RCD TRIPPING

[srekcins]

First of all I apologize for the lack of model numbers/fuse ratings but I am currently at work and will update when I get home this afternoon.

When I moved into my current house in July 2004 we had a new fuse box installed with individual circuit breakers on each fuse and a main RCD which appears to only affect the upstairs/downstairs circuits. A couple of times since Christmas the main RCD has tripped for what appears to the untrained eye to be no reason whatsoever. My immediate concern is that there might be a problem with the plug sockets but neither of the fuses for these trip out. I know the power is not being cut completely as the clock on the cooker, which is on it's own individual circuit, is not resetting to default.

Before I update this with model numbers etc, is there anyone out there who can give some advice to put my mind at ease?

 

[thompsk]

It could be a few things, more likely than not you have a faulty appliance, when it trips again unplug everything - reset your rcd if it resets ok then you probably do have a faulty appliance, if on the other hand it trips when nothing is plugged in then that would indicate a wiring fault or rcd fault eitherway with this type of fault you need a qualified inspection engineer to get to the bottom of the problem.

 

[JohnD]

unplug all appliances. those that have no plug, the wall switch will (if modern) be dual-pole (you have to isolate both the phase and the neutral as an earth fault can be either of them).

if that stops it, plug half of them in for one day, and the other half the next day

it is most likely a watery appliance - washine machine, kettle, steam-irin, boiler, CH pump, electric shower etc
or something that sholdn't be watery but is - outside lamp or socket with rainwater in it, electic fountain leaking.

if you are unlucky, it will not be a single fault, but several very small ones, which together add up to enough to cause a trip.

if it happens when you are all out or at night it might be a mouse chewing on a cable.

 

[Space cat]

First things first, the function of an RCD is to check that all the current going out through the live wire returns through the neutral wire. The idea is to detect leakage to earth (or another circuit). The ring main fuses only trip on an overload.

Intermittent faults can be an absolute pig to track down. (I know that because I'm working on one right now and I can't even simulated the fault. ) Next time it happens, take careful note of everything that's plugged in and whether or not it's switched on. Do the lights also go off? Anything that goes off when it trips is a suspect so note its on/off status.

Prime suspects include anything with a heating element. These can easily develop leakage to earth as the insulation degrades. The silliest cause I ever saw was a toaster with a burnt breadcrumb wedged between the element and the casing!

 

[zappa]

I had one that was the oven grill, but only after it had got to a certain temperature after about 10 minutes.....