This is a very similar question to one I asked yesterday, which Ryan Walkowski kindly helped out with.

This time, I'm looking for a some assistance in fitting a a single electric dimmer unit.

I am trying to replace my existing light switch with a LightWaveRF dimmer but am also have an extractor fan which powers on which this switch is on.

I took a guess but is anybody able to confirm the correct wiring (I'm in the UK) for such a setup?

Here are the old and new switches:

enter image description here

1 Answer 1


Technically that is the wrong switch for what its doing. That switch is designed to isolate both the incoming live and neutral. However i can see it has been jerry rigged per se as the incoming live and neutral at the top has been bridged to serve another purpose. You are going to have an issue with it. Are you able to indicate which of those cables goes where?

  • the dimmer pictured is rated for incandescent loads only. A fan is an inductive load. Two bad things will happen. First, the dimmer will overheat and fail , and second, the fan motor will most likely hum loudly and also overheat. A motor control device and variable speed fan motor would be required separately from the incandescent light dimmer. May 10, 2012 at 9:38
  • Thank you both for your input. Would it be easy to seperate them and use the existing switch to power the fan? If so, what would be the recommended approach? I guess (dangerously) that I'd have to feed the live into the right and use "S" to daisy-chain to the next switch?
    – Nick
    May 10, 2012 at 11:29
  • You could in theory use both switches side by side. Link the incoming live feed to the "L" terminal and to the "Supply L" of the normal switch. Then put only your light "Switch Wire" into the Variable terminal on the dimmer switch. You can then put the "Switch Wire" of the fan into the "Load L" side of the normal switch. This will work but its not ideal your fan will no longer come on when you switch on the light it will only operate on operating the old switch. And as the user says above do not connect the fan through the dimmer. May 10, 2012 at 12:23
  • 2
    Also do not use the "S" terminal its designed for connecting a like for like dimmer switch as a slave unit. May 10, 2012 at 12:25

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