MCB Tripping On Lighting Circuit - Out Of The Blue?

[TMess]

Firstly, no alterations to any lighting circuits have been undertaken in years. Nevertheless, yesterday, the MCB on our Consumer Unit for our upstairs lighting circuit tripped. I switched it back on and a couple of seconds later, it tripped again, we once again I flicked it on and it stayed on all night. This morning, it tripped once again, and then again after I turned it back on.

Before calling out a real sparky, is there anything obvious I can check that could be causing this (light bulbs, 12v transformers, etc.)?

 

[SYKRAPS]

It could be a 12v transformer touching a 12v lamp in the attic, this is fairly easy to check and can be caused by things being thrown into the false roof void.

 

[TMess]

Did the electrician narrow the fault area down for you just out of interest?

Nope. He only removed one room out of the equation as it's the only room which had a pendant light and all the connections were made in the ceiling rose. He couldn't check the rest of the rooms as it turns out we have junction boxes all over the place underneath the loft flooring. It was getting late and dark and neither did I want to pay for his time to lift boards up, and I'm sure he wasn't fussed on the idea of doing it anyway. I said I would call him back once the boards are lifted and if I don't find the fault myself by then.

Hence, I got lucky by finding one junction box after only lifting three boards and it turned out the faulty cable was within it.

 

[TMess]

Get some cotton thread and a hair dryer, blow the thread up or down the chase untill it comes out the other end.
Tie on some string, pull through, then a single conductor then some T&E.
Will be easier with someone to help guide in.

That's a great shout. Will give that a try. However I have my doubts that the thread will probably just get stuck in brickwork joints.

 

[SPARTYKUS]

Put the hairdryer on "turbo" :gunsmilie:

 

[TMess]

Didn't work unfortunately, even tried sucking with a vacuum at the other end. Some grit must have fallen as we removed the old cable and even a piece of clothes hanger wire won't get through. It will have to be tile off time. Thanks for all of the help fellas.