MCB Fault Location

[mayniak08]

The MCB on my upstairs lighting trips and wont reset.

I have removed all light bulbs ( not sure why ? ) , and also checked the wiring at every switch and every ceiling rose ,but the MCB still trips.

I then one-by-one disconnected a wire from every switch - hoping that this would isolate the wiring in that particular room , and therefore at least highlight which room was causing the problem. This still didn\\\'t help. Should I have disconnected every switch all together , and then one-by-one reconnected and tested the MCB ?

Also I read in one of your posts that the main circuit breaker switch should be turned off before restting the MCB. I haven\\\'t been doing that and have been getting a \\\'flash\\\' when resetting the MCB. Am I doing something very dangerous ?

Finally , is there a standard search procedure to locate the faulty wiring causing the MCB to trip ?

Any help would be appreciated - the candles are nice but ..

[ban-all-sheds]

mayniak08 wrote:

The MCB on my upstairs lighting trips and wont reset. I have removed all light bulbs ( not sure why ? ) , and also checked the wiring at every switch and every ceiling rose ,but the MCB still trips.

Have you recently done any work involving drilling, screwing or nailing into floors, walls or ceilings?

Quote:

I then one-by-one disconnected a wire from every switch - hoping that this would isolate the wiring in that particular room , and therefore at least highlight which room was causing the problem. This still didn\\\'t help.

It won't, and if you look at diagrams of lighting circuits you'll see why.

Quote:

Should I have disconnected every switch all together , and then one-by-one reconnected and tested the MCB ?

That would also do no good - you need to start breaking the lighting circuit into segments at the ceiling roses/JBs/fittings, not at the switches. If you look at diagrams of lighting circuits you'll see why.

Quote:

Also I read in one of your posts that the main circuit breaker switch should be turned off before restting the MCB. I haven\\\'t been doing that and have been getting a \\\'flash\\\' when resetting the MCB. Am I doing something very dangerous ?

Well - not safe, and not doing the MCB any good.

Quote:

Finally , is there a standard search procedure to locate the faulty wiring causing the MCB to trip ?

I fear that your lack of understanding of how lighting circuits are wired means that you can't do this yourself.

I'm not being unhelpful - if you can't work out what to do from the circuit diagrams you have no chance of doing it safely or successfully. And do you have any test equipment?

Quote:

Any help would be appreciated - the candles are nice but ..

Time to call an electrician. If from my first Q you can identify where a cable might have been damaged it could shorten his search.

__________________
I mustn't warn people that the "experts" on the plumbing forum can't be trusted to tell the truth.

[mayniak08]

Thanks for the prompt reply .

That is actually very helpful ; knowing what you don't no is always worth knowing ! .

I guess my school-boy concept of light bulbs in parallel with switches on each one was a little too naive.

Your right , time for someone time served.