My new construction house has front exterior lights (both hardwired and standard bulbs) controlled by a single switch. I'd like to upgrade the switch into a smart switch. Attached is a picture of the wiring - the switch in question is on the left that I'm holding, the other controls interior lights. I see 1 bare wire (ground I'm guessing?), 1 red, and 2 black. There are white wires inside the box but not attached - are these neutral wires I can use for the smart switch? Any special considerations I need to keep in mind? Thanks!

switch is on the left

  • Are you sure they are simple single pole switches? Is there another screw(besides the ground) on the other side of the switch with two blacks and a red?
    – crip659
    Jul 19, 2023 at 13:14
  • Darn crip659, I didn't notice that the aswitch may be a 3 way.
    – RMDman
    Jul 19, 2023 at 13:31
  • 1
    @RMDman The black screw is one clue plus if both switches match, both have the extra screw. Now to see if they are being used as three ways or singles.
    – crip659
    Jul 19, 2023 at 14:10
  • @crip659, if only there was complete info with the questions...lol Yeah I should have noticed the black screw. I was quick to assume it was single pole. read the question rather than paid attention to the pic.
    – RMDman
    Jul 19, 2023 at 14:20

1 Answer 1


Assuming the wiring is all common US.

The white wires are neutral. You can use that bundle for the Smart switch.

The red goes to the lights. It's switched.

The 2 black wires are power from the breaker and relayed to continue the circuit. They need to be connected and add a pigtail wire to connect to your smart switch.


If the switch is 3way you will need to find which of the black wires is hot from the breaker and attach that to the smart switch. Cap the other black wire. This will also make the other switch in the circuit inoperable.

Bare copper is ground.

You should be good to go

  • Thank you so much for the help! I was able to verify that, yes in fact, this is a 3 way switch. (The other switch was in the garage - would never have guessed if I hadn't gone looking.) So then I suppose my follow-up question to your answer is - how do I determine which of the black wires is coming from the breaker? Thank you!
    – Henry
    Jul 22, 2023 at 1:09
  • I used a multimeter and found that actually with the switch off, the red wire is reading 120V and both blacks are 0... with the switch on, the black wire under the red wire is 120V (the other black stays 0, and the red stays 120). That would mean that actually the red wire is the line, and the one black wire underneath it is the load, right?
    – Henry
    Jul 22, 2023 at 11:22
  • Yes that is correct those are the 2 wires to connect to the smart switch with a neutral and ground. Cap the remaining black wire with a wire nut. The switch in the garage will have to stay in the same position for everything to work. maybe place tape on it so others don't bother it.
    – RMDman
    Jul 22, 2023 at 12:44

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