Electrical - power cuts - why?

[John Smith]

Hi, Anyone advise on this one?....

Since about 6 months ago about every 10 days or so our house power goes off...how to establish why?

We have a main board with lighting and power switches...the problem is on the power side - its the power RCD that trips out.... There are 5 MCB's for cooker, heater and power sockets covered by the RCD. Some few weeks ago a friend checked out the system with some special kit he plugged into a socket outlet and said the 80Amp/30mA RDC was tripping at about 18mA...so replaced the RCD ...thought that that would resolve it...but no.

So the question is...anyone know of any easy...or even not easy ways of finding out why the damned switch trips?..

BTW this occurs when we are at home ...usually at nigh time....or away from home, on hols.

Thanks, John

[Jim Gregory]

Your RCD is doing its job. You have a hidden intermittent short to E. Isolate the non-rings and just test each ring. Check wiring inside all your buried or surface boxes as there may be a tiniest tendency for a bare L or N to short to E or metalwork. This was happening at random on one of our ring-main 2-gang power outlets, until I tracked the culprit down. Jim

[Palindr☻me]

OK, so you have a fault or faults. Either in the wiring infrastructure of your house or in something connected to it - or both.

You really need test equipment to do the job properly but, without it, you may be able to track the problem down.

There can't be that much powered up at night - particularly after you have eliminated double insulated things like bedside clocks. You should be able to eliminate most of them by actually unplugging or switching them off at night. If it never trips after you do that - you will know that it is one or more of them and you can find which by a process of elimination.

If it still trips, then it sounds like infrastructure.

Any signs of any missing slates, water leaks, etc? It could be water finding its way into a socket box or other place with potentially bare wires. Any sockets in potentially damp places? Any extension leads where the ends might get damp?

Have you taken any sockets off and put them back, for decorating, for instance? It may be you have damaged the insulation of the cable when screwing the box back to the wall. Easily done.

You could put the power off and look at every single place where bare connectors exist - like sockets, fused outlets, etc. If every one of those is fine, then it is either the distribution box or one of the appliances. Be careful, if you take a socket off the wall, that you don't damage the wires when you screw it back on!

[John Smith]

Ok, many thanks for advice.

[John Smith]

Thanks for that...useful advice. One thing you mentioned...ref ..

"There can't be that much powered up at night - particularly after you

...can you expand >> Hi, Anyone advise on this one?....

[Palindr☻me]

The trip operates because some of the current that should be returning to the supply is returning via the earth connection rather than the neutral wire. A double insulated device has no earth so cannot, generally, leak current to it, even if faulty. There are exceptions - eg, if you drop it in a full bath, have a mouse eat through the cable insulation, etc. But those things should be fairly easy to detect! So your clock may be useful for taking the blame for arriving late for work, but you probably won't be able to pin the trips on it..

If you can't establish a pattern to the trips and link that to a particular piece of equipment switching at that time (eg electric water heater on a time switch) and you haven't been doing any DIY near cables or outlets, then, I reckon water is in the frame. It comes and goes, whereas most things come and stay. Mind you, I live in a solid stone house with no dpc and so damp is a constant worry..

[John Smith]

[G Cadman]

Once you have tried all the below, i.e turning as much stuff off as possible over night. You could then get a competent person to come and put a RCD on each circuit in turn on you distribution box. If this RCD is more sensitive than the main one, you can find the circuit that is causing the trip, and narrow down your search. Electricians carry equipment that can test these circuits anyway, so they should be able to find if you have a trapped wire. In the past I have found a lot of these to be trapped or 'nipped' wires in the back boxes of sockets. The relavance of night time could be linked to the house cooling down and contracting. Or not, depending on your fault.

Regards G

[John Smith]

OK, TVM G. J