Lighting Fault - Earth S/c to Phase

[DanielR123]

Hi,

My light MCB has tripped and won't go back. I've disconnected the wired from CU, and tested for continuity and found that the Earth is S/C to phase. What exactly does this mean? Where is a likely cause of the fault?

Cheers

Daniel

 

[JohnD]

Nail through a cable very likely.

Might be rodents eating the insulation, might be water in a fitting, might be incorrect wiring if someone has recently changed a switch or rose, might be a wire come loose for no apparent reason and touching a back box or a terminal. It will not take you long to take all the light switches off and look behind for a loose wire.

If you have recently fitted or altered something then check that first.

As lighting circuits are wired radially, if you disconnect a ceiling rose in about the middle of the circuit and test again, you will see which half has the fault. then you can halve it again and again until you narow it down to a section of cable or a fitting.

 

[DanielR123]

the lights are really badly wired, the switches are being used I think to supply the next light etc, like the cieling rose should. I started upstairs and took all the switches off and disconnected all the wires. This got rid of the fault at the consumer unit and some of the switches still had the fault. I tried to see if the I turned the MCB on, whether it would trip, it didnt, but no lights came on though, Am i right in presuming that I've probably removed supply to the first light? Anyway im going to try connecting each switch individually to see when the fault reappears, when it does, what next? Any suggestions would be grand, i'll probably get an electrian to rectify the fault when i find the dodgy wire, i just want to fnd the fault to save his time.

 

[breezer]

you have answered your own question.

when you find it you just change the affected part / cable, so if it is a nail / damaged cable change cable job done

 

[Steve]

the lights are really badly wired, the switches are being used I think to supply the next light etc, like the cieling rose should.

Nothing wrong with that. This is becoming more popular as traditional ceiling rose fittings are becoming less popular. Saves using un-accessible junction boxes