Earthing a chrome light switch

[cwhaley]

In the process of renovating the front room, we decided to ditch the plain white light switches with nice brushed chrome ones. I knew the house was re-wired in 2008 and that the switches all had earth cables in the back box.

The old switches are marked switch 1, switch 2 and COM. There is also an earthing wire which is screwed to the back box. The new switches are marked L1, L2 and COM with a point for earth.

My question is around how to connect the new switches up. I'm presuming the new wiring would be switch 1 to L1 and switch 2 to L2 with COM going to COM. The earth wire (currently screwed to back box) should then go to the earthing point on the new metal switch?

I've attached some pictures of the existing wiring and the rear of the new switch.

Can anybody out a dummy right on this one?

 

[JohnW2]

My question is around how to connect the new switches up. I'm presuming the new wiring would be switch 1 to L1 and switch 2 to L2 with COM going to COM.

That sounds right. If you find that the switch works 'upside down', swap the connections to L1 and L2.

The earth wire (currently screwed to back box) should then go to the earthing point on the new metal switch?

An earth wire needs to remain connected to the back box, so if you leave it as it is, you can take another bit of wire (with green/yellow sleeving) from that back box terminal to the earth terminal on the switch. Some would prefer to take the incoming earth to the switch, with a second bit of wire from there to the back box, but the current earth wire is probably not long enough to do that.

P.s. how did it get so messy in there?!

Kind Regards, John

 

[cwhaley]

Hi John - thanks for getting back so quickly. That makes perfect sense - I have a reel of earthing cable left to me by my dad so I'll run some of this from the back box to earth terminal on the new switch with the correct sleeving. That will then solve my earthing conundrum.

I have no idea how it got like that! I've only owned the house 7 months and the paperwork for the re-wire says it was done in 2008. You should see the filler that's been generously applied around all of the new sockets and switches!

 

[aptsys]

There's no need to have the earth connected to the pattress due to the fixed lug, so you could just take the earth to the switch plate. If it isn't long enough a flylead would work.

 

[ban-all-sheds]

An earth wire needs to remain connected to the back box

Why?

 

[JohnW2]

Why?

So that when some idiot undoes the faceplate screws whilst the circuit is still live and tugs the faceplate forward such as to yank the L cable out of its terminal, the box which the live loose end may come into contact is still earthed, hopefully leading to a protective device operating beore anyone touches the box.

One can argue that such is not a regulatory requirement, but I am personally not much happier (in someone else's house - I am not an idiot ) relying on faceplate screws to earth a back box than I would be to rely on faceplate screws to earth the faceplate.

In the OP's case, as I said to him, there is also probably a practical/pragmatic reason for installing a fly lead - in that I doubt whether the existing CPC is long enough for it to be comfortably 'transferred' to the faceplate - if that's what you would like him to do.

Kind Regards, John

 

[JohnW2]

There's no need to have the earth connected to the pattress due to the fixed lug, so you could just take the earth to the switch plate. If it isn't long enough a flylead would work.

As I've just written that may be true in terms of regs, but that 'fixed lug' ceases to be relevant (and ceases to be a method of earthing) once the screw has been removed. I therefore favour the cautious approach, particularly if I do not know "who might do what" with the accessory in the future

Kind Regards, John

 

[cwhaley]

I'm going to act on JohnW2's suggestion of running a new earth cable from the fixed lug on the back box to the faceplate. As I say I have plenty of earthing cable so it's not a problem to do. If I didn't do it, okay I will know it's not been done that way and would be sensitive when/if removing the faceplate. Future home owners though, may not be.

The existing earthing cable would probably reach to the faceplate, but there wouldn't be much 'flex' left.

Thanks.

 

[JohnW2]

I'm going to act on JohnW2's suggestion of running a new earth cable from the fixed lug on the back box to the faceplate. As I say I have plenty of earthing cable so it's not a problem to do. If I didn't do it, okay I will know it's not been done that way and would be sensitive when/if removing the faceplate. Future home owners though, may not be.

As I said, that's what I would do (for reason's I've given) - although, as you have seen, "opinions vary".

In case you did not realise, the "fixed lug" to which aptsys referred is one of the bits into which the faceplate screws are screwed. If at least one of these is 'fixed' (just a bent up bit of the box), rather than 'loose'/adjustable, then some people are happy to just earth the faceplate, hence relying on the screw into that fixed lug earthing the box.

Kind Regards, John

 

[ban-all-sheds]

So that when some idiot undoes the faceplate screws whilst the circuit is still live and tugs the faceplate forward such as to yank the L cable out of its terminal, the box which the live loose end may come into contact is still earthed, hopefully leading to a protective device operating beore anyone touches the box.

One can argue that such is not a regulatory requirement

One can, and this particular one will.

A back box is not an exposed conductive part. Earthing it in a more preferential manner than the faceplate of a metal switch is dangerous madness.

but I am personally not much happier (in someone else's house - I am not an idiot ) relying on faceplate screws to earth a back box

Please explain the circumstances in which you would come into contact with that box.

 

[JohnW2]

Please explain the circumstances in which you would come into contact with that box.

As I said, unless I take leave of my senses, I would not come into contact with a back box which had become live. However, I have explained the circumstances in which someone with less sense could (per what you have quoted).

I don't think I really need to apologise for personally adopting (and 'advocating') an approach which goes beyond the minimum safety standards required to satisfy the regulations.

Kind Regards, John

 

[cwhaley]

What I am going to do would be safe though, would it not?

The earth cable currently enters the back box and is connected directly to the box itself and nothing else, presumably because there is no need to earth the current plastic faceplate. What I will be doing is running a new earth cable from the new chrome faceplate to the earth terminal on the back box, which would then mean it is earthed more or less directly to the main protective circuit as well.

 

[JohnW2]

What I am going to do would be safe though, would it not?

Indeed so - as I said, it is precisely what I would do. If the existing earth wire were long enough to reach the faceplate comfortably, I might shift it to there and (again) run a new bit of wire from there to the back box - but, either way, I would have an explicit piece of wire connecting the faceplate to the back box - which I personally regard as 'safer'.....

What some people are saying that the regulations can be satisfied by just earthing the faceplate and relying on the faceplate screws to earth the box. Under most circumstances that is undoubtedly fine, but I personally would not do it. As I recently wrote, there is nothing wrong with exceeding the minimum safety standards required to satisfy the regulations.

Kind Regards, John

 

[ban-all-sheds]

There isn't, but that's not quite the same as saying an earth wire needs to remain connected to the back box..

 

[JohnW2]

There isn't, but that's not quite the same as saying an earth wire needs to remain connected to the back box..

It's not - maybe I should have included an "IMO".

Kind Regards, John