A friend asked me to have a look at his kitchen light on Sunday. He turned it off, there was a pop, and the circuit breaker tripped.
He tried to reset the CB, but it wouldnt reset, just immediately tripped.
So, I go, thinking blown bulb or somesuch thing. The circuit covered most of downstairs, with all of those lights off obviously.
After checking numerous switches, disconnecting all the lights etc. I was no closer to finding a fault The living room had 3 switches with three lights connected to the 3 switches - all 3 way - lights on if one switch is flicked, off if another is flicked. The back of the switches were like a spaghetti farm.
I removed the switches in turn, to see if one was faulty. By chance, the first one was removed, and the CB could be turned on, with all lights working apart from the kitchen and living room. The switch was checked, and no leakage to earth, and switched fine on the meter. So now it seemed there was a fault somewhere in the wiring. I came to the conclusion that I couldnt fix it.
He then got a sparky in on Monday. He was there 4 hours. Apparently, one set of wires ran inside a metal sheath cover (the type you can use a nail to hold on). When originally fitted, one cable was too close to the nail, and had been compressed, so much so that the live wire had finally been pushed out of its insulation, 10 years after being fitted, and had touched earth, causing the CB trip.
He also could not understand why there were so many wires around, and had to call in his Son to help him find the fault.
So, the query is, if this ever happens again, how can you trace such a fault, without stripping out all the wires?
Ta Alan.