Earthing metal switches

Plastic switches don't need earthing apart from the metal fixing screws, just earth the back box and then you are OK.

Regs state that there must be a wired connection between back box and face plate even plastic ones to ensure that the exposed screw heads are earthed. Wether you connect the incoming CPC to the face plate or box is debatable, to the box is probably easier as you then only have one wire to the face plate.

The question was about the old metal ones @-)

Not quite. If there is one fixed screw lug on the back box, then there is no need for the fly lead. BS1363 is the relevant document.

So what reg is this and which plastic light switch face plates have an earth terminal?

I'd say so - in the same way as you'd run the earth to a socket terminal, not the back box.

Could it be the wiring pre-dated the metal plate switches? So whoever fitted them didn't add the earth wire?

I've certainly still got one switch with a metal part on my loft light. No earth since it pre-dates earths in lighting circuits.

If the backbox is metal, and it has at least one fixed lug, then it is in theory allowable to rely on the screws. If it has a proper earth terminal on the switch though, it would be good practice to run a fly lead to it from the box connection.

Also worth checking the switch itself - some are double insulated / Class II and hence do not require earthing.

heads

We are refering to metal face plates. B-)

I take it then that the wall boxes were not metal? Surely the screws earthed it. Brian

Now that is the logical answer.

:-)

Does BS1363 cover lightswitches?

no - that's BS 7671 (aka Wiring Regs)

They were metal, but I thought it would be safer not to rely on just the screws.

The switch in my loft is all metal MK about 40 years old, but it is earthed.

I'd not either since I've seen some pretty corroded ones on older installations. I'd add a wire link between the two - as I also do with sockets.

"charles" wrote

My whole house had those orrible tacky brass metal light switches, as well as brass plated light fittings in every room except the shower room, where there was one of those evil looking UFO heater lights, positioned nicely so it could almost warm you up whilst in the shower, as it partly overhung the top of the cubicle!!!

And of course i found out the entire lighting circuit (only one for the whole dormer bungalow) was wired in that early '70's 0.75mm wire with no earth, even the heater light in the shower room was on non earthed .75mm cable.

When i replaced the floor upstairs (standard 12mm chipboard!!! it was crumbling and my foot had gone through it in a few places) i found the earth wires for the sockets all went around the junction boxes and were twisted together, it was machine twisted by the looks, a practice i thought died out before the war.

I have seen places wired in the late 50s with a similar arrangement - rubber insulated twin, and separate multi strand galvanised steel earth.