Light switch earthing question

Pulsedriver

Pulsedriver

Pulsedriver

Soldato
Joined
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UK
Hey folks,

When I moved in to our house just over a year ago I started to change the light switches from the white plastic type, to the chrome / metal style ones with plastic switches.
At the time, I realised I needed to add an earth to them, as the plastic ones did not need them but metal ones would etc.

Anyhow, with some of them, this was straightforward, there was no earth cable in the wiring, so I just added a small piece of earth cable, covered in a sheath, and screwed it to the metal backbox, and then to the earth-port on the back of the light switch.

I noticed on some of them, there was an earth wire already inside the set of wires, so you had a wire to common, wire to L1/L2, and then an earth wire going to the backbox.
So what I have done with those ones, is add an extra earth cable from the back of the light switch earth port, and then screwed it to the backbox where the existing earth cable is going, is this correct? Or should I have simply removed the earth cable from the backbox and plugged it straight into the back of the light switch earth socket? I guess it can't do any harm as it is, but I just wondered what the correct way would have been?

(I did notice there were existing metal switches in the kitchen, that had not been earthed prior to me replacing them!)


Edit - see my latest post, I HAD done it correctly all along :D
 
Last edited:
Pulsedriver said:
Anyhow, with some of them, this was straightforward, there was no earth cable in the wiring, so I just added a small piece of earth cable, covered in a sheath, and screwed it to the metal backbox, and then to the earth-port on the back of the light switch.
Click to expand...

If there was no earth in the cabling, then after running the earth from the faceplate to the backbox, what have you then earthed the backbox to?

The others where there were earths available you have done the correct thing. But i do not understand the above.
 
The second part of your post - switches with cables that do have an earth wire - you have done the right thing

What worries me is the first part of your post saying some switches didn't have an earth?? if i understand correctly so you just linked the backbox to the switch but its still isn't earthed and therefore should not have a metal switch fitted

unless your wiring is different ages at different switches then you should have an earth at all points but it maybe cut back / cut short, which could be extended and connected properly

If some of the switches have old wiring with no earth then you cannot fit a class 1 switch it should have plastic only or a specially designed class 2 metal switch that doesn't require an earth - these tend to be a plastic switch with a clip on decorative metal cover
 
Jez said:
If there was no earth in the cabling, then after running the earth from the faceplate to the backbox, what have you then earthed the backbox to?

The others where there were earths available you have done the correct thing. But i do not understand the above.
Click to expand...

Actually a very valid point... For some reason in my head I was assuming the metal backbox would act as an earth(!) with the reality being somewhat quite a different answer...! Hmmm... Although it was over a year ago I fitted those particular ones, and only yesterday the ones with existing earths, maybe I need to go and swap the older ones back, unless there is another way to earth them?
 
Jez said:
If there was no earth in the cabling, then after running the earth from the faceplate to the backbox, what have you then earthed the backbox to?

The others where there were earths available you have done the correct thing. But i do not understand the above.
Click to expand...
He has just connect the faceplate earth to the backbox!
Andi.
 
It's an early 1970's house, if that makes a difference re earth in existing wiring? The ones that definitely had earth in were on the kitchen extension which would have been wired in the late 90's I believe.

Well, there are 3 switches I need to check now, the others are definitely earthed correct, what annoys me, is that they were not previously earthed at all (and at least one was metal)!
 
Pulsedriver said:
Actually a very valid point... For some reason in my head I was assuming the metal backbox would act as an earth(!) with the reality being somewhat quite a different answer...! Hmmm... Although it was over a year ago I fitted those particular ones, and only yesterday the ones with existing earths, maybe I need to go and swap the older ones back, unless there is another way to earth them?
Click to expand...

Its possible that if you have old wiring with metal conduit it could be earthed through the conduit but would require testing to confirm cant just assume it to be earthed

Edit: ignore that - if you have early 70's built and original wiring there should be an earth maybe its just cut short?
 
I'll give the local electrician a call to come and check the other switches, we had the whole consumer unit upgraded last year to the newest spec (at the time) but even so I wouldn't want to rely on that tripping as a safety barrier!
 
Also, you need to consider that even though you connected the CPC (earth), to to the metalwork, is it actually earthed further up stream.

Been on a job today where, even though everything looked good in the switches and light fittings, everything metal actually had a potential of around 140volts to earth. could have been pretty nasty given the right (or wrong) circumstances.

If you had a new consumer unit fitted last year, the electrician should have picked up the lack of earth wires when he tested the installation after he fitted it and advised you on non compliances of the newer regulation.
 
Hey folks, well, I decided to check this morning before work, so went around unscrewing every single light switch that I had changed...

Oh well, I got it wrong, I HAD used the earth cable in all of them! I think what confused me was at the weekend I did 2 switches in the kitchen, which had an earth to the backbox (metal) but actually the rest of them upstairs that I had done, all had plastic backboxes, and the earth was already in the cable itself, and I had already connected it up correctly.

Lesson #1 never doubt yourself! (although always best to double check!) :D
 
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