Earthing a chrome light switch?

[kinkyboots]

Hi all, first post here. Just after a little advice so I know I'm safe and not gonna electrocute myself!

I've just bought some flat plate chrome light switches. Now I know metal face plates are supposed to be earthed but I assumed they'd include a bit of yellow-green sheathed wire with the switches. So I guess I need to buy some from somewhere. Is there any particular type/thickness of wire I'm supposed to use?

I have already checked and all the back boxes have earth wires. Some of them are the plastic hollow wall (non-metal) boxes, in which case the earths have been sleeved but not connected to anything. Do I just connect this directly to the new chrome switch or do I connect a new earth wire to these wires and then connect them all to some earth terminal somewhere?

The lights are LV downlighters in most rooms and mains voltage downlighters in the hall, all double-insulated so not earthed. I've looked into the ceiling cavity and the earths have been either bent back or twisted together.

Please can you advise if I can safely install these metal switches for the lighting circuits I have described and how to earth them (what kind of wire do I buy)?

Thank you.

 

[Space cat]

In a metal back box, the incoming earth wire should be connected to the box itself. Your switch will then be earthed through its fixing screws to the box - but you can always add an extra earth wire from the back box to the switch if you like.

With a plastic back box there may be nowhere to anchor the incoming earth wire. In this case you connect it directly to the switch's earth terminal.

If you want extra pieces of earth wire you can use wire scavenged from cable offcuts. Your local electrical supplier (small shop, not B&Q) might have a box of these going cheap. Look for some 1 sq mm (or maybe 1.5 sq mm) flat twin and earth. You can use all the cores (insulation removed) so a metre will do a lifetime of switches. You will also want some green/yellow sleeving.

 

[kinkyboots]

Thanks for your reply!

In a metal back box, the incoming earth wire should be connected to the box itself. Your switch will then be earthed through its fixing screws to the box

Oh I see - I thought you had to attach an extra bit of wire between the switch plate and the box itself when using a metal faced switch. You do say I can still do this though, perhaps this would be safer.

If you want extra pieces of earth wire you can use wire scavenged from cable offcuts. Your local electrical supplier (small shop, not B&Q) might have a box of these going cheap. You will also want some green/yellow sleeving.

The only bit of cable I've got lying around is some 1.0mm 3-core cable. Don't need it for anything - can I strip out the green-yellow core from there or is 1mm too flimsy? Otherwise I'll have to go somewhere like Maplin for a small amount of cabling.


Thanks again.

 

[SeanT]

It won't have a green/yellow core, unless it's flex, in which case you shouldn't use it for this. It'll have a copper earth wire in the middle, which you can sleeve green and yellow with some earth sleeve / "green" sleeving. It's always a good idea to add a bit of cable between, for when people take the switches away from the wall to decorate or such like (and tend to leave them like that for weeks on end....)

 

[kinkyboots]

Thanks for the reply.

Yeah sorry wrong terminology I guess I thought this stuff was called 3 core. I'm talking about the blue, brown and yellow-green sleeved copper twisted wiring that's all encased in pvc sheathing. Just wondered if the core that is already yellow-green sleeved could be used for this purpose, but I guess not then.

 

[ban-all-sheds]

Nothing wrong with using the G/Y core from flex as a flylead.

HOWEVER:

I've looked into the ceiling cavity and the earths have been either bent back or twisted together.

Please do not fit any metal switches until you've had the integrity of your lighting circuit earth checked. It's clearly been poked at in the past by someone incompetent, and you can't be sure that the cpcs at the switch positions are actually connected back to the earth bar in the CU....

 

[kinkyboots]

Please do not fit any metal switches until you've had the integrity of your lighting circuit earth checked. It's clearly been poked at in the past by someone incompetent, and you can't be sure that the cpcs at the switch positions are actually connected back to the earth bar in the CU....

Thanks but not what I wanted to hear.


What I mean is, where the downlighters have been installed only the live and neutrals go into the lamp fittings; the earth wire has not been used because these types of lights don't require earthing, so the earth wires have either been twisted together where lights have been daisy-chained, or just bent back on themselves with insulating tape and not used.

Where should the earth wires go if the lamp fittings don't need earthing?

This flat was built in the 80s so it's not particularly old wiring, if that helps.


What should I do? Can someone talk me through how to check the earthing, or is this a professional only job?

Just had the flat redecorated and wanted to install shiny new switches as the old white ones look awful now

 

[ban-all-sheds]

Thanks but not what I wanted to hear.

Where should the earth wires go if the lamp fittings don't need earthing?

Into connector blocks, particularly if they need to be joined. Anyone who just twists them together can't really be trusted to have done a proper job elsewhere, e.g. on the lighting loop circuit...

What should I do? Can someone talk me through how to check the earthing, or is this a professional only job?

As it's a flat you can't get access to the lighting cables by lifting floorboards above so the only option is to test at each light position and each switch with a low-resistance continuity tester.

Just had the flat redecorated

Fingers crossed that the circuit is OK, or that if not any problem areas can be easily found...

 

[kinkyboots]

Into connector blocks, particularly if they need to be joined. Anyone who just twists them together can't really be trusted to have done a proper job elsewhere, e.g. on the lighting loop circuit...

If I can get through the holes in the ceiling and put connector blocks on all the earths, is this sufficient?

As it's a flat you can't get access to the lighting cables by lifting floorboards above so the only option is to test at each light position and each switch with a low-resistance continuity tester.

It's a top floor flat so no, no floorboards above!

Low-resistance continuity tester - is this something I can pick up from Maplin and do the checks myself or is this still a job for a professional?

I just want nice clean shiny switches!!!



Thanks again for your help.

 

[SeanT]

Is there not a loftspace / void to access the ceiling?

 

[kinkyboots]

Is there not a loftspace / void to access the ceiling?

No, no loft. It's a top floor conversion flat i.e. what was originally loft space. Added in the 1980s so it's not ancient wiring. I don't want to add any more lights or anything, I'd just like to change the dirty old plastic switches for chrome ones but need to be sure that I can install these safely.

 

[kinkyboots]

Hi again, sorry to 'bump' this topic but I want to install these switches so can someone please advise if I can just go ahead and do this or not, or do I need to pay for an electrician to check all the earths? Thanks.

 

[ban-all-sheds]

I'm afraid the only way to be sure is to get an electrician to check it. You can DIY, but you can't buy a suitable tester in Maplin etc - unless you get lucky on fleabay the cheapest one I've come across is one that TLC sell for £104.58:

 

[kinkyboots]

I'm afraid the only way to be sure is to get an electrician to check it.

Cheers for the reply. Again, not what I wanted to hear! I thought fitting the switches was gonna be quick and easy.

Any idea of roughly how much I should expect to pay an electrician in central London to carry out these checks? If we're talking hundreds just so I can fit some chrome switches then maybe I should just forget the whole idea.

 

[Chri5]

Run a 'roaming' lead wire from the earth point for the flat (adj to the fuse board?) and then get a £10 multi meter with a continuity read out and / or buzzer.

This is a very, very basic test.........

Since you have one end of the roaming lead on a true earth, the other end one side of the meter probe, when you touch any of the earths / CPC's (that you not sure if the are connected back to earth)with the other meter probe you will complete a loop and thus the meter will read / give a continuity reading and / or buzz.

I've seen plumbers with door bells made up as a continuity buzzer to do exactly the same test .

Be aware that this doesn't show the quality of the CPC / earth conductor, but it will give you some assurance as to whether the earth / CPC is connected back to the main earth point / MET