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I'm replacing an old 3-switch switch in the bathroom with a new one. The old switch has a "Common" terminal (black wire) and 3 unlabeled terminals (one white and two black wires). I also have one unconnected copper wire coming out of the wall, which I presume is Ground, but not sure.

The problem is that the new switch has a "Line" terminal, in addition to a green "Ground" terminal, and three unlabeled terminals. So the old switch had 3 terminals, and new one has 4.

I've tried a few combinations but none cause the switch to work. Any ideas?

Note: Old switch is from a French company, Hubbell.

3 wire switch

  • Can you post a photo of the inside of the switch box? – ThreePhaseEel Aug 13 '17 at 23:35
  • @ThreePhaseEel Done. – osman Aug 13 '17 at 23:47
  • Can you pull all the wires out of the box and get us a photo that shows which wires go into which cables? – ThreePhaseEel Aug 13 '17 at 23:48
  • I've tried the best I could, but to summarize: -Top left black wire, white wire, and bare copper come out of the white tube. -Bottom black wire comes out of a black tube (let's call it Tube A). -Top right black wire comes out of a different black tube (let's call it Tube B). -A white wire comes out of Tube B and is connected (via electrical tape) to a white wire coming out of Tube A. – osman Aug 14 '17 at 1:10
  • Is rerunning wires an option here? – ThreePhaseEel Aug 14 '17 at 1:34
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Fixing the sins of installers past

What the installer who put this switch in did is run two /2 NM cables between the switch and the junction box downstream of it to hold all the switched hots and the neutral, which was rather naughty of them as it is a likely NEC 300.3(B)/310.10(H) violation that could get your switch box mighty toasty if the circuits the triple-switch was controlling were heavily loaded.

What they should have done, and what your electrician (as you indicated you weren't comfortable running wire yourself) needs to do to fix it, is run a /4 W/G NM cable from the switch box to the first downstream junction box -- that cable has enough wires in it for the neutral, the ground and all the switched hots, combined into one sheath. Then, they can put the new switch in and have the installation (or at least, this part of it) meet Code :)

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Looks like a plaster wall which could explain why it is an "unconventional" setup due to wall repair cost associated if they ran proper wiring after it was built.

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