The back box seems to be live on my light switch.

[martybli]

Just changed a 2 way light switch and screwed it on. Put my electric screw driver on the screws after and it lit up. I went upstairs and tried the other switch and that is the same. The only other thing I did was put a junction box in when I replaced the ceiling rose.

Could I have made a major error? Where do I start? Hope someone can help as I have no lights now as I have kids in the house and have pulled the fuse.

Cheers Martin

 

[Adam_151]

Have you ever received a shock from the screws? if not then chances are its not 'really' live, but stray capacatance causing ~120VAC to appear on the (unconnected) CPC (earth) . If this is the case, you need to track down and repair the lack of earth continutity on the circuit (open fittings that have been looped into and check that the cpc has been terminated correctly for a start*)

*mate of mine lives in a new build house had this problem, it was theorised that the cpc slipped out as the fittings were screwed back, I'd have liked to have seen the EIC for that house :

 

[martybli]

Ok thanks Adam. How do I test if it is live? I could do with my lights back on?

 

[martybli]

Just about to go in my loft and open junction boxes etc to make sure all the earth connections are correct. Is it worth me going to B&Q to buy any sort of testing equipment that would help me? If so what would I need to get?

Regards Martin

 

[Adam_151]

A multimeter and a wander lead (20m of green/yellow of any sensible size would be ideal) and probably a plug (probably easiest way to connect to earth, unless you feel competant to lob it onto the earth bar in the CU)

So you can work along the lighting circuit testing continutity to earth as you go, using continutity setting on your multimeter

 

[martybli]

Thanks Adam.

Do I take it the wander lead is something I make up myself with the 20m of Green/Yellow cable and the plug? Do you connect the cable to the earth point on the plug then plug it in? With the multimeter do I just touch all the earth wires in junction boxes, ceiling roses, switches etc until I find the problem. (Whilst this is happening is the multimeter connected to my earthed wander lead?)

Sorry to be thick but I don't normally do this sort of thing.