RCD tripping, can't identify the appliance

battenburg88

Not really DIY (I won't be attempting any DIY electrics!) but hoping for some advice.

Our street had a power cut today for a few hours. I went out and when I came back realised that one of the RCD circuits had tripped. By turning off each circuit breaker one by one, i've narrowed it down to 'Sockets 2' downstairs. Annoyingly, this has both my boiler and fridge attached!

The boiler, a fancy light switch and the cooker hood are 'hardwired' i.e. they go into one of those chunky switches on the wall. I've turned all of those switches off which I hope is equivalent to unplugging them as I can't physically disconnect the cable. Everything else that I know to be on the circuit (washing machine and fridge) as unplugged, but the circuit is still tripping the RCD.

I have home emergency cover, but for electrics this seems to only cover "complete failure" of the power supply. It does cover loss of heating, and in this case my boiler is not working so I guess that applies. But I don't know if there is anything actually wrong with the boiler, so I don't know what happens if they come out and the boiler is fine - do they then just go home?! Or are they obliged to get my heating working again even if that involves some electricals.

All the while by freezer is defrosting and I have no heating! Any suggestions appreciated. Am I missing something on the circuit testing front?

kimwp

It's not a full solution, but have you got an extension cord to plug the fridge into a different socket? At least then you won't lose all the food.

battenburg88

Good shout. In the panic I hadn't thought about a simply and sensible thing like this!. I might just about have one long cable.

ThisIsWeird

You are right - these isolating switches should be double-pole, so cut both the live and neutral to the connected appliance, so any fault within the appliance shouldn't still cause a trip.
First obvious Q - are you 100% certain that there isn't something else plugged in, a phone charger, a modem, anything like that?
Meanwhile, as Kim says, power the important stuff via an extension lead.

battenburg88

I'm pretty confident that there is nothing else plugged in on the circuit - just done a loop to double check. Downstairs there are two socket circuits and the problematic one is for the sockets to the utility room and kitchen, so there aren't that many.

When I moved in quite some years ago I had an electrical safety check and that circuit actually ended up being replaced (all legit/certified etc.) because there was a fault and it was easier to just run a new cable through. 

So if those those fused switches being off effectively means that I have 'unplugged' the appliances, then what else could there be? Could the circuit breaker on the fusebox have broken? I realise that its not possible to diagnose on the MSE forum, but to save myself an electrician call out if I can. Does feel like I might not be able to blame it on the boiler though, which means no use for home emergency cover.

koalakoala

I once had a power cut which made my sky box not work at all.
my home insurance paid out for it

HHarry

I have seen slugs in the back of a socket causing an RCD to trip, so it may not be an appliance fault.

FreeBear

It could be a faulty RCD - I've had one in the past. Easy enough to swap out, but ONLY if you know what you are doing.

battenburg88

Ha, slugs are not beyond the realms of possibility in my kitchen!

Were it something like that though, it seems odd that it would be triggered by a power cut. Although having said that, i'm not an electrician so I don't really have any idea what would or wouldn't cause this.

Kiran

As stupid as it sounds, have you tried turning it off and on again? I had a faulty mcb that tripped the rcd. No idea why, but couldn't disconnect as everything as it was on the lighting circuit. Turned the circuit off and back on again and everything turned back on and no further tripping between then and having the mcb replaced 

ThisIsWeird

battenburg88 said:

I'm pretty confident that there is nothing else plugged in on the circuit - just done a loop to double check. Downstairs there are two socket circuits and the problematic one is for the sockets to the utility room and kitchen, so there aren't that many.

When I moved in quite some years ago I had an electrical safety check and that circuit actually ended up being replaced (all legit/certified etc.) because there was a fault and it was easier to just run a new cable through. 

So if those those fused switches being off effectively means that I have 'unplugged' the appliances, then what else could there be? Could the circuit breaker on the fusebox have broken? I realise that its not possible to diagnose on the MSE forum, but to save myself an electrician call out if I can. Does feel like I might not be able to blame it on the boiler though, which means no use for home emergency cover.

These fused switches should be DP, certainly the boiler's, but that doesn't mean they are. 
The hood and fancy light's FSUs could perhaps be SP, so only isolating the Live, and you can still get imbalances via the neutral and earth that can trip an RCD. But, that's just guesswork, and using SP units would be a cheap move (are they even available?!).
Could you explain what is actually tripping? A photo of your CU is always good, but is the tripping unit an MCB or an RCBO?