I wish to replace my plastic light switches with metal ones, but there is no earth wire from the supply. I have been told that it is possible to earth the metal switch by running a wire from the metal switch to the wall mounting box. Would this be safe in the event of a fault?
Thanks.
No, it would be exceptionally dangerous. If you don't have earthing from the supply, then you'll have to either use plastic switches or rewire the circuit.
Christian.
In the case of plastic switches presumably one would have to also use plastic screws also?
Yes. Although the practical solution is to replace the box with a plastic one (which then allows metal screws). Metal screws in an unearthed metal box aren't kosher (although commonplace).
Are metal light switches no more dangerous than metal screws in plastic light switches, then? I suppose what I'm trying to find out is how much of a risk this really is ...
They're about the same, as a risk of going live from a loose wire, but obviously the risk of finger contact is much higher.
Yes. You are exceptionally likely to touch the metal surface of a light switch when using it, whilst you are very unlikely to touch the metal screws. When you do so, you'll have a poor connection with them and are more likely to break contact quickly during the resulting spasm.
Christian.
Can you actually *buy* the necessary plastic screws for this purpose?! (not that I need or want any)
David
Plus it's presumably more likely for a stray wire in the socket box to come into contact with the relatively large area of the back of the faceplate than the shank of a couple of screws passing through.
To the OP - the topic of unearthed light switches comes up here quite often, and quite often it emerges that the questioner *does* actually have the missing earth wire present, it's just been cut back or bent back out of the way be someone previously who thought they didn't need it or it wouldn't matter. Have a good look. It is likely to be quite an old installation for the earth wire to be definitely absent.
David
Yes, but you won't find many who would bother. They're not exactly easy to find.
Christian.
Also, PVC wiring without earths was only installed over a relatively short period (well a decade or two, anyway). You should check to ensure that the wiring isn't old rubber stuff, which will probably now be in a dangerous condition. If it is PVC, then it should be safe enough, provided plastic fittings are used.
Christian.
Good point - if it's crumbly old rubber, you shouldn't even be
*thinking* about mucking about with changing the faceplates anyway...!
I remember seeing some metal-faced light switches where the packaging stated that they were double-insulated. Presumably they'd be suitable for non-earthed systems? I'm not sure where - probably CEF or similar. Are they common?
I've noticed one or two switchplates with plastic caps to fit in the screw holes
I just don't believe they can be, unless they have an integral strain relief for the cable, not merely the individual cores.
Thanks very much for all your advice, guys. Much appreciated. I'll definitely have a root around in there to see if the earth wire is out of sight somewhere. There are obviously earth wires coming out of the supply that feeds the sockets, so I guess they're in there somewhere :-)
possible
no its not
no
plastic
if all your wires are fixed securely, no stragglers, no choc blocks, you check the wire isnt cut where it goes through the hole in the backbox, and if your wiring is arranged so that nothing will move the wirs at all, the risk would be very small - but not zero.
I dont recommend doing it, though I'm sure there are much bigger issues in most peoples lives than how many unearthed metal switches they have.
To get it in perspective:
a) there are lots of products on the shelves built to exactly this standard, and no-ones doing anything about them. Probably 50% of us already have such kit at home and arent worried about it. b) crossing the road is a bigger risk. c) its about as safe as American wiring, maybe better d) its your family that will be using it day in day out, I wouldnt want that on my mind. e) does it really matter whether the switch is plastic or metal? f) while the odds of it going wrong are minimal, do you really want to expose your own kids to a remote possibility of death for no sensible reason?
NT
In message , Sootbeast writes
Not necessarily - it was common/normal in the 1960/70's (not sure when the requirement for earthing came in) to use cable with no earth on the lighting circuits, though an earth was used on the sockets circuits.
All the 'newer' (as opposed to the ones that still had the '30's rubber wiring) lighting circuits here were like that.
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