New Light fittings tripping Consumer Unit.

Hello,
I recently replaced two very old wall lights and ceiling light, and the 2 gang light switch to modern chrome fittings, in my bedroom.

This was straight forward, having noted where the wires went before hand and connecting up exactly the same way.

Both ceiling lights and wall lights seem to work fine. But after leaving both sets of lights on for a while (about an hour), my consumer unit tripped. This has happened a few times. The first few time, just the light circuit tripped, and could be re-set after a while. The second time the whole consumer unit tripped. After trying to re-set the consumer unit, the separate trip switch kept tripping, so all power to the house was off.
I checked the wiring whenever this has happened and everything is tightly connected. The latest problem was cured after taking one of the lights off the wall to check the wiring (which was fine), then replacing, the consumer unit on the wall. The consumer unit stopped tripping.

I'm wondering if it only came back on because : The consumer Unit / The Fittings/ Or the cables had cooled down after over heating?
Or had I released a short or a trapped cable (unlikely as I've been extra careful to tuck the wiring into the fittings as instructed.)

I was wondering if the light was faulty and was overheating, as the lights, even now, still work, I'm too afraid to leave them on too long again incase the same thing happens again.

The bulbs in the new lights are of the halogen (tube) variety, so I'm wondering if the wiring / Unit, can't take the wattage required by these lamps, compared to the previous light bulb lights. (Note: Other lights in the house were switched off when the above trips occured)

I'm relunctant to get an electrician in, as like I've said, you can fiddle around with the lights, and the lights work, and you think the problem is solved, just for the unit to trip again a few weeks later. Would an electrician be able to diagnose the problem if the unit doesn't trip when he's there? Don't want him to have a fiddle, say there, everything fixed, take £££'s off me, just for the thing to trip again a few weeks later.

Any advice greatfully received.

You could have trapped a wire behind any of the lights. Or did you have to drill any new fixings for the wall lights ?

The behaviour you describe could be caused by a cable or joint somewhere overheating and by softening/melting insulation gradually/intermittently creating first a L-N fault, which tripped the MCB, then a L or N to E fault which tripped the RCD.

No signs of overheating when you took the light off the wall?

Or it could all be going on inside the light itself - you're not using the wrong wattage lamps?

Hi Both, thanks for your replies.

As to catching wires behind the fittings, I've checked and double checked this and all seems fine, although it does seem strange that taking the lamp off the wall and re-connected it sorted the problem last time. Perhaps I could dig/chase out a bigger hole behind the fitting to give the wires more room. I did have to drill the new fittings, alothough I'm very confident that these holes are far enough away (either side) from the route of the wire, and I haven't nipped them.

There were no signs of over heating from the light fitting other than a very hot light and fitting, but I gather its quite normal for them to get very hot. No scorche marks or signs / smells of burning etc.

I'm using the lamps supplied with the light, so that shouldn't be a problem, but it is possible that the wiring or fuse or something isn't up to the increased load of this halogen (instead of traditional light bulb) fitting?
Can you get energy saving halogen type bulbs and would these reduce the load on the consumer unit?

One question, I don't mind getting a sparky in if I know he'll find the problem and fix it, is it likely he'll be able to find the problem though with the 'time delay' in the tripping of the box. Everytime I've fiddled with it, I think I've fixed it, only for the box to trip several days later, when using the light.

I'm starting to wonder if the lights are faulty, and whether I should just buy two cheap wall lights and replace with these to see what happens.
Misses won't be happy with cheap fittings though after having done the bedroom out!

Have you added up the wattage of all the lights on the circuit to make sure you aren't simply overloading it?

That would be my guess too.

Clue 1:

But after leaving both sets of lights on for a while (about an hour), my consumer unit tripped.

Clue 2:

The bulbs in the new lights are of the halogen (tube) variety.

Yeah, but...

Cyril2 said:

Note: Other lights in the house were switched off when the above trips occured)

Click to expand...

So unless these wall lights are getting on for 1kW each....

And why would the RCD trip?

I have a sneaky feeling that there may be a junction box somewhere that is getting overheated, prob due to a poor connection.

Thanks Gents.


I'll trace back to the junction box, which unfortunately is in the attic and I suspect, buried under floor boards!

Anyone know if you can get energy saving bulbs that are the same shape as the halogen tubes? Might reduce the loading abit?

Thanks