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This is probably not possible and instead just highlights my basic lack of understanding, but thought it was worth asking! If it is possible I would get a qualified electrician to do it.

I'd like to install a smart wifi dimmer switch which requires a neutral wire, but I don't have a neutral. (I've already got a smart dimmer that works without neutral, but want a nicer one that does require it).

The switch in question is a 2 gang switch. One switch controls my kitchen spot lights, the other controls an outside light that we've never used.

I've read that the reason for a neutral is so that the wifi switch can draw power to run itself even when the light circuit is broken. So I was wondering if in the absence of a neutral wire, the redundant wires for the outside light could be made to provide power for the wifi switch.

I'm in the UK. 100+ year old house, but wiring is this millenium.

My current switch has a L, L1 & L2. Two wires go into the L.

The new switch has a L, L1, G, N.

The box in the wall has an earth wire looped into the casing.

Photo of box:

Photo of box

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  • A photo of what is going on inside the junction box would be helpful. Don't unhook any wires! You can edit photos into your question. – Harper - Reinstate Monica Nov 8 '20 at 18:11
  • Thanks @Harper-ReinstateMonica, photo added (photos.app.goo.gl/5DEAZYQvgbaNjQMN6) – Jamie G Nov 9 '20 at 9:52
  • Please use Home Improvement's own hosting to embed your images directly into the question so people don't have to go rummaging around and clicking links to get to yours. Just click the "sun & mountain" icon above the text box & drag the images in or paste links. – FreeMan Nov 9 '20 at 12:02
  • @FreeMan I feel like the switch box photo is secondary information for this question and so didn't want it showing up by default. In retrospect I feel I should have just left most of the current switch / new switch info + the photo in the comments instead of in the question, making the question more generic. But probably not worth removing now! – Jamie G Nov 13 '20 at 19:50
  • @JamieG the more specific you can make it, the more likely you are to get good advice for fixing your situation. While general advice, is generally good, it obviously wasn't enough for you (I presume you did some searching and came up with general advice), so specifics really are required. – FreeMan Nov 13 '20 at 22:43
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In the absence of any other answers I'll put what I'm thinking currently. Please tell me in the comments why this will cause my house to burn down (and also vote me down while you're at it). Or even better, help me improve the answer or give a better solution that actually works :)

My idea

The second gang goes to a light socket that is not in use. I presume that in this light socket there will be:

  • one set of wires that goes to my fuse box and will include a live (A) and a neutral (B). I don't know if there'll be an earth (C) too?
  • and another pair of wires that go to the switch. We'll call these (D) and (E)

In the redundant socket

  • Cap off (A)
  • Join (B) to (D)
  • Cap off (E)

In the switch

(connections on the actual switch are L, L1, G & N)

  • Cap off (E)
  • (D) will become a neutral wire and can connect to N
  • The two wires from Gang 1 can connect to L & L1.
  • Join the current earth that's looped into the box to G using an extra bit of wire

Result

Job done? Or 🔥🔥🔥?

In the absence of doubt, this "answer" should not be thought of as an answer yet and will not be accepted unless enough people with more knowledge than me confirm it's safe. And... I'd still get a qualified electrician to actually do the work.

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