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I have a 4 season room with some lights but the switch is in the kitchen. I installed a 2-gang box in the room and ran a 3-wire romex wire from the new box to the existing box (they are on the opposite sides of the same wall), and am trying to connect it in a 3 way configuration so I can turn the light on or off from either switch.

Below is a photo of the existing box in the kitchen. A1 and A2 were connected in a single pole configuration. B1, B2, and B3 are from the new wire going between the boxes. When I turn the power on and test the wires with my non-contact tester, the white wire A1 is live and the black wire A2 is not, which I was not expecting. I can't seem to get the wire configuration right so I'm hoping someone can tell me how to wire these up properly. I'm using Legrand Adorne paddle switches (instructions here). Thanks in advance.

wiring photo

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    Am I correct that wires A1 and A2 go into the same cable? Also can you get some black tape and yellow tape? – Harper Jul 23 at 2:25
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    Also red tape if you can get it. This should be electrical tape. Shrink tubing will also suffice. – Harper Jul 23 at 2:27
  • Can you post a photo looking into the back of the box? – ThreePhaseEel Jul 23 at 2:52
  • @Miles Budnek's diagram answered it for me, thanks for your help. – Vincent Jul 23 at 3:37
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It looks like your current switch is on a switch loop. The wires you've labeled A1 and A2 are not neutral and hot, they are always-hot and switched-hot.

That means that to convert this to a 3-way configuration, you need to wire it like this:

3-Way Wiring Diagram

As @Harper pointed out in the comments, since A1 and B2 aren't acting as neutrals, you should mark them with black electrical tape to designate them as hot. It's also a good idea to mark the ends of B1 and B3 with yellow electrical tape to flag them as travelers to make it clear what purpose they're serving as well.

I've not drawn the grounds in my diagram, but they should be connected to all of the other grounds.

  • Excellent, that did it! One more question: the other switch to go in this new box is a new single light fixture in the room with a wire going from the light to the new box. If I want to power this switch separately, can I do that off this or should I use one of the other switches in the box? – Vincent Jul 23 at 3:35
  • You should ask that as a new question. You will not be able to connect a new light to your 3-way switch wiring. I can't tell from your photo if there's anything in the current box you could use or if you'll need to run a cable to an existing light or outlet box. – Miles Budnek Jul 23 at 4:04
  • The "neutral" wires must be marked with black tape to indicate they are hots. Further, one would be wise to mark the 2 travelers with yellow tape,as a letter to your future self of what exactly is going on in this box. – Harper Jul 23 at 4:13
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    @Harper Updated to add that – Miles Budnek Jul 23 at 4:26
  • So just going back to this - I originally wired it with a 3way paddle switch and wanted to know if I could use a dimmer instead. The LeGrand Adorne Tru-Universal dimmer requires a neutral. Is it not possible to use this dimmer with this configuration? Thanks. – Vincent Sep 3 at 0:21

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