The clue may be in your thread title ie has it been raining recently? In any case the first thing to suspect is any outside lighting.
Also sometimes there can be unexpected things wired to the lighting circuit, my gas central heating was like that for years.
With the nice weather today, I could finally got round to sorting out some small leaks in the joints of the conservatory gutters. It took a couple of hours but hopefully they will be ok. After finishing we decided to relax and have a look round the garden to see what was in leaf and bloom. It didn't take long and we came back in, and my wife started to put the flowers our daughter had bought for Mothering Sunday in a vase. It was then I noticed the torch emergency light was on, indicating there was a power cut...
One of the RCDs in the consumer unit had tripped. I turned off all the MCBs on that side, and switched the RCD back on. Thankfully it stayed on. Turning on each of the MCBs in turn revealed it was the house lights circuit which had tripped it. All the lights were off at the time, and I don't know why they tripped the RCD (which still trips when I turn the MCB for the lights back on).
Bugger! The cabling here for the lighting is not good (see my posts early last year about my lounge wall lights saga...), and some is earthed and some not. I doubt this one is going to be an easy fix. An "Adam" might be required.
LOL! Just a bit like everyone one else for umpteen weeks, but strangely not in the past few days. No problems while it was tipping it down (although the chimney needs repointing as some water was getting in), but it waits till it was sunny and dry.
Nothing would surprise me. The wiring here leaves a /lot/ to be desired...
While there could be a number of possible causes, including an insulation resistance problem (including cable damage), moisture ingress, or it could be a earth / neutral short on the circuit.
You could try a "binary chop" to try and narrow down the fault location. So isolate the circuit and pick a lighting point you can get to, which you estimate is about half way along the circuit. Open its ceiling rose (power off obvs!) and disconnect the feed out to the next lamp. Then power back on and see if it trips. Either way you have hopefully now eliminated one half or the other. Reconnect, and then repeat the split half way along the remaining half.
That's a sensible approach. I'll have a look in the loft and see where the cables go. Of course, the lights in the loft are run off the lighting circuit so I'll have to get some other lighting up there.
I'll still try that to see if I can find the fault, but I'm probably going to go for a partial lighting rewire anyway. Why?...
The split CU has an MCB on each side to do with lighting. One is marked "Lights house", and it's that side which has the fault and trips the RCD. The other side is marked "Lights kitchen", and is fine - except it's not..
We think the kitchen was redesigned 15 - 20 years ago, and the opportunity was taken to rewire the lights (hence the MCB). But whoever did it didn't rewire the underunit fluorescents, as they are still connected to the other "Lights house" MCB! But it gets better - we believe that at the same time as the kitchen was done an en-suite was added to the master bedroom. And - you guessed it - the en-suite lights are run from the "Lights kitchen" MCB! We found our last night the en-suite lights were working while the rest of the house lights were off.
I am probably capable of doing the rewiring, but I'm getting a bit long in the tooth to crawl around the loft, and with all the dust and rockwool up there I'd rather save my P3 mask for more important things.
So with them all off it trips. Could any of the wiring be anywhere near the work you did earlier. It would seem a tremendous coincidence if it was just a random fault. I guess one could just short the whole thing out with only a fuse protection and looked for smoke listen for the bang etc!
Brian
What?! You doubt my wiring ability?! :-)
But, as so often with these things, it's only there to drive you mad. I thought it would be worth turning on the MCB this morning to see what happened. Well, of course, the RCD did not trip! The lighting circuit is apparently working without problem.
I now wonder that, if I opened one of the switch or junction boxes, I'd find a partially cremated insect which is no longer shorting to earth.
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