Fuse blowing on reconnecting earth in lighting circuit

Hi all,

Have recently bought house and refurbished before moving in. I have now replaced all light fittings which was pretty simple but have a problem to do with earth connections. To give you an idea what i'm on about - the light circuit in question connects from hallway -> Bedroom 1 -> Bathroom -> Bedroom 2 -> Bedroom 3 where it terminates.

Now during the renovation the bathroom fitter fiddled with the bathroom lights so he could plaster the ceiling, for some reason he also seems to have fiddled with the old light in Bedroom 1 and left the earth wire out (the one going to the bathroom) thus leaving light fittings from bathroom onwards without earth. The reason he did this was because when I reconnect it it blows the RCD, if left unconnected the lights all work. I am unsure how it was prior as i hadn't had a look before replacing the light fittings after he fiddled with them.

Now i realise this could be classed as a pretty bad problem but i need some pointers on where to look, am i right thinking that something is causing earth leakage and i just need to check every switch/light for L or N touching the earth wire?

There are no metal fittings so i don't believe there should be any real risk however i want to get it right without calling in a sparky to what i think is probably a 10 minute job.

Thanks

Sounds like the bathroom fitter may have ballsed something up although this fault could have been there previous, did you have a periodic inspection report carried out on the wiring before or when you baught the property??

I would start by opening every ceiling rose, junction box and switch and looking for obvious signs of a short and checking the cables for damage where they are exposed and visible. Best area to begin would be the wiring for the bathroom lights.

If that doesn't show any signs of anything major then you are going to need an insulation resistance tester and take the installation apart to test which cable is damaged.

DONT work on live electric!!

Although you say everything is plastic it doesnt mean that no earth is required, if you have metal boxes in the walls for the switch then there need to be earthed.

he probably re-fixed a board up and put the screw through the cable..

Unfortunately i didn't have a report done as time got in the way, although i had planned too originally. I will check all the fittings and switches as a number of others were also detached and then reattached whilst walls were skimmed etc

Will also check in loft for screws through wires, good tip

thanks to both of you and for safety message though i would never work on live system, it would terrify me!

if switches have been off then it is possible that a wire has become trapped. Not doing the PIR before hand could prove quite costly and mean that your new plaster needs hacking into. It is VERY important that the earth remains continuos throughout the circuit and that there is a connected earth at each accessory.