Electrical Fault

My RCCD trip yesterday evening and I have narrowed it down to the down stairs ring main but having unplugged everything it still trips. I have also disconnected the central heating and kitchen fan at the spur box but it still trips. That only leaves the built in oven which I think is connected by a spur so if it isn't that I am at a loss. I should be able to get to where the spur for the oven breaks out from the ring but I don't see why this should suddenly have gone as it wasn't in use at the time. I can only assume that the next course of action is to progressively disconnect sections of the ring between junction boxes to highlight where the fault lies? Is there anything else I should try before I call in a sparks?

Kevin

Reply to
Kev
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Depending on where the fault is, possibly irrelevant.

Remember that a N>E fault can also trip an RCD, so you need to disconnect/isolate both L and N when fault finding.

Owain

Reply to
Owain

Sounds like you're almost there. I would check insulation and proximity of L and N wiring in downstairs ring-main boxes and junctions in case one is inadvertently touching E. Also look for any water moisture or dampness seeping near bare conductors, which fault condition would trigger a tripping. Jim

Reply to
Jim Gregory

Might also simply be a socket fixing screw having finally gone through some insulation.

Andy

Reply to
Andy Cap

How did you 'narrow' it down? Simply switching off an MCB doesn't disable that circuit as far as an RCD is concerned - a neutral to earth fault will still trip it. The only way to truly disable the circuit is to disconnect line and neutral.

By far and away the likely cause is a faulty mineral insulated heating element. To be found in immersions, washing machines etc and ovens.

Reply to
Dave Plowman (News)

I flicked off each MCB then switched them on in turn, as soon as the down stairs ring mcb is switched the RCCD trips out. I must admit that I was surprised that it was the down stairs ring as it is usually a circuit for the garden with pond pumps that trips. Failing that it has always been the kettle or the wife's rice cooker so having disconnected everything I am puzzled why it still trips.

Kevin

Reply to
Kev

This effect can be deceptive.

I had a similr problem and thought that I had narrowed it down as well. As it turned out, the only only reason that the RCCD tripped was because of the MCB load suddenly appeared on the RCCD [and the load only needs to be marginally out of balance (before it settles) to trip out the RCCD!]

Thus giving a false impression.

There is no easy way without a megger (which is the way I did it in the end).

Cheers

Peter

Reply to
puffernutter

Dave Plowman (News) pretended :

Just to qualify that a little....

If the RCD can be made to reset by turning MCB's off, the one which does cause it to trip as it is turned on will most likely protect the circuit with the problem.

Reply to
Harry Bloomfield

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