactly but I think a neutral was in the Earth. Do what peter says disconnect
The lighting circuit doesn't need to be even energised as the neutral is causing it to trip the RCD. Need to disconnect.
i hear that try working on a circuit with an mcb off and you will find that if netural and earth touch the rcd trips
yea total pain when you switch off the mcb of the circuit your working on and dam rcd still trips (as the current that leaks from netural to earth via that circuit is minimal) also found that all rcd (din rail mounted) no matter the rated trip curent (or tested l to e trip speed) they all seam to trip the same speed under n to e fault
Thanks everyone for your help and input. I've got good news -> bad news -> good news -> bad news Good news : The ring main rcd seems to have stopped tripping with the boiler since I replaced the 20 yr old heating timer controller (on advice from a sparky). Bad news: I do indeed detect continuity between N and E circuits in the bathroom where I've been working. Good news: It is not my wiring that is at fault (following a disconnect). There is some continuity on the N E feeding the whole room. Bad news: I will have to trace the cause of the issue and it may well be something I've done in another area of the house... Think I'm getting a sparky to help with this one though.
When I worked on eastern leech years ago, I got called to a no supply! Found a remote RCD feeding a submain. This supply was for a class of electrical trainees. Bloke who called it in was the course tutor.they had Ben testing on boards and he said that the mcbs where turned off. Didn't know about the N-E fault!!! Trainer!!!!!!
Neutral and earth are connected at the supply transformer, so depending on your incoming supply type you may well be measuring that. Turn off the supply to the consumer unit and disconnect the main incoming earth from the earth terminal and test again. Don't forget to reconnect the main earth again before switching the power back on. Kind regards
i didnt till that happened no atm im no spark (least not trained) as most i had worked on either had no rcd or elb
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