Past week or so our electrical CU has been tripping out at frequent, yet seemingly random times throughout the day and night.
It's driving me nuts!
So, what causes the thing to trip out?
Why does the whole power go out at the main switch instead of tripping the individual switches?
Is it a case of getting an electrician in to diagnose?
thanks!
Is it a case of getting an electrician in to diagnose?
yes
Assuming you've got a differential circuit breaker then something somewhere is most likely losing a few milliamps to ground. You either call an electrician to find out where or start the elimination process yourself.
First thing is to check if you have got a differential circuit breaker and if it's working OK. Press the test button and it'll trip.
First thing is to check if you have got a differential circuit breaker and if it's working OK. Press the test button and it'll trip.
There's a test button on the CU?
Sounds like the RCD is tripping which means something has got an earth fault, the RCD will knock the whole board off, or sometimes half the board with the lights and fridge not protected by the RCD.
Odd times maybe central heating.
A partial short circuit to earth is the most obvious one.
Is the MCB an earth leakage unit (see below)
The CB on the far right is the RCD (residual current device), in essence is a hyper sensitive "fuse" and protects plug sockets.
Do you have any power outside, in a shed, these areas if you do are probably the obvious places where the problem might lie.
What Dobbo says. Sounds most likely to be the RCD tripping, in which case look to your fridge as being the most likely culprit.
(that's theft my friend!)
It's like this one - split way, I gather.
The switch on the far right and the yellow button (marked reset on ours) are in the middle. That's what trips out, not the whole power as the lights stay on.
If fridge, what to do about it?
(appreciating the replies folk 
)
There is a test button on every one I've seen (I live in France where they've been an obligatory fitting a lot longer than in the UK). There's also the word "differential" somewhere on all the ones I've seen. You'll normally have a big mains cable coming out of the ground, possibly some big fuses then a circuit breaker with a differential breaker integrated that feeds the rack of breakers/fuses that serve all the different circuits in your house. The test button is on the bit labeled "differential".
How often does it trip?
New fridge I'm afraid. Is it a few years old?
Basically, an RCD trips when it detects an imbalance between the current flowing out along the live and back along the neutral. If this is happening at random times during the day or night then the fridge is the most likely culprit - come across a few like this. Other common causes are steam irons and kettles but I'm guessing you don't run these round the clock!
If it's split way it rules out a lot of kit, could be anything on the ring main or other circuits. Immersion heater or heating? If it happens at night you can narrow it down some more. Try to get the fridge on a spur on the non-rcd side of the board so if you are away and it trips you don't come home to a stinking apocalypse meltdown!
OK, so it may be marked "residual and reset" rather than "differential and test". It's there to save your life if you touch live as it will trip at very low losses to ground.
I'm shocked 
to learn lighting circuits my not be connected.
Anyhow, if the differential/residual breaker is working then you need to find what's tripping it. Any appliance that uses water is the first place to look.
as above
Kettles, irons, water heater, electric shower and of course outside power supplies (even if not being used to power anything) as water ingress can cause a short circuit.
I had a power socket in a room next to a bathroom which had water leaking on to it from behind !!!!
Fridge is about 2 years old. Built in job, so would hate it to be that!
Central heating is a possibility as it's just got colder and only started happening - it could also coincide with the rads being put back on after decorating...
It's tripping 2 or 3 times a day (sometimes less), time is really random (eg. about 5am previously, 8pm and 11pm last night, 7:30 this morning, when I switched on the broadband - although that's the only time switching that on has tripped it!
we had a spate of random upstairs lighting trips even when the lights weren't on. Never did find the cause but it's not happened since we bought a new fridge. Don't ask any more as they were on different sides of the CU so what I've said above makes no sense what so ever. I just hope it was a dodgy bulb that's since been replaced.
Lighting circuits don't have to be rcd'd do they??
Of course, the RCD itself could have become a bit sensitive. They are designed to trip at no greater than 30mA inbalance current and usually tend to trip around 25mA when new (+/- a few mA). However, I have seen some trip at as low as 15mA, which coupled with a bit of 'normal' leakage from assorted appliances can be enough to set it off. Best get a spark in to do a ramp test on the RCD, as well as check out everything else.
Go over all your rads again and put bog roll under each connection to check for drips.
If your not sure get a sparks in, or perhaps if the CH system is on a plan of any kind get a man in.
As a sparks myself these things can be a bu&&er to find, but it makes sense to "back track" any jobs you have done (lifted floor boards and stuff)
Lighting circuits don't have to be rcd'd do they??
Not lighting circuits per se, but if any cables of said lighting circuits are buried less than 50mm into the walls and aren't protected by earthed steel conduit or similar (ie. the switch drops), then the circuit needs RCD protection as per 17th edition of BS7671. Earlier editions didn't stipulate this and there is no need to bring earlier installations up to the current standard for the sake of it.
Pretty simple really, just turn everything off, then turn things on until it trips. Make sure what you turn on start up fully, with the heating turn the settings up so to force it on and give it a few mins, to fully operate, it could be a valve or the ignition. Do until it trips then repair or replace fooked item!
Nice to see we've got a few sparkes on here. Any advice on fault finding if turning stuff on and off doesn't reveal a fault? I'd still like to find out why my upstrais lighting circuit used to trip randomly, even when off. It was so random, hand full of times a week and then nothing for months that I'm not really convinced the problem has gone away.
Great info chaps.
Going to check the central heating (plumber bloke did refit the rads, as he was coming to service the boiler anyway) as I have a feeling it coincides with the rads going back on. Could be wrong though!
Montylikesbeer has also reminded me that we have a few sockets hanging loose from the walls whilst decorating (have been like that longer than this prob has been going on). So I'll refit a few of those tonight (after my ride!).
All else fails I'll calls the guys who fitted our hall lights a couple of months ago to do a diag.
Onzadog - your problem sounds very much like mine. This was happening a year or so ago, but went away.
I'd still like to find out why my upstrais lighting circuit used to trip randomly, even when off.
You may have other things off it, bathroom fan, security alarm, etc.
Loose connection?
It might simply be a plug that where live or neutral have come loose and are touching ground. It could be a loose connection in the consumer unit or the unit could have a fault in the circuit. By law, you should have an electrician sort it out, but you might find the fault by simply examining the plugs in your home.
Has something new been plugged in recently? Are you maxing out a ring or spur?
By law? It's his house not a public place.
It's most unlikely to be a plug where live or neutral have come loose. It's most unlikely to be a loose connection.
Off the lighting circuit upstairs, we have the shaver socket in the bathroom (originally part of a different circuit when we moved in and not protected by the RCD, we swapped that over but that was a long time before the issues), the combi boiler and bathroom extractor run off that circuit as does a power socket in the loft which is not used for anything.
No alarms, doorbells,no fridges. It's tripped when we've been out of the house so the only thing that might draw a current while we're out is the boiler. But we've had spates in the warm summer months and colder winter times.
I'd even suspected a short in a celing rose that might move due to variation in temperature.
I also thought of splitting the ring into two lines to narrow down which light fitting/join it might be, but I can't replicate the fault so could be waiting several months between trips.
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