Locating a short in home lighting circuit...

[AL_n]

Can anyone give me any tips on how to locate a short in my house lighting circuit?

I was sitting here at my desk and the whole upstairs lighting went out. The circuit breaker had flipped. When I tried to un-flip it, I saw a spark and it wouldn't flip back, so I conclude the short is still present.

No alterations have been made to the wiring for several weeks here, so I can't imagine what might have happened. I don't have rats in the loft.

I have a mains testing screwdriver at hand (and a multi-meter if needed).

Thank you!

Al

[Clive George]

Are all the lights switched off? Yes, I know it's trickier to tell if there's no power, but if you do manage to switch one off and have the power come on, you've got a really good clue where the problem is.

Then start at the bulbs - remove, does everything else start working?

IME you don't need to do much more to find the problem. It'll probably be a bulb or switch. Of course having said this you'll now be the one with the short hidden in the plaster.

(is that a neon screwdriver? :-) Regardless of the comments flying around this NG (which are probably worth reading), it won't help you, because you can't turn the power on yet)

[Andy Burns]

Try turning all lights off (or reversing them if they're 2-way or 3-way) and resetting the breaker, turn lights back one-by-one until it trips again, might narrow it down, unless the problem is isn't in a switched part of the circuit.

[John Rumm]

I was about to say he could turn screws with it, but then again they are often too small to do that well ;-)

[John Rumm]

Given the circumstance, a lamp failed short would seem most likely. Turn off / remove bulbs to try to find it.

[AL_n]

Andy Burns wrote in news: [e-mail]:

Thanks to you all, for the helpful suggestions. This is strange: I switched all the lighs off and then flipped the circuit breaker. It flipped back to the "on" position.

I then turned all the lights on, one by one, expecting one of them to cause the short again. None of them did! Now all the lights are working.

What does this mean? It makes no sense to me!

Al

[NT]

[e-mail]:

sometimes filament lamps arc over when they fail, causing a very large current surge.

[Graham.]

They are great at unscrewing things, screwing them up again usually results in the red cap unscrewing itself and releasing the pingfuckits.

[AL_n]

NT wrote in news:11eef274-6467-42dd-8475- [e-mail]:

I only have one incandescent bulb on the affected floor. It is a 150W bulb. However, it has not blown. All the other bulbs are fluorescent or LED.

Al

[ARWadsworth]

How long is a piece of string?

Maybe the MCB is "tired" and will not switch on when under load? It is not uncommon.

[AL_n]

"ARWadsworth" wrote in news:jjr1ta$9cs$ [e-mail]:

That seems like a plausible explanation. I wasn't aware of that phenomenon.

Hopefully all will be well from now on! BTW, my circuit breakers are plugged into an old-style fuse box. It's not one of the more recent consumer units that flips their MCB's every time someone breathes too heavily.

Al

[ARWadsworth]

IMHO the type of MCBs you have (plug in Wlylex fuse replacements?) are the sort of MCBs that often fail to turn on when under load.

[NT]

dont-email.me:

The reason they often flick off when turned on is that many appliances and lamp types draw a surge of current at switch on.

NT

[Brian Gaff]

Something only shorts when it gets hot? Brian

[Brian Gaff]

But he said they all work, and in any case normally this failure tends to vaporise the shorted area and the bulb is then just open circuit. I suspect something getting hot or failing intermittently. It could be a leaky capacitor that eventually breaks down but recovers enough to allow the reconnection. Some older Thorne fittings seemed to have an annoying tendency to do this sort of thing. Brian

[Brian Gaff]

Might be worth turning all off and watching if the meter runs faster when you connect the circuit, and then doing the same with each individual light and see if the current increases. Ideally you would need some kind of clamp meter to be sure what is going on if you suspect one fitting or part of the wiring. Its a real pain when things are not constant. Brian