Need an earth for new light - where to take it from?

doozerie

I bought a new external light to replace an existing one. The new one (a Steinel L626) has an aluminium body, it has an earth connection and the instructions with it have no mention of an incoming earth being optional. There is no earth wire to the existing light.

The fusebox is actually just on the other side of the external wall the light is mounted on. If I got an electrician in to sort this it might be a simple option for them to run an earth directly from there, but cost is a factor so that's my very last resort.

So I'm looking for an easier/DIY solution and wondering whether it is safe, and wise, to take an earth from an existing circuit. The nearest earth is in another light, but that light is controlled from an FCU which itself is a spur off a (radial) plug socket circuit.

I'm way out of my depth here, I don't know whether the earth is typically common across all circuits, or whether plug circuits and lighting circuits have separate earths, etc. So can I steal this other earth or is this a situation where I really have no choice but to get an electrician in?

The existing light also has a metal body incidentally, which might or might not be an issue, but the 1.5mm cables to are terminated in a connector strip and the metre long wires running from the strip to the light itself appear to be doorbell wire. The wire is exposed for about 30cm along an external wall before it enters the light, but it's wrapped in insulation tape over that 30cm, presumably for "safety". It's actually quite tempting for me to believe that I can't make things any worse, but...!

Edit: Forgot to mention that there appears to be no earth on the existing lighting circuit this external light is on. Admittedly I've only opened a coupe of ceiling roses to check that but I reckon they are representative of the lighting wiring throughout the house.

aido79

doozerie wrote: »

I bought a new external light to replace an existing one. The new one (a Steinel L626) has an aluminium body, it has an earth connection and the instructions with it have no mention of an incoming earth being optional. There is no earth wire to the existing light.

The fusebox is actually just on the other side of the external wall the light is mounted on. If I got an electrician in to sort this it might be a simple option for them to run an earth directly from there, but cost is a factor so that's my very last resort.

So I'm looking for an easier/DIY solution and wondering whether it is safe, and wise, to take an earth from an existing circuit. The nearest earth is in another light, but that light is controlled from an FCU which itself is a spur off a (radial) plug socket circuit.

I'm way out of my depth here, I don't know whether the earth is typically common across all circuits, or whether plug circuits and lighting circuits have separate earths, etc. So can I steal this other earth or is this a situation where I really have no choice but to get an electrician in?

The existing light also has a metal body incidentally, which might or might not be an issue, but the 1.5mm cables to are terminated in a connector strip and the metre long wires running from the strip to the light itself appear to be doorbell wire. The wire is exposed for about 30cm along an external wall before it enters the light, but it's wrapped in insulation tape over that 30cm, presumably for "safety". It's actually quite tempting for me to believe that I can't make things any worse, but...!

Edit: Forgot to mention that there appears to be no earth on the existing lighting circuit this external light is on. Admittedly I've only opened a coupe of ceiling roses to check that but I reckon they are representative of the lighting wiring throughout the house.

All of the earths go back to a common earthbar at the fuseboard so it shouldn't really matter where you take your earth from.
Would it be difficult to replace the doorbell wiring with 1.5mm as this should not be left that way?
Ideally you should have an earth at every light and switch but unless you are going to change any of them over to metal lights or switches them it shouldn't be a problem.
I'm guessing it's an older house so that could be something to look at if you ever decide to rewire it in the future.

doozerie

aido79 wrote: »

All of the earths go back to a common earthbar at the fuseboard so it shouldn't really matter where you take your earth from.
Would it be difficult to replace the doorbell wiring with 1.5mm as this should not be left that way?
Ideally you should have an earth at every light and switch but unless you are going to change any of them over to metal lights or switches them it shouldn't be a problem.
I'm guessing it's an older house so that could be something to look at if you ever decide to rewire it in the future.

Thanks for the info.

Re the doorbell wiring, yes, I have appropriate outdoor cabling to swap in place of it. It should be a simple enough swap as access is easy and it's a short length.

The house was built in 1981 but the wiring, much like many aspects of the house, seems to have been a victory of convenience/speed/cost over quality. It looks like some very dubious changes were made to it over time too so it's a bit of a dog's dinner that might need the skills of a professional electrician at some point in the future. For now I'm addressing the simple things that are within my capabilities as I find them.

I've not yet encountered an earth at any of the (4) lights or (6) switches that I've opened. Some of those switches are metal. And one of the metal switches, a 3-gang, is a rat's nest of wires, amongst which are a neutral and a live from a plug socket - why anyone would do that is beyond me, especially as there is a lighting circuit live feed in there too although I've no idea which was there first. I'm postponing tackling that one for a while.

As a matter of interest, given the lack of earth, is it advisable to replace all metal switches with plastic ones?

aido79

doozerie wrote: »

Thanks for the info.

Re the doorbell wiring, yes, I have appropriate outdoor cabling to swap in place of it. It should be a simple enough swap as access is easy and it's a short length.

The house was built in 1981 but the wiring, much like many aspects of the house, seems to have been a victory of convenience/speed/cost over quality. It looks like some very dubious changes were made to it over time too so it's a bit of a dog's dinner that might need the skills of a professional electrician at some point in the future. For now I'm addressing the simple things that are within my capabilities as I find them.

I've not yet encountered an earth at any of the (4) lights or (6) switches that I've opened. Some of those switches are metal. And one of the metal switches, a 3-gang, is a rat's nest of wires, amongst which are a neutral and a live from a plug socket - why anyone would do that is beyond me, especially as there is a lighting circuit live feed in there too although I've no idea which was there first. I'm postponing tackling that one for a while.

As a matter of interest, given the lack of earth, is it advisable to replace all metal switches with plastic ones?

Having a neutral and live from a socket to a lighting circuit would suggest to me that there is no RCD protection on the socket circuit which is dangerous in itself. It may not be the case but if they have only used the neutral from the socket circuit and the live from the lighting circuit it may be difficult to rectify this.

The metal switches are unlikely to become live but it is a possibility and it is definitely not ideal to have unearthed exposed metal parts in any electrical installation so it may be a good idea to replace them either plastic ones. It's possible to get plastic switches with metal covers which won't need an earth if you still want the metal look.

doozerie

aido79 wrote: »

Having a neutral and live from a socket to a lighting circuit would suggest to me that there is no RCD protection on the socket circuit which is dangerous in itself. It may not be the case but if they have only used the neutral from the socket circuit and the live from the lighting circuit it may be difficult to rectify this.

Some further info that might clarify the state of the wiring: Of the 3-gang metal switch one rocker controls ceiling lights in the kitchen, and the live for this is on the downstairs lighting circuit. The other two rockers control under-cabinet lighting (strips) and in-cabinet lighting (downlighters) on each side of the kitchen, the live for these is from the plug socket (which itself is a spur off a plug socket on a radial circuit).

So behind that 3-gang switch is quite a collection of cables. I only opened it briefly and quickly closed it up again when I discovered the two different lives. I'll need to check it again but I think the neutral from the plug socket was either taped off or connected directly to another cable which itself is not connected to the switches i.e. I don't think the plug socket neutral is connected to anything within the 3-gang, but I could be wrong.

Edit: ah, I just realised that I haven't given any thought to the neutral to the lights, looks like I have more wire tracing to do. Thanks for the pointer.

aido79 wrote:

The metal switches are unlikely to become live but it is a possibility and it is definitely not ideal to have unearthed exposed metal parts in any electrical installation so it may be a good idea to replace them either plastic ones. It's possible to get plastic switches with metal covers which won't need an earth if you still want the metal look.

Both that 3-gang metal switch above and a 4-gang metal switch appear to be made by MK (just judging by shape of covers and switches, look like Logic Plus switches, I'll have to check that properly by opening them up fully again). If they do have markings verifying them as MK then I'll check their specs to see whether they need an earth.

There are a few other metal switches with no discerning (to me) features so I'm not sure I'll be able to find and check any specs for those, so I'll replace them with plastic switches just to be sure.

aido79

doozerie wrote: »

Some further info that might clarify the state of the wiring: Of the 3-gang metal switch one rocker controls ceiling lights in the kitchen, and the live for this is on the downstairs lighting circuit. The other two rockers control under-cabinet lighting (strips) and in-cabinet lighting (downlighters) on each side of the kitchen, the live for these is from the plug socket (which itself is a spur off a plug socket on a radial circuit).

So behind that 3-gang switch is quite a collection of cables. I only opened it briefly and quickly closed it up again when I discovered the two different lives. I'll need to check it again but I think the neutral from the plug socket was either taped off or connected directly to another cable which itself is not connected to the switches i.e. I don't think the plug socket neutral is connected to anything within the 3-gang, but I could be wrong.

Edit: ah, I just realised that I haven't given any thought to the neutral to the lights, looks like I have more wire tracing to do. Thanks for the pointer.



Both that 3-gang metal switch above and a 4-gang metal switch appear to be made by MK (just judging by shape of covers and switches, look like Logic Plus switches, I'll have to check that properly by opening them up fully again). If they do have markings verifying them as MK then I'll check their specs to see whether they need an earth.

There are a few other metal switches with no discerning (to me) features so I'm not sure I'll be able to find and check any specs for those, so I'll replace them with plastic switches just to be sure.

The neutral should not be connected to anything in the 3 gang switch but if it not going to the lighting circuit, which it wouldn't appear to be from what you have said, then it shows that the socket circuit has no rcd protection which is dangerous.
Changing the switches to plastic switches is probably a good idea for now anyway. If a switch is metal it needs an earth regardless of what the specs say.

doozerie

Is it possible to test (as a DIYer) whether the socket circuit has RCD protection?

aido79

doozerie wrote: »

Is it possible to test (as a DIYer) whether the socket circuit has RCD protection?

The first place to look would be at the fuseboard to see if you actually have RCD's installed.

If you have a live going to one circuit and the neutral from that same circuit coming from a different circuit then electrically it is not possible to have RCD protection as the Rcd works on the principle that an imbalance between the live and neutral will trip the RCD.

doozerie

aido79 wrote: »

The first place to look would be at the fuseboard to see if you actually have RCD's installed.

If you have a live going to one circuit and the neutral from that same circuit coming from a different circuit then electrically it is not possible to have RCD protection as the Rcd works on the principle that an imbalance between the live and neutral will trip the RCD.

There is an ELCB on the same row as the MCB's for the socket circuits. The ELCB works, as I tripped it accidentally while wiring up new plug sockets (with the corresponding MCB switched off), but that was on a different socket circuit so I guess I can't take any comfort from that.

Looks like I really need to trace the wiring further. I *think* the socket circuit is okay and that it's the lighting circuit, and perhaps other circuits, that are in question - that is based on preliminary checking which suggested the socket radial circuit was fine, direct cabling from socket to socket, with a live and neutral running from one of those socket to a spur/socket. The mess kicks in with that latter spur/socket, which supplies a live and neutral onwards to the 3-gang light switches.

I'd been thinking I'd just remove/cut back the live and neutral between that socket and the 3-gang, but your posts made me realise I'd not given any thought to where the neutral may be running to - hopefully it is terminated in the 3-gang backbox, but I'm not sure, and if it's not it could be running anywhere else in the kitchen, either to the lights or to something else.

aido79

doozerie wrote: »

There is an ELCB on the same row as the MCB's for the socket circuits. The ELCB works, as I tripped it accidentally while wiring up new plug sockets (with the corresponding MCB switched off), but that was on a different socket circuit so I guess I can't take any comfort from that.

Looks like I really need to trace the wiring further. I *think* the socket circuit is okay and that it's the lighting circuit, and perhaps other circuits, that are in question - that is based on preliminary checking which suggested the socket radial circuit was fine, direct cabling from socket to socket, with a live and neutral running from one of those socket to a spur/socket. The mess kicks in with that latter spur/socket, which supplies a live and neutral onwards to the 3-gang light switches.

I'd been thinking I'd just remove/cut back the live and neutral between that socket and the 3-gang, but your posts made me realise I'd not given any thought to where the neutral may be running to - hopefully it is terminated in the 3-gang backbox, but I'm not sure, and if it's not it could be running anywhere else in the kitchen, either to the lights or to something else.

It sounds like your wiring is probably ok but it wouldn't be a bad idea to find out where that neutral goes. You can get cheap RCD testers on ebay which will be good enough for DIY purposes. It is possible to make a home-made one but I'm not going to tell you how because it is kinda frowned upon and you would be better off with a tester that is purpose made.

whizbang

This molehill is competing with everest at this stage..

Is the light out of reach by any chance ?

aido79

whizbang wrote: »

This molehill is competing with everest at this stage..

Is the light out of reach by any chance ?

That may solve the issue with the outside light but what has it got to do with unearthed metal switches and possibly non rcd protected sockets?