rcds tripping

11 Jan 2004
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United Kingdom
If you are getting strange issues with the RCD(s), the solution is easy.

Disconnect a circuit COMPLETELY from the board and retest. If the result is the same, reconnect and move on to the next. Continue until you find a circuit that, when disconnected, sorts out the problem. Then you know that circuit is faulty, causing the strange behaviour. Then when you have ID'd the culprit, you can then investigate to see what the problem is.

But you should test IR @ 500V. Just test LN to E.

And don't just disassociate "the usual culprits": disconnect ALL loads from circuits, just leaving the fixed wiring and accessories in circuit.
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ok problem found and sorted!!

it was found that a lovely plumber chap had used twin and earth to run the connections between the boiler and the controller. He then realised that he needs switched live, so instead of using 3 core he just used the tein and earth and pinched the earth from the immersion heater circuit!! i say pinched rather than borrow as im sure there was no intention to return it!!

the thing that stumped me was, the fault appeared to be on the utility circuit as when this was on it was tripping...so disconnected and seemed to sort the problem. But and a big but the washing machine was on the utility circuit, and im guessing was at the point of its cycle when it needed hot water and of course turned the boiler on!!! hense the trip!! so when i disconnected the circuit all i did was stop the washer drawing hot water, then later whenever someone used hot water it would trip!! very frustrating!!!

thanks for all your help everyone, and if anyone else gets the same problems hope this helps!!!
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16 Feb 2007
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West Midlands
United Kingdom
easiest way to find a shared neutral?

switch any 2 way switching on before turning the power off to ensure that the lights are on.
ensure at least 1 regular filament lamp on each lighting circuit and switch that one on..

turn the power off ( dur.. )

disconnect and seperate all of the neutrals ( remember to id them so you don't mix them up later.. )

switch off all the breakers ( or you'll read through the busbar.. )

then with all the lights switches on ( and shorting plugs in the sockets, short between L-N, usefull for some tests.. ), "bell" between one live and all the other lives.. if you get continuity or a low reading then it's going out the live, through the shared neutral and back up the other live..

move down one in the board and bell to the other lives and repeat until you've belled every live to every other live..

reconnect the neutrals and remove any linking plugs before turning the power back on..

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