RCD Tripping

Macy

Have a problem with the RCD tripping in the consumer unit. Thought originally it was the water pump, and then the kettle but it seems to be completely random - We can't make it trip so it doesn't seem to be appliance or a loading problem (it's happened over night). So any sparks give me advice on what/ where to look?

My plan is to check all the sockets for loose connections, but after that I wouldn't be too confident at checking the wiring at the consumer unit (and the actual RCD) but will get someone in if the sockets don't bring any joy. Is there anywhere else I should be checking? Only other thing I can think of is to check the wiring in the loft?

Hoagy

The RCD protects the socket and the immersion heater, so no point in looking in the loft.
Very unlikely to be a wiring fault, nearly always a faulty appliance, particularly the wet ones, such as the kettle.
If it happens in the middle on the night I would be taking a look at fridges and freezers.

Avns1s

I have a similar problem with and older type rcd. Only happens about once every two months or so. I have tried isolating various circuits and still the same. It would almost definitely happen with ligthening or any other surge on the ESB line in. But because it doesnt happen to often, its not worth making too much of a fuss.

Personally, I think it might just need a new RCD.

Macy

Hoagy wrote:

If it happens in the middle on the night I would be taking a look at fridges and freezers.

Yeah, well that's what we've got it down to as the only possible appliance, and of course the American Fridge Freezer has the water element too. Only happened once overnight, but it only seems to happen when we're home (hence we suspected the water pump), but i've run the water pump for an hour without it tripping which lead back to the fridge as we figured we'd be taking water/ice only when we're home.

We have a second fridge freezer, but I was hoping to avoid a spell with my Bulmers going warm, if we emptied the main fridge it to try and confirm it was that.

Hoagy

Emptying the fridge probably isn't necessary, if you can get a good look at the back and check there isn't a drain or something dripping onto the flex or the compressor or general dampness.
These faults can be a real pain to find. Sometimes there can be more than one cause. The RCD trips when the leakage current to earth reaches 30mA, which might be the sum of several smaller faults.
Usually a thorough visual inspection is what you need.

Macy

Cheers. Did try and look for moisture last night, but no joy. Will try again if that's a likely cause.

Macy

No joy on the moisture front, but then it didn't trip. Tried drawing off water and ice to make it trip no joy, so beginning to wonder again as to whether it's an appliance or a fault at the consumer unit. At this stage I think it's bite the bullet and get a sparks into investigate.

Hoagy

Sounds like a good idea.
Don't spend too much time trying to find the problem.
Consider fitting one or two more RCD's (or RCBO's) and dividing your circuits across them.That will narrow down the possibilities and also limit the inconvenience caused by the nuisance tripping.
If you're in the West of the County it might be ESB, we've been having brownouts regularly at night for the last few months.

towbar

Was looking over our wiring in new house and electrician has put fridge circuit on own MCB seperate from sockets and not on an RCD. Is this common practise?

Hoagy

Doesn't comply with the Wiring Rules unless the fridge is permanently connected.
All sockets must be protected by an RCD.

Mr Magnolia

OP, you could try knocking of a particular MCB for a day and see if it stops the tripping, the following day try a different MCB. Keep doing this until the RCD stops tripping. It could be a number of things really.
How old is the wiring and RCD?

Macy

Sparks400 wrote:

OP, you could try knocking of a particular MCB for a day and see if it stops the tripping, the following day try a different MCB. Keep doing this until the RCD stops tripping. It could be a number of things really.
How old is the wiring and RCD?

It's in a new build, well just under 18 months I assume that the RCD is new to.
Part of the problem is the seemingly random nature of - it hasn't tripped since the evening before I posted. Nothing different done, no great change in usuage, but some evenings it can trip 3 times and then go over a week with nothing - like I said, I don't seem to do anything to make it trip.

Avns1s

Macy wrote:

It's in a new build, well just under 18 months I assume that the RCD is new to.
Part of the problem is the seemingly random nature of - it hasn't tripped since the evening before I posted. Nothing different done, no great change in usuage, but some evenings it can trip 3 times and then go over a week with nothing - like I said, I don't seem to do anything to make it trip.

Do you have any exposed cables to outside lights, fountain, external socket, garden lights or other outside circuit that hasn't been wired up yet?? If you have a cable left for an outside light, it could be that it is getting wet from rain and this is what is tripping the circuit. If its dry, this won't happen maybe giving your periods of non tripping.

Macy

No exposed cabling outside. Doesn't seem to be weather related, probably be more in warmer weather but not exclusively either. Head wrecking is what it is.

Avns1s

I know what you mean. Unfortunately, I think you're down to the following:
1. Replace the rcd to determine (unlikely as it may be) that its not faulty.
2. Switch out the MCBs one at a time and try to narrow it down to a few sockets at least.
3. Live with it as annoying as it is!

Wish I could help more, but good luck and make sure you let us know if you do find it.

Mr Magnolia

Get an electrician in, there's some things they can look at... ie disconnecting the circuits and start meggering them. He/she will find the fault for you

Copper

Every appliance has a normal earth leakage, if its a big house and you have a lot of appliances plugged in, the RCD could trip because of the earth leakage exceeding 30mA. No single appliance is faulty, the RCD might be tripping because all the leakages add up. In that case you need several RCDs or RCBOs.

Make sure if you get an electrician that he doesn't;

1) Bypass the RCD, sometimes if the RCD is tripping and sparks can't find the fault, they will just bypass it which means you will have no protection, and you will never know the difference unless you check.
2) Put in a higher rated RCD (probably 100mA) so that it won't nuisance trip, this won't protect you adequately in the event of an electric shock.

http://www.etci.ie/safety/faq.html#RCDs

Macy

Cheers for that. Happened again a couple of times yesterday after being okay for a few days. The plan was to give the water pump it's own anyway (the sparks spotted it before) and I think I'll ask for the kitchen sockets (American Fridge Freezer, Dishwasher, Kettle etc) to have their own too. Should at the very least isolate the problem, if it's something other than build up of small leaks.

Thanks for the help, I'll post back how I get on and what was the cause/ solves it.

Spocker

Any solution to your problem Macy? I'm having the same type of issues (intermittent, no specific device seems to be at fault and very frustrating).

Is the general consensus to get a sparks in to trace it?

rogue-entity

Copper wrote:

Every appliance has a normal earth leakage..

I seriously doubt that. First, most household appliances are not connected to earth as they are double-insulated. Second, any leakage into earth indicates a problem with the device, the earth cable in devices connects to the metal casing of the device so that if one of the phase wires connects to this conductor, it would short-circuit through earth, the surge in current will blow the protection device (usually the RCD or ELCB, or a fuse). Only appliances not double-insulated AFAIK have to be connected to earth.

RCDs generally only protect the socket circuits, much in the same way the the common ELCB Tripswitches do. Other circuits like the lights, cooker, water pump, are normally connected straight to the live and neutral bars.