Please help

[BigRich]

Two nights ago our circuit breaker tripped, which tripped the main breaker and plunged the house into darkness

I left the problem circuit off a few hours and then switched it back on - all was ok for about 24 hours, it's now popped again, and I'm beginning to have my doubts regarding the problem socket. I've even swapped the circuit breaker to another 32 amp one, but the same problem arises.

I read the post thinking the MCB (circuit breaker) tripped first which then tripped the RCB (main breaker)

Rich, can you confirm if the 32amp MCB (breaker) has tripped (even once) or is it just the RCD (mains switch) that is tripping?

Right sorry: Chain of events is basically.

All MCDs are ON, and then the RCD trips. I then turn it on again, and it trips the RCD again (different intervals. Sometimes hours, usually seconds, sometimes minutes)

Now, if I turn off the 32amp MCB, and then energise the RCD, the RCD doesn't trip. That is why I think it's something on the 32amp MCB that is causing the RCD to trip. I've swapped the 32amp MCB with an identical unit and the same happens.

Does that make sense?

 

[Pensdown]

That make total sense and I did indeed read your post incorrectly.

John, you're right with the P-E fault

Now to try and find it.

If you're sure you've un-plugged every appliance then they are ruled out.

The damp socket could still be a problem so you could try removing the front and connecting the wires together in terminal block to eliminate the socket facia.

If your cooker has a mains switch turn it off.

If your immersion heater has a mains switch turn it off.

If you have any other fixed appliances turn them all off

It is a process of elimination and if you call a sparks out he will do the same. He will of course be a lot quicker as he will have some test kit.

 

[securespark]

If you're sure you've un-plugged every appliance then they are ruled out.

And if it does not have a plug, but a switch, switch it off.

Remember: boilers, pond pumps, kettles, immersion heaters, d/w's, w/m's, tumble dryers, external wiring, etc...

Finally, remember this:

I had a fault where energising a security floodlight circuit tripped the
RCD, even though that circuit was not on the split side...

It turned out there was an N/E fault on a socket.