RCD tripping

[devlin10]

Ok before i start i aint totally clued up on electrical jargon and my
domestic electrical knowledge is limited, so please bear with me.

Was at my mums house when her RCD tripped. I isolated all the 3 MCB's. 1 for the garage, one for sockets and one that was labelled cooker.

I turned each one on individually and when i switched the cooker one the RCD would trip but not the MCB.The only way i could reset the RCD is by turning the MCB labelled cooker off.

I found that the dishwasher, washing machine, hob, fridge and extractor fan were all off this MCB. I unplugged all the appliances and tried to reset the MCB but as soon as i did this the RCD tripped.

Anyone have any idea what the problem could be. My only other concern is that there is another appliance wired into this circuit that i couldn't isolate. Their kitchen has been totally re done and to be honest i think the wiring is a complete disgrace.

 

[devlin10]

ok just spoke to my mum on the phone and she said she has rest the MCB and all the RCD has not tripped. all appliances are working now apart from the cooker. the display and controls for cooker are on but actual cooker aint coming on.
could a problem with the heating element cause the RCD to trip? if so why has the problem suddenly disappear?

 

[electronicsuk]

It is common for old/failed appliances with heating elements to cause an RCD to trip. Sometimes they simply become 'leaky' and, along with leakage current from other appliances, it's just enough to trip out a 30mA RCD.

In your case it sounds like you may have had a complete failure of one of the heating elements, or possibly (but perhaps less likely) the control circuit. The fault could have gone away because of internal protection built into the hob, or because successive application of power has blown the fault away.

In any case, from the information you have provided it seems like the hob is at fault. It should be isolated immediately, and remain so until it is either repaired or replaced.

I'd also be very concerned about the other appliances on the circuit. Electric hobs usually take fairly large amounts of current, and yet your description seems to suggest that it is simply plugged in? I assume what you actually meant was that there are sockets for the other appliances, but the hob is hardwired? If the latter is the case, the hob should be on its own radial circuit, and I would be suspicious if the kitchen fitters have made any further additions to this circuit. Would advise getting in an electrician to inspect the work, if you do it now then you may be able to bring action against the company that fitted the kitchen if the work proves to be of a poor standard.

What's the betting the main bonding also isn't up to scratch?

 

[Space cat]

By 'cooker' do you mean a complete, full sized cooker with hob, grill and oven? This should certainly have an MCB all to itself, generally bigger than 32 amps. What size is yours? If it IS bigger than 32 amps the case is cut and dried. Those sockets shouldn't be fed from it so get that bunch of cowboy kitchen fitters back. If you need advice on this go to the council, and the CAB too. They're free. Call Ghostbusters if you have to. Your wiring is indeed a disgrace.

Alternatively --

Is this a 'portable' cooker with one or two rings and a 13 amp plug? Or is it an electric oven which can also be plugged into a 13 amp socket or fed from an FCU? Either way, the breaker should be a 32 amp one and, if it is, the wiring may be up to standard.

I use the words "up to standard" in the way some electricians would, ie "it complies with the regulations" even though it's an ugly mess! This will make it a bit harder to get it done properly but you still have rights. When you pay for a fitted kitchen you expect a reasonable standard of workmanship. I find the word WATCHDOG to be very effective in such cases!