RCD trips with various circuits on

AJ16 · May 1, 2015

The RCD tripped out 6am yesterday, I'm still trying to get an electrician to come so looking for advice meantime on what I can do.
There is one main board then another in our extension which is fed of an MCB in the main board.
The house light circuits are fine and don't trip the RCD, there are 5 other MCBs feeding the house power circuits, we can get 3 of them to stay on, but if we plug something in and switch on the RCD trips. We can't get the the 5th one to stay on, it's the upstairs ring in the house. Even if we leave the 5th MCB off the others will trip if we switch something on. The only one which doesn't seem to trip it is the cooker circuit. The extension MCB is ok most of the time so we have a couple of leads from sockets in there to feed the fridge in the house and the TV. Strangely sometimes this MCB won't reset unless we switch off all the other MCBs and switch on one by one.
As the RCD seems so 'trippy' I was wondering if they ever go wrong? It's a 63A one.

baldsparkies · May 1, 2015

Fault diagnosis for intermittent RCD tripping is best left to a competent electrician, on sight, with the knowledge and appropriate test equipment.
There are far to many variables to be able to give you any definitive or constructive advice over a website.
Getting a qualified electrician to diagnose the problem is the most constructive advice that can be given.
It will save you a lot of frustration.

Marvo · May 1, 2015

They do go faulty sometimes but it's highly unlikely that's the problem. When it comes to RCD tripping, without the specialized test equipment you're not going to be able to find the fault(s) so you'll have to wait for the sparky.

Richard Burns · May 1, 2015

You have already done the straightforward resolutions to this sort of problem.
I.e. switching off MCBs until the RCD holds, because this has not solved the problem it does become more complex to resolve.
It is likely that a diagnosis could be made fairly quickly on site but the resolution may be more difficult.

The only other option that may help, if the fault is in an appliance and not in the circuit, is to make sure that everything on the upstairs ring is unplugged, not just switched off. If there is a fault on a piece of equipment then this should resolve the problem (and possibly identify the faulty item), however I would be tending to expect this fault to be a circuit fault so this may not help.