Fuse trips when no lights in use

The message from Tim Westcott contains these words:

I would think that the most likely fault is a fault with the MCB itself. I may be wrong but I can't think of any fault condition outside the MCB that would not be at least as likely to trip the circuit when the lights were on as when they were off.

MCBs are easy enough to change if you know what you are doing but given that you think they are fuses you probably lack the ability to change one safely so get an electrician in.

For all I know messing about inside a consumer unit might be notifiable under Part P which should make the electrician the cheaper option.

In message , Roger writes

Mice or squirrels in the attic eating the cables? A squirrel just ate most of the insulation off some 10mm T&E in the roof space at work, a

If there are no lights on how do you know *exactly* when it trips. Could it be tripping when you switch a light on? Is there a bathroom fan on the circuit or a security light? You need to provide more info. The writing on the item that trips or a pic would be a start because as has already been pointed out its not a fuse.

Jim A

There is a bathroom fan on the circuit but that has not been on when the circuit breaker trips. The downstairs lights, electric sockets, etc are all on different circuits and all the circuit breakers are clearly labelled as to what the circuit is. I've heard it go a number of times - the consumer unit is in a cupboard which is rarely closed so it amplifies the sound to an audible level - and each time there has been no lights activated on the circuit. That is a certainty. There is no obvious action (eg turning a light elsewhere, etc) which causes it to happen. The unit itself is pretty much like the photo on the attached link - its a circuit breaker (B in the photo) that trips.

OK, that's a start, though I hesitate to encourage you too much if you are not sure how. The numbers written on the item that trips would be a help.

Regarding your last question be aware that a great deal of the lighting wiring will live even when the lights are off.

Jim A

Somebody may have wired another intermittently switching device onto the lighting circuit just for convenience, even though they shouldn't.

You need to leave the power to this circuit swiched off until you've fixed it. Leaving it reenergised overnight is really not a safe idea. This is one of the plusses of fuses.

NT

I don't mean to be rude (just trying to stress the importance) but, with this level of knowledge, you really need to get someone in. Someone who has a clue about mains wiring. At the very least, get a decent book about the subject from the library before trying to debug it any further yourself.

MBQ

I have no plans to deal with this myself!! I should have made that clearer I guess I have the electrician who fitted the consumer unit and did the wiring in the extension coming out to look at it on Friday.

Oddly enough, I reset the circuit breaker yesterday evening - so the kids didn't have to have a bath in the dark - and we've had no trips since.