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Harringay, Haringey - So Good they Spelt it Twice!

Electrics / wiring help needed - what does this wire do in wall mounted switch

I detached some switch and plug socket faces from their recessed boxes to do some decorating.

With decorating nearly done, I've come to screw a wall mounted isolating switch back on to its box and seen there's a bare wire that is not attached to anything.

Please see pics.

There's no obvious connector for it to go in to. There is an earth connector in the recessed box but that's on the other side to the wire.

The switch still works.

Any thoughts on what it's for or how to find out?

Thanks

Tags for Forum Posts: electrics, wiring

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Hi, 

Just to state upfront, I'm not an electrician but my father was, so I spent a fair portion of my childhood around stuff like this... 

Bare copper wires like that are earth wires, which you can and should sheath with a yellow/green sheath. So it could be a second earth and supposed to be in the earth connection the yellow wire is in.

It's a mix of new and old wiring as you have brown and red live wires.

The yellow wire is unusual and old colouring and could be a live wire (see: https://www.quora.com/What-is-the-British-color-code-for-lighting-w...). If that's the case, it shouldn't be in the earth connection. 

I'd get that checked by an electrician. You don't want your house burning down.

Thanks for the reply - electrician sounds like safest option.

As Leanne has said the bare wire is normally the earth cable and indeed someone MAY have used the yellow as a second earth (Perhaps because the bare wire is a bit short), confusing the old and new colour systems. But that is the thing... MAY. You should get an electrician to check which is has been connected to check that the earth has been correctly connected at the applicance end and sheaf the cables with the correct modern colour codes. 

I also notice the diameter of the cable is smaller in the 3 core cable, not a problem so long as the fused switch has a 3 amp fuse in it.

My complete guess here this is the switch to your boiler, however it used to be the thermostate (hence the 3 wires,2 for power 1 for switching) and when the boiler was replaced a wireless thermostate/ or the themostate was just moved so now only 2 wires are required who did it use the "spare" yellow for then earth.

Agree yep a sparky is the way to go!

The switch is actually for a bathroom mirror - with the switch in the next room.

Electricians were in a few years ago to rewire the socket circuits.

Thanks for your reply.

Does it look like it's part of the same cable as the wires next to it? If so, it's probably the fourth wire in a four-core cable. Google will tell you more about it. I've no idea if the wire had been attached to the socket. It looks like it's been cut shorter than the others. I wonder if that indicates that it was cut back as redundant. Equally, it may just have been cut inadvertently short. I've changed sockets like this before, but only after photographing the original set-up and following it religiously. If I were you, I'd ensure I had a expert opinion before proceeding. 

Taking pics - top tip.

Here I didn't detach the wires, I just turned circuit off and gently eased the face away from the box. Weird that I didn't clock the wire then.

I might have knocked it during decorating and that did something.

Anyhows, defo getting someone in to look at it.

Thanks v much!

It must be an earth connection, like the yellow wire on the right and the bare wire (with a just-visible yellow-green sheath) on the left-hand side. It presumably was stuffed in the same hole as the yellow wire on the right. The L and N connections are clearly labelled. Are these connections labelled 'E'?

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