I'm trying to replace a regular single pole light switch with smart light switch and I find the black wire coming from source to the switch but it's not terminating, it goes up to the ceiling. I stopped here because this didn't make sense. Can I get help on what's going on here?enter image description here

  • Does your smart switch need a neutral wire to work? – ThreePhaseEel Oct 15 '17 at 18:07
  • Yes it needs neutral wire for internal circuit to work. That's the white wire going straight, the instructions are clear on that I can splice it and cap it. Just not sure about the black running off to nowhere. – Amir Peracha Oct 15 '17 at 18:16
  • Normally those wires go into a cable clamp. Pretend they go into a pipe instead. Do this with the power off: Grab the three wires going out the top, and push them upward about an inch into the wall. . Do they freely move upward, or do they bind up right there at the cable clamp? I'm trying to figure out if you're in conduit. – Harper - Reinstate Monica Oct 16 '17 at 2:23
  • Got to agree with Harper's suggestion, metal box and lock nuts and or insulators look like the plot from info provided.+ – Ed Beal May 5 '18 at 23:08

There's more stuff on this circuit

The black wire you see running off to the top of the box is an always-hot that simply powers more things on the circuit, such as receptacles or other lights, while the red wire going up is the switched-hot to the light fixture this switch controls.

Cut and splice the white wire to the neutral from the smart-switch -- you'll have 3 white wires under this nut. Splice both black wires to the always-hot going into the smart switch. Splice the switched-hot from the smart switch to the red wire. Leave any 3-way or traveller terminals on the smart-switch capped-off or taped over.

As to the switch not fitting -- you'll have to finagle a single gang box extender (or a surface raceway starter box) into place and screw it to the box, then screw the switch to the extension. If the extender or starter box is nonmetallic, then you'll have to pigtail the ground on the switch to a ground screw on the back of the box, as well.

  • It's a single switch controlling single light fixture. Nothing else on this circuit. Can I terminate it here because there's nothing else on this circuit? – Amir Peracha Oct 15 '17 at 18:16
  • @AmirPeracha -- I wouldn't be so certain that there's nothing else on this circuit -- besides, that black wire is useful for future expansion (which is why it may have been put in to begin with) – ThreePhaseEel Oct 15 '17 at 18:28
  • Got it. Looks like I'll cap 3 white wires (1 from smart switch, 1 coming from bottom that I'll cut, 1 that's going up). And do the same for black live wire, 3 spliced and capped so if there is something on the same circuit it won't cut power to it. Make sense? – Amir Peracha Oct 15 '17 at 18:45
  • @AmirPeracha --exactly – ThreePhaseEel Oct 15 '17 at 18:47
  • Got it wired and tested. Now I can't fit the switch in the box :( – Amir Peracha Oct 15 '17 at 20:00

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