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I have a workshop with a single switch that turns on and off two sets of lights. The first set is a row of spots and the second, at the other end of the room, is a fluorescent strip light. The wiring to the lighting is part accessible and runs on the top of wooden beams from which the lights are attached. The switch is fixed in a wall. Is it possible to put a second switch in that will turn off the spots? So I have the original switch that turns all on and off and then a secondary switch (mounted on the beam where the wiring is accessible) that turns on/off the spots and leaves the strip light on?

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There are a couple of ways to do what you want.

  • The gist is basically intersecting the spot light but allowing the power to not be interrupted when the existing switch is turned on. Simple enough. I've added two possible scenarios of how it might be wired. The spare neutral is required by code, but only if the ceiling is closed off and not accessible. It can be capped or taped off inside the switch box. Power In Switch Power In Light
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    Thank you so much - I really appreciate the drawings - the top one makes sense. I hope to get on with it this weekend. – Andrew Nov 27 '15 at 9:43
  • If the ceiling is not finished you can skip the spare neutral step. Otherwise, use 3 wire (black,red,white,green) for the run to the new switch. The drawing shows two whites for simplicity but the the dotted white would actually be the red. – Kris Nov 27 '15 at 13:25
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Is it possible? - yes, it's just rewiring. Is it easy? - Well that depends on how it's wired currently.

There will be a supply wire that brings in the "live" feed. From here, the live will go to the current switch, and a switched-live will go from the current switch to the lights, in parallel-wiring.

What you need is for there to be a switched-live wire which runs to all of the spots, but not to the strip light. In my linked picture for parallel wiring, if the spots are on the right, then the wire in the top right would match this description. All you need to do is cut this switched-live, to put an additional switch on it.

With this setup:

  • If current switch is "off", all lights are off
  • If current switch is "on" and new switch is "on", all lights are on
  • If current switch is "on" and new switch is "off", only strip light is on

I believe this is what you were aiming for.

  • @Andrew - Happy to help. Also happy to receive rep from upvotes for helpful answers :) Also, if an answer gives all the info you were looking for (I'm guessing that's Kris's rather than mine), feel free to give it the tick/check mark as your accepted answer. – AndyT Nov 27 '15 at 10:05
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In brief, all you need to do is put a simple on-off switch in series with the spots. The existing switch will then control power to the spots and the fluorescent but if the new switch is off, the power will not get to the spots. You should put the new on-off switch on the hot wire. There are many webpages that tell you how to find the hot wire, such as:
http://www.answers.com/Q/How_do_you_find_the_hot_wire_on_a_light_switch
If you put the on-off switch on the neutral wire by mistake, nothing terrible will happen, but you don't want to do that because you will be creating wiring that will be confusing to the next owner and somewhat less safe.

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