New home - RCD tripping

pinkpixie_2

HiI wondered if anyone had had any experience of an RCD tripping. We moved into our new home early in November and for a few weeks the RCD tripped about every 3 days. We weren't doing anything the same any of the times and it seemed pretty random. We then unplugged the tumble dryer and video (for other reasons) and it stopped tripping. Feeling pretty confident, we assumed the problem had been sorted by unplugging one of these appliances but sure enough two weeks after the last trip, at the weekend it tripped in the morning - three times.We have no idea what this is and have been quoted £120 for someone to come out and investigate and then to quote for repairs on top of that. We're a bit loathe to do this yet and wonder if anyone has any experience of this?We've tried unplugging different things and looking for patterns but there are none. We can just be sitting watching TV and not moving and it happens.Should we get an electrician out? What's a reasonable price to pay for the initial visit? Someone's suggested calling the energy supplier as they had an experience of RCD tripping that was external to their house.Any advice gratefully received as our fridge freezer is on the same circuit and we're worried our food will defrost and be wasted if we don't spot it in time or are out for a long while.Thanks in advance.Pink Pixie

Avoriaz

Is it the main RCD or an individual RCD that is tripping?

They can be over sensitive sometimes but it could also indicate a fault on an electric fitting or the wiring so you must establish the cause.

If it is an individual RCD, try swapping two of the same rating and see what happens. Or buy a new one and try that. They are not very expensive. Also ensure that the problem RCD is the correct rating for the devices it protects. Maybe a higher rating RCD would solve the problem but do ensure you know what you are doing..

Basically it comes down to a careful and methodical step by step process of testing and eliminating all the possible causes until you find out the cause.

Enquire at your local authority or electricity board and see if they offer a free electrical safety check. Then, when the electrician is on site, pump him for advice.

Good luck.

pinkpixie_2

Thanks for your reply. It's the main RCD for the sockets. It's in a box in the kitchen, there are lots of different switches for sockets, lights, and other circuits. We've tried all the main (and lesser) contenders now and think we're going to need to ask for external help.Anyone have an opinion on this £120 call out charge?Pink Pixie

Avoriaz

£120 sounds a bit excessive for a call out charge though I have nothing to compare it with so maybe it is average.

Do try getting a free electrical health check from your electricity supplier or local authority.

Unfortunately your problem could be something very simple but it could also indicate a potentially serious wiring or device fault.

My knowledge is fairly limited but I think the most likely cause is that some inductive device that switches itself on and off intermittently is causing the problem. An inductive device (some electric motors for example) pulls a very heavy initial current load for a few fractions of a second before they settle down to their normal current demand. This can be enough to trigger a sensitive RCD although these should be able to differentiate between a heavy load and an unbalanced load. An RCD (as far as I know) measures any difference between electrical potential on the live and neutral. If there is a difference this indicates a fault so the RCD trips the circuit breaker.

It could be your washing machine when it spins, a vacuum cleaner, a tumble dryer or anything else with an electric motor.

Try along those lines but it is also possible that I am talking absolute rubbish so hopefully some knowledgeable sparky will post.

moonrakerz

I would have thought £120 was a bit steep for a call out charge - does that include any investigation time as well, if so how much. It's always worth ringing someone else for a second quote.

Canucklehead

Hi
When you say new home do you mean newly built?
When the RCD trips does it just trip the power circuit? (leaving you with lights)
Do you have any power points outside? If yes then perhaps it/they are not sealed properly .
£120 is perhaps on the high side more like £60 -70 . But you have a definite problem so it could take some time to pin down the problem by testing etc.
How long is a piece of string?
Good luck

Corgi Guy.

uncle_buck_3

Hang on a moment!

There seems to be a bit of confusion here about MCB’s & RCD’s

An MCB is a form of fuse (protective device) which overcomes the traditional problem associated with fuses in so much as when one blows it does not need to be replaced as a fuse does. MCB's operate when they sense an overload, or over current, and become an automatic switch, turning off, or tripping, the MCB when it detects such an overload.
It looks something like this:
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A331830&ts=35322&id=20630


An RCD is a similar protective device which is different in two ways. Firstly it is connected to both the live and neutral wires in the consumer unit making it a double pole switch, whereas the MCB is only connected to the live side of the circuit. Secondly, rather than just detecting an overload of current, it detects the fault which causes the overload.
It looks something like this:
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=A331830&ts=35295&id=86990


Using the above information which item is it that is tripping?

mepone9

you should get your RCD tested for nuisance tripping. This where an RCD trips below its trip rating usually 30mA causing a nuisance.
Don't know about the call out fee but it seems a bit much.

Canucklehead

Sorry didn't see your other thread !!
Now I know it's not as new as I thought
Get a full test.

C.G.

HugoSP

If it's your RCD then it's worth calling someone out to test it for nuisance tripping.

The RCD picks up earth faults. An MCB picks up short circuits or overcurrent situations. Each fault is different.

If the house is not new then the wiring is probably at fault. Firstly does it look like the previous person may have done any DIY involving the electrics?

If it is the main RCD, the try switching off each ring main or circuit that is connected though it at a time for a day or so. Does it solve the problem when one of the circuits is off?

Once you've narrowed it down to one circuit - come back to us.

pinkpixie_2

Many many thanks for all your helpful posts.I'm afraid I can't tell the difference between the two pics uncle_buck, but what I'll do is show my dad your post at the weekend and ask his opinion.Can't see any electrics have been done, previous owners don't even seem to have painted in the 12 years they were there so unlikely they did any electrical work.Canucklehead, it just trips the sockets, not the lights. I think my DF said there were a couple of sockets outside. We've ruled out the washing machine, tumble dryer, ... it did trip once when vacuuming but that was the only occasion the vacuum was plugged in. There always seem to be different things plugged in when it happens and we've managed to rule every item out via this method. I suppose it could be an overloaded circuit at certain times...Sounds like we're going to have to take a deep breath, get another quote and get someone out... However, I will first try the electricity supplier and see if I can get a free health check...Thanks a million everyone, this is really helpful.Pink Pixie