Light circuit tripping breaker

mattyfez

mattyfez

mattyfez

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12 Apr 2007
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But of a weird one.. Noticed my lights wouldn't turn on so I looked at the box and the breaker had tripped.
Flipped it back on but when trying a light switch 20mins later it's tripped again.
Here's the thing though.. There's no load on the light circuit both times... No lights on as I'm just watching TV with a mains powered table lamp in the lounge.

Very odd... How do I even begin to diagnose that!
 
Just to confirm, you mean the MCB tripped for the lights circuit and not the RCD?
Are you sure there is nothing else connected to the lighting circuit that could be the problem, e.g. extractor fans with an overrun timer? Do they have isolator switches?
 
Yeh..
It's just the individual breaker for the light circuit, not the main rcd..
Seems to be working now.. Weird.. Ive tried all the lights in the house and they are turning on and off fine..
Very strange..
 
Ah, I assumed you had meant it had already tripped before you tried to turn lights on.
If it's one switch that's causing the trip, then try taking out the relevant bulb(s) and see if it still does it. If it does, I'd turn off the juice and have a look at the switch and light fitting for loose connections etc.
 
one thing to watch out for, some people with a less than stellar knowledge of electrics wire other bits into light circuits. light circuits tend to be on 6 amp mcb, so if other devices are added to the circuit then it can cause tripping. otherwise youll have to do what you have been and just try and isolate what condition causes the trip to go.
 
Thanks.. There's been no changes to any electrics... Just started happening out of the blue this evening.
Just tripped again with only the stairs light on..
So not the landing light?
 
Flipped the braker for the lights back on, but in doing so it tripped braker No6, which doesnt seem to have anything attached to it, Or is that the RCD for breakers 8 thru 12?
so I flipped that back on too... ill try with the bathrom light being the only light on

:confused:

:confused:
 
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The photo's a bit fuzzy, but yes, it looks like an RCD. Given it tripped when you closed the lighting circuit MCB it's a fairly safe assumption that it covers that circuit, but I wouldn't want to assume whether it covers any other circuits too.

I should have said earlier, but don't do anything that you're not confident/competent to do - leave the circuit tripped and get a spark in if you're not certain. (It also avoids a load of 'can I have your stuff?' posts)
 
Hah... Yeah I'm just doing a process of elimination.
Tripped with only the bathroom light on...
Trips with only the kitchen light on...
I've noticed the electric ignition on my gas cooker is also on the same circuit... But I've not used the oven..
 
OK plot twist...
Went to bed to watch tv.. Reset breakers with no lights on... And it tripped some time later 'by itself'.. Both the light circuit breaker and the RCD.

So I just reset it again and it immediately tripped and a crack and a spark shot out of the bottom..

Now the RCD is flicking off and won't stay in the on position if the light switch breaker is enabled.

It's fine if I leave the light circuit breaker in the off position.

WTF...
 
I had very similar issues and it was a dodgy extractor fan. I have seen it be a leak from a shower as well getting into the light fittings below causing a ground fault.

But if you're not sure get a sparky in to check.
 
Thanks... Ive removed all the bulbs on the circuit and the fuse for the oven (it's a gas oven but has electronic ignition) which is on the same circuit.
Can't see any dodgy wiring anywhere or dampness.

The mcb is a 6amp BG cum B6.. Ive replaced mcb's in a previous house so I'm just wondering if it's worth swapping it out as I can pick one up in town for about £3 before I call a sparky?
 
I'd probably be calling a spark at this point. They will have the test kit to trace the fault and be 100% sure it was fixed. (I might be more cautious than I would have been because my parents had a major house fire which was attributed to an electrical fault.)
 
Yeah that's the next step it to get the wires tested by an electrician but that's gonna take time and cost a lot.
So I was thinking for the sake of £3...if it is a faulty mcb, unlikely but if the new one is tripping too then that's all I can confidently do really.
 
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mattyfez said:
Yeah that's the next step it to get the wires tested by an electrician but that's gonna take time and cost a lot.
So I was thinking for the sake of £3...if it is a faulty mcb, unlikely but if the new one is tripping too then that's all I can confidently do really.
Click to expand...
I would Change it.
 
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