I've bought a metal (satin stainless finish, flush fitting) single light switch for my bedroom wall. I went to fit it today and discovered that it needs to be earthed to the metal box in the wall it will be fitted too. On looking into the wall box I note there isn't a terminal, but there is one or
2 holes that I guess I could drive a screw into; would this be suitable to run an earth wire from/to the light switch terminal? TIA matty
TonyB
really ? so any light fitting or switch that has an earth point needs wiring up? thats almost every fitting in my house. Meaning a re-wire of the whole lighting circuit. sheesh
Yes, unless the light fitting or switch is plastic or double insulated.
If your lighting circuit has no earth, you are restricted to plastic and double insulated light fittings and switches, until it's rewired.
Only 2, red and black
Guess it'll have to be a plastic one again then :o( thks matty
IMHO it should be earthed anyway. Presumably the two fixing screws are metal, and they (probably) go straight into a metal box....
Others may wish to comment...
as a favour I went to look at a neighbours wiring after they explained their
11 yr old son was getting a shock every time he switched on a particular light.Turned out the earth had been "taped back" and due to sloppy wiring the box and indeed the 2 screws were live.
Heaven help the lad if he had touched the radiator and turned on the switch at the same time!!!
A very common one I have seen is that a switch or socket has been taken clear of the wall for decorating and then put back. But dressing the stiff wires back into a small box is tricky and it is easy to end up with a wire "in the way" of a screw. As the screw is then screwed back in, it pushes the wire out of the way but cuts through the insulation and comes into contact with the copper in the process.
Not normally ever noticed, if the "box" isn't earthed and the switch or socket has a plastic front. Touching the recessed screw heads doesn't happen very often.
What can happen in an old, solid stone wall cottage (like we have many of around here) is that damp can get into the wall at certain times and the RCD trips..for no apparent reason..
The old sockets in my house were plastic, screws went into a wooden surround, like a box without a back. No metal box to conduct current from a stray wire. The above problem could still happen though.
Mind you, half the house was live when we bought it, the previous occupier had wired the immersion heater the wrong way and the plug melted before the fuse blew, the neutral was wired to the frame of the metal range and the whole range was live too. I got a leccy in PDQ who fitted an RCD and checked the rest. Even he missed the fabric covered wire to a lamp socket that had also been missed in the last rewire - that wire was nearly fifty years old!
TonyB
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