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I have a gang of 4 switch box, 3 switches are on the same circuit. There is no neutral or ground and it is knob and tube wiring, so I don't want to fix this (from what I've seen, the rubber/cloth housing looks good).

From what I understand, the reason for the neutral is to always have a closed circuit to power the smart switch. So I was thinking that if I put a smart bulb in one of the circuits and have smart switches in the other two, I should be able to wire the neutral to the smart bulb circuit.

So, changing this:

original wiring diagram

To something like this:

new wiring diagram

I have a feeling that the smart bulb load might get in the way of the neutral though. Perhaps I would have to remove the smart bulb out of the circuit and short that line, like so?

wiring diagram without one bulb

That wouldn't be optimal, but it is the least useful out of the bulbs as I have auxiliary lighting in that area. I would of course, would have to put some sort of documentation in the boxes to remember what I had done.

Is it possible (not necessarily with my circuits, but with a similar idea)?

Edit

FYI, all circuits are using dimmable LED bulbs, so an overload is not a concern. Ground would be floating, but that shouldn't be a concern as the switch plate would cover any exposed metal.

Edit 2

I am of course interested if what I am proposing is against code.

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So, given the comments, although electrically this would work, it is unsafe and a code violation. This is because the hot and neutral are to be in the same raceway to have the magnetic field of the hot wire cancel out the magnetic field of the return wire, and thus reduce any induction eddies in any nearby metal components. Such eddies could cause heat buildup and be a potential fire hazard.

It has also been brought to my attention that the dimmer that I had bought has no electrical safety standard certification such as CE, CSA or UL (or anything else for that matter). FCC is a radio emission standard, not a safety standard.

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  • Looks like a good summation of the commentary. Thanks for writing it up and being willing to learn and scrap your plans, no matter how good they seemed to you! Please be sure to give yourself a check-mark for this so others know it's got a "working" answer. – FreeMan Aug 3 '20 at 14:54
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    Yes, well done. Except CE is definitely not a standard certification - it's another junk mark they fake onto everything. (now if it was built by a maker inside the EU and you bought at a bricks and mortar vendor inside the EU, it might have some teeth, but anything made for the 120/240V market, CE is junk). – Harper - Reinstate Monica Aug 4 '20 at 16:58
  • @Harper-ReinstateMonica I've been reading up on CE. I'd have to get documents from the shop before I'd buy from them. – Adrian Aug 5 '20 at 0:03

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