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?
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
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!
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