RCD tripped

Head_The_Ball

Hi, we returned from a week away (Thursday to Thursday) last night to find that something had tripped the 80 amp RCD in our consumer unit that monitors both ring main circuits.

It was the 80 amp RCD, marked 'RCD Switch Test Monthly' (third from the left) that tripped. See the pictures. Neither of the 32 amp switches to the left of that tripped. Is that because they are less sensitive than the 30 mA of the 80 amp RCD?





(Ignore the burglar alarm switch. That is always off as there is nothing on that circuit)

We reset the RCD and everything appears to be working normally.

We cannot identify the source of any problem. Before we left we switched off most 13 amp sockets to items such as clock radios, table lights, toaster etc. leaving only a Sky+ box, a Humax recorder and two fridge freezers on. Also left connected but switched off at the machine were a dishwasher, a microwave oven and a washing machine. There is also an outside garden double socket that is a spur from a dining room socket but nothing is connected to that outside.

We have two completely defrosted fridge freezers (thankfully we have insurance for that) but fortunately our boiler is on a separate circuit so the heating was still working.

Checking our Sky+ box failed recordings showed that the power cut occurred sometime between 11:00 Friday pm and 8:00 Sunday pm so the power had been off for at least 94 hours and possibly a lot longer.

I suppose it isn't possible to ever find out what caused the problem, unless it happens again and we can identify the culprit, but we are puzzled as we have never had the RCD trip before. We are also puzzled why the 80 amp RCD tripped and not the RCD on the circuit that had the problem.

Any suggestions what we should do?

Forget about it and hope it doesn't happen again?

Have the electrics checked by a qualified electrician?

Something else?

Thanks

macman

Was the heating off? If so, I'd suspect maybe cold/damp/moisture causing the RCD to trip during the night, when the temp was lowest.
At the very least, I'd change the RCD to avoid any repetition.

Head_The_Ball

macman wrote: »

Was the heating off? If so, I'd suspect maybe cold/damp/moisture causing the RCD to trip during the night, when the temp was lowest.
At the very least, I'd change the RCD to avoid any repetition.

The heating was on with the hall thermostat set to about 12 degrees so the house should not have got colder than that.

However that does not affect the consumer unit which is in an unheated integral garage and is on an external wall a few feet from the un-insulated metal garage door so it has been subjected to low temperatures and varying levels of humidity every winter since the house was built about 13 years ago.

YorkshireBoy

Head_The_Ball wrote: »

We are also puzzled why the 80 amp RCD tripped and not the RCD on the circuit that had the problem.

The 2 devices to the left of the RCD are MCBs, not RCDs. You have damp somewhere. Are either of the freezers outside, ie garage or outbuilding? Otherwise get the outdoor socket outlet checked out.

Risteard

macman wrote: »

At the very least, I'd change the RCD to avoid any repetition.

Why? It's only doing its job.

Heedtheadvice

^^^ as per Risteard.
Time to be concerned is when the RCD does not trip when it should be doing. Hence the reason for the test button!

It would seem likely that some dampness affected the insulation between live or neutral and the earth wiring causing some leakage whilst you were away and thus a trip. Possible prime area for that is the outside spur but other locations cannot be ruled out.

Two options:
assume it may now be dry and monitor for a while (do test the RCD with its switch at some time) or
have an electrician test the circuits. The latter is really the best option though not the cheapest but may now not show up a problem.

In the longer term it may well be better to have a separate RCD for the outside spur to reduce the nuisance caused by the main RCD tripping when that spur has a problem.