Light circuit keeps popping fuses.

[alamb]

Hello folks,

I seem to be having difficulty sourcing the fault, in my downstairs lighting that keeps popping fuses.

I have two lighting circuits in my home, one for downstairs (and the top hall light) and one for upstairs.

The downstairs circuit has 9 lights, all with 11W 96mA bulbs inside the fittings. The problem is that I cannot find what keeps blowing the fuse. I have opened up all the switches and the fittings thoroughly checking for any frayed or loose cables but all are fine.

The fuse itself is a 5 amp, and I have put about 6 fuses in try different combinations of lights but what happens is they all come on fine for a about 4-5mins and then the fuse pops. I tried a 10Amp in the fuse box as well but that popped after around 10 mins.

To try and figure out which light (or switch is the problem) I have out a 3Amp in the fuse box, hoping that it would pop as soon as I turned a single light on (as it should take less to blow the 3Amp) but that also lasts for about 4-5 mins before popping (with all lights on).

I'm quite bewildered as I'm not too bad with electrics.

I should also mention that this just started happening all of a sudden last night; it’s never done it before.

Any responses would be much appreciated.

Adden

 

[ban-all-sheds]

I wonder if using 110V bulbs has anything to do with it...

 

[alamb]

These are 230-240V bulbs.....(energy savers)

N2UL11B22 bought from B&Q

 

[canduit]

1. Do you have any dimmers on the downstairs circuit? 2. Remove the bulbs, does the fuse still blow? 3. Does the fuse blow when the switches are in the off position?

 

[ColJack]

1. you have water in an outside light and no RCD..
2. you have rodent damage to the cables somewhere either under the floors or in the loft.

number 1 causes current to flow from L-N ( or even to earth ) via the water.
number 2 cause is the rodent still attached to the wires, albeit rather crispy and carbonised now.

you need a sparky in to check the IR on the lighting circuit in question

 

[disinfo]

I wonder if using 110V bulbs has anything to do with it...

OT (Sorry OP) but we received a variation order from BAE systems recently, we are no longer allowed to use 110v lighting on any machinery that we supply.

The reason being that someone in their H&S department is worried about employees stealing the bulbs and them exploding when they put them in their fittings at home.

You'd think a weapons manufacturer would be more worried about other things going missing.... i.e. weapons

 

[alamb]

No dimmer switches anywhere in the house, and the fuse does not (has not yet) blown with the bulbs out, and its has not with the switches in the off position.

Ill keep it like this for antoher 30mins just to make sure it does not blow.

Coljack - There is only one outside light, that has no water in it, I checked when I removed all the fittings earlier. Plus its not rainned in a few days, and no water leaking from anywhere.

I'm also pretty sure there is no rodent damage, I was up the loft today, checking it all out, and I'm pretty positive there is no rodents. There certainly no cable damage up there. However under the floor boards could be a different matter. (Though there is no other signs of rodents)

Canduit, I'll do more troubleshooting, to make sure that the fuse doesnt blow when the bulbs are out or when the switches are open.

I've just finished my HND Electrical Engineering, and this is still quite a puzzle.

Thanks for the help so far.

Hope I get this sorted soonish, Starting to run out of fuses

 

[ColJack]

if you've just done your HND the presumably you'll have a multimeter..
a good start would be to disconnect the wires from the DB, remove all lamps and measure the rough resistance between the L-N-E..

if you don't have any dimmers or transformers, then it should be fairly high.. in the megohms range for a regular multi meter. ( for an empty circuit with no electronics on it, the meter should read it as open circuit between L-N-E.. )

 

[alamb]

Right, I have ruled out the outside light and the livingroom light.

I took the multimeter to circuit and the fuse box it seems alright.....Im starting to think that it might be a problem in the kitchen. Now in the kitchen There is 2 lights controled by a 2 Gang switch.

On the other side of the kitchen there is a 3 gang switch, this controls the same two lights as the two gang in addition to another light just above the backdoor in the kitchen (Inside).

When I was in the kitchen, just before I wrote this, I was testing when I heard a pop, as I unscrewed one of the light fittings (the switch controlling the light was on, and there was no bulb in any of the kitchen lights. There was no spark and It was hard to identify from where the pop came from. It wasn't the fuse popping (As when I put the bulb back into the fitting it came on).

Last night when this first happened, I heard multiple pops, before the fuse blew.

Checking the fittings this morning all wires a securely in place, and there is no scortch marks on any of the cableing.

Any ideas as to what may be happening here.

Maybe time to call in a pro?

 

[alamb]

Update: Its definatly the 3 gang switch. Pushed the middle switch on and there was a dull pop (fuse still fine), and the light came on.

Still don't know the cause as the wires inside the switch are fine.

 

[alamb]

Problem Fixed.

Lifted the floor board in the bathroom. Theres a radiator in there, that been ever so slightly leaking, its dripped onto the cable that runs down to the 3 gand switch, and the copper pipe (thank christ its earthed) that carries the water has been touching the cable.

I've moved the cables further along a re-insulated them. Thanks for you're suggestions. Been ever so helpful.

 

[Adam_151]

Glad to see you have fixed the fault. you mention fitting 3A and 10A fuses to the lighting circuit... therefore I am guessing the fuse in question is a cartridge fuse and you have been using ordinary plugtop fuses?

I know the size of a 5A BS1361 (which are cartridge fuses for fuseboards) is very similar to the size of a BS1362 fuse (cartridge fuses for plugtops), but the size is not identical and also there are differences in breaking capacity and fusing capacity, so a 5A plugtop fuse is not a suitable replacement for a 5A 1361 even if it looks like it should be!... so just make sure noe the issue is solved that you end up with a 5A 1361 in there

 

[alamb]

Thats originally what I had in the board, but went through all of my spares the last two days and as its sunday, I'm unlikely to be able to get new fuses, but first thing in the morning, Ill go down to the local electrical shop. I'm going to see a mate of mine about getting Trips fitted instead, less hassle.

I hope one night doesn't make too much difference.

Cheers again

 

[Adam_151]

I hope one night doesn't make too much difference.

It'll be fine for the short term, yes, just thought I'd point it out as many people are unaware that they are different

I'm going to see a mate of mine about getting Trips fitted instead, less hassle.

I wouldn't bother unless you are going for a fuseboard change to one with RCD protection, replacing certridge fuses with MCBs id probably a waste of money as they dont offer any more protection[/code]