Single switch to double switch

napper

I’m putting external lighting around the garden.
I have an external light above the back door with the (single switch on the back wall)
I have installed all the external lights and looped them back to the house. My intention was to change the single light switch to a double and work the existing external light and the new lights off the double switch.

I have encountered a problem though. There are 3 live wires running to the existing switch (2 into com & the other into L1)

The cable I ran the new lighting from back to the house has a live, earth and neutral.

Any advice on how to wire up the double switch would be appreciated

Calahonda52

Nice runners!

Take off the cover off the light and see whats up there?

I am not a sparks and lot of them are here

When the external light is off my guess is that the pair of wires is the live and the single is the switched live to the external light, with the neutral at light

GreeBo

Yeah looks like the live is going into to switch and then off somewhere else.

The light is switched on the live only, you would need to get a neutral from somewhere else, typically all the neutrals would be linked at the light fittings. Since you have fed the new wire behind the wall, does it pass near an existing light that has a neutral that you can tie into?

Other than that, you would put the "2" existing live wires into Com 1, then a loop from Com 1 into Com 2 to give the other circuit a live wire. Then existing L1 into L1 and the live from your new lights into L2 and of course earth with the existing earths.

Calahonda52

GB, am I right in saying that he can't use a power circuit neutral if he had one to hand?

rob w

https://www.boards.ie/discussion/comment/122613443#Comment_122613443

Never mix neutrals like that across circuits. It'll trip the RCD anyway if the neutral is taken from a socket.

Without a neutral you're pretty stuck there. You don't need to just get a neutral from somewhere, you need one from that lighting circuit that's feeding the switch.

rob w

You could potentially spur off an existing socket circuit with a fused spur, 3A or so depending on load and do it that way.

That looks like a flex cable though, not suitable for outdoor lighting. Is that what's been looped around the external lights?

napper

Thanks for the prompt feedback folks, I’ll check the existing outdoor light for a neutral.

It is a flex that in the photo but it only goes to the junction box on the other side of the wall where it connects to external grade cable, this then feeds the new external lights.

I should have checked the switch before starting all this I guess.

I didn’t want cable exposed and running along the external wall connecting to the existing light. I wanted to keep the two on separate switches and the new cabling hidden as much as possible. I was finally able to use the piping I installed under the paving 14 years ago for just such a project and run the cable underground 🤦‍♂️

napper

https://www.boards.ie/discussion/comment/122613468#Comment_122613468

This is the existing external light that goes back to the switch in the previous photos

standardg60

Would it be feasible to try to fish a neutral alongside the live from light to switch and connect at each end?

napper

https://www.boards.ie/discussion/comment/122622754#Comment_122622754

I couldn't find a neutral in the wall near the live wires. Is it possible that it just loops from the existing external light along the ceiling to another internal light?

meercat

this external lighting should be rcd protected. It’s unlikely that the lighting circuit you are trying to connect to has rcd protection (unless it’s a relatively new electrical installation)

as there’s no neutral at the light switch my recommendation is to connect to a socket circuit (as rob w has said previously)using a 3amp switch spur outlet.

Rob w also mentioned that this cable is unsuitable for outdoor use

standardg60

https://www.boards.ie/discussion/comment/122622843#Comment_122622843

Yes the neutral most likely is dropped down from above. The live from the switch should be in a conduit going to the light, so you might be able to feed a neutral back along it from the light, connect to the neutral bank at the light to your flex neutral.

It's a common misconception that light switches are the same as sockets but because they only control the live feed side they don't have neutral wires.

carveone

https://www.boards.ie/discussion/comment/122613468#Comment_122613468

Don't get me started! It means that you're working on an isolated circuit and are holding the neutral in your hand and wondering, sure where is that other wire coming from now. And your brother turns on the light on another circuit and hey presto, the light doesn't turn on but you do. 😊

RCDs are great really.

carveone

https://www.boards.ie/discussion/comment/122622843#Comment_122622843

Yes. This might give you an idea of what you are seeing:

https://flameport.com/electric/lighting_circuits/lighting_loop_at_switch.cs4

In your case it seems the neutrals are connected at the actual light instead of having the extra junction shown in that website.

I'd agree with meercat on the RCD protection - you don't want a situation where an external light gets damaged or wet and the only protection from shock is an MCB.

napper

https://www.boards.ie/discussion/comment/122622959#Comment_122622959

Thanks for your reply meercat.

I have nym-j cable running from the new up/down lighting in the back garden up to the the house. The cable in the photo (the flew cable) literally goes from the switch, through the cavity to the outside juntion box where it connects to the nym-j cable.

I reckon I can run cable from a socket over to the switch in the photo and keep it consealed behind the skirting.

napper

https://www.boards.ie/discussion/comment/122623053#Comment_122623053

Timber frame house, no conduit used anywhere. Built in 05/06 at the height of the boom, just before the crash! Shortcuts weren't uncommon!😥

napper

https://www.boards.ie/discussion/comment/122623377#Comment_122623377

No conduit means the wires are passed through the studs and obviously makes it next to impossible to pull a wire through

rob w

https://www.boards.ie/discussion/comment/122623315#Comment_122623315

If you are going to spur off the socket, don't run that cable to the light switch. You will want a separate box for a switched fused spur.

You don't want the socket circuit and the lighting circuit wiring in the same switch box.

napper

Meant to update sooner.

Got this sorted, thanks for the help & advice 👍🏻

Calahonda52

https://www.boards.ie/discussion/comment/122647867#Comment_122647867

How?

napper

https://www.boards.ie/discussion/comment/122648246#Comment_122648246

I did as rob w suggested, spurred off an existing socket circuit with a fused spur, 3A