Tripping consumer unit

Garfeild · 25 Dec 2012

Hi all, I have a problem with my consumer unit tripping out.Typically,it started Xmas eve
I've narrowed it down to the kitchen circuit, when I try to turn the kitchen switch back on, the main switch will trip.
I have disconnected everything in the kitchen from all plug sockets including dishwasher and washing machine etc,and over Xmas have had to run extension leads from the hall to run the appliances.
The problem is,that even with everything unplugged the switch still trips,so what am I looking for?
I'm thinking possibly a live or neutral come adrift in a socket and touching where it shouldn't ? I don't think we've had mouse activity ( we've got 3 cats,they wouldn't dare)
Anything else I should be looking for,and what would be the best plan of attack?
TIA

Iggifer · 25 Dec 2012

have you unplugged your fridge/freezer? Or are these on a different circuit?

HERTS P&D · 25 Dec 2012

Does your hob have an electric ignitor on it?

If so unplug it and try and re-set your kitchen circuit.

Andy

Taylortwocities · 25 Dec 2012

Look at any place where water and electriciaty might meet.

Esp heating services, boilers etc. Also any outside lights, sockets, feeds to sheds etc.

These may be fed from your kitchen circuit but may not be obvious.

Luckyphil · 25 Dec 2012

Could even be Dampness in a Backbox , One I did recently was a Joint Box attached to a Gable End of a Kitchen Unit next to a Dishwasher , The humidity off the Dishwasher waste caused so much Condensation the JB was soaking , Had to redirect the Cables and reterminate with Crimps , time to think out of the Box so to speak ..... JB`s behind Kitchen Plinths are a Kitchen Fitters favourite !

Lucky

Greenie9657 · 25 Dec 2012

Hi mate.

That sounds like there is a straight path earth behind one of the sockets if youve disconnected everything. I'd start taking front plates off your sockets to see if any wires have popped out.

Garfeild · 25 Dec 2012

Everything in the kitchen is unplugged,the boiler and heating is fed from the airing cupboard upstairs and is still working ok.
The freezer is in the garage and is on a separate circuit.
I think tomorrow,I'll check all the switchplates for iffy connections.
Most of the wiring is surface run behind the cabinets there's only a couple of sections under the floor.

Greenie9657 · 25 Dec 2012

If its easy access,it might be worth visually inspecting as far as you can the exposed cable just in case something has crimped it by accident.

ban-all-sheds · 25 Dec 2012

Luckyphil said:
A post with a ludicrous number of spurious capital letters.

Why?

ericmark · 26 Dec 2012

A neutral - earth fault can give some misleading results. As the load is increased the voltage difference between neutral and earth also increases so just adding load can cause the RCD to trip. Which tends to make one blame the wrong item.

Step one look for any FCU's and switch off even with fuse removed they can cause problems must be switched off.

Unplug all items again even when not being used can cause a problem.

If not cured then it's a meter job to find earth neutral fault.

Garfeild · 26 Dec 2012

All visible wiring looks ok,all wires are secure in the switch plates can't find any obvious faults.
Can I disconnect and separate the wiring from one of the switchplates roughly half way round the kitchen effectively cutting the circuit in half,and see what happens then,or doesn't it work like that?

Taylortwocities · 26 Dec 2012

Yes, it does work like that.

The circuit is probably a ring, but first you need to confirm that it is.

You'll need some test equipment to do this.

Firstly you'll need a multimeter to check that the live, neutral and earth conductors are indeed intact and separate rings.
The first test is basic continuity. You must first do this to make sure there are no breaks in the ring, otherwise you'll lead yourself down the wrong path.

the next test is insulation test and you'll need a dedicated insulation tester to do this. The insulation test will tell you if there is any problems in a contact (however small) between the separate L N and earth conductors.

Once you have done this then the next step is to break the ring roughly in the middle and then carry out those tests again on the two separate halves. Hopefully then you can identify which half of teh ring is causing the issue and then narrow it down to the actual fault.

It is just possible to do this process without test equipment - using a hit and miss process - but it may be a long drawn out process. Also, you may end up with exposed live conductors, and that is not recommended!

EFLImpudence · 26 Dec 2012

Taylortwocities said:
Yes, it does work like that.

Only if you also disconnect at the CU.

Garfeild · 26 Dec 2012

It sounds a bit more involved than I thought,I was thinking I could split the circuit and see if it trips again.
It is on a ring,I'm a plumber,so tend to think of a flow and return situation,I know where the cables run,having done most of the donkey work myself when I fitted the kitchen(15 years ago,no problems until now)
So if I split the circuit,am I looking for OL between L-N-E
On both halves of the ring testing on the respective cables?

Chri5 · 26 Dec 2012

If you break the ring along the circuit, the fault will still be there, because both sides still return to the cu. if you take one set of the ring wires off the cu you creat a radial circuit.

Once you have the radial you can split that down and it should help you find what part of the wiring might be an issue.

It could be a faulty appliance, wiring, a socket or a fused spur.

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Tripping consumer unit

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