I have some lights controllable by two toggle switches on opposite sides of the room. Im located in the US in an older house, Im trying to install a Kasa Smart Dimmable 3-way Switch (KS230). However when I open both of the old toggle switches I only see 4 wires (1xBlack, 1xWhite, 1xRed, 1xCopper) (red opposite white, black opposite copper).

The Kasa seems to require 5 wires for the main (2xTravelers, 1xLine, 1xNeutral, 1xGround) but four for the satellite (2xTraveler, 1xload, 1xground). Why am I missing cables? How should it be wired up? Am I wrong for calling this a 3-way switch?

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Both switches have the same layout of wires, just one is upside down.

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  • 1
    Pictures of the switch wires and how they are connected will help a lot. Possible you just have two single switches and a three way will not work.
    – crip659
    Dec 28, 2022 at 22:27
  • If it's two single switches can smart switches be installed? I can't post pictures as they are too big, but the red is opposite the white and the black is opposite the copper.
    – Blueman101
    Dec 28, 2022 at 22:37
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    You need both hot and neutral in one of the boxes. Based on your description, you likely (but not guaranteed...) have one cable with either hot or switched hot + 2 travelers + ground. Which means the other switch may have what you need. Need pictures of both boxes/switches. Dec 28, 2022 at 22:38
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    Added another photo. There are 5 bundled cables coming into this box, 4 in the top and one in the bottom. The red and white seem to go into the one in the top right. The black goes to a different cable entirely. And the copper seems to be all bundled together from all the cables.
    – Blueman101
    Dec 29, 2022 at 0:10
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    Appreciate the help by the way. The black wire that spawns from the cable supplying red and white to my switch goes into a screw nut with many other black cables.
    – Blueman101
    Dec 29, 2022 at 1:19

1 Answer 1


Changing things a bit. Based on last question comment, the black going to the switch in box 1 is switched hot and the black going to the /3 cable is hot. With dumb switches, that's one of a number of possible, equally functional, configurations. But that won't work here - hot and switched hot need to be swapped.

Terminology: /2 = black/white/bare cable. /3 = black/white/red/bare cable. The individual colored things are called wires. The groups are cables. All grounds together and ignored for general purposes - they are important but since they all go together everywhere, they don't affect how things are connected.

Based on the pictures and description, what I believe to be the likely scenario is:

Box 1:

  • Remove the black wire from the switch. This wire is the switched hot. Put a piece of red tape on it.

  • Remove the black wire that is part of the /3 cable from the bunch of black wires. Put a piece of red tape on it.

  • Use a wire nut to connect the two "red" wires together. That takes care of switched hot - it now goes to switch 2.

  • Use a short piece of 12 AWG (14 AWG is OK if this is a 15A circuit) black wire to connect from the now-empty common screw on switch 1 to the bunch of black wires. *That takes care of hot - it now goes to switch 1.

That now leaves us with:

  • /3 = travelers (red and white) + switched hot (black)
  • Black on switch goes bundle of hots (incoming power distributed to multiple switches/locations) - "common" screw
  • Red and white on switch go to the /3 - the other 2 screws
  • Black from /3 goes to light fixture /2 cable
  • White from light fixture /2 cable goes to white neutral bundle
  • Use a short piece of 12 AWG (14 AWG is OK if this is a 15A circuit) white wire to connect from the neutral bundle to the switch, if the switch (as many smart switches do) requires neutral

In the case of adding a new wire to the black hot bundle or the white neutral bundle, you may need a new wire nut.

Box 2:

  • /3 = travelers (red and white) + switched hot (black)
  • Black goes to common screw
  • Red and white go to the other 2 screws

In box 1 you have hot, switched hot, neutral, travelers - everything you could need for any kind of switch.

In box 2 all you have is travelers and switched hot. You can't put a smart switch here unless it repurposes one of the travelers as an always hot and it doesn't require neutral.

If you want to improve things a little for future reference, mark the wires as follows:

Box 1:

  • Red and white on switch - mark both with yellow tape
  • Black from /3 goes to light fixture /2 cable - mark both with red tape

Box 2:

  • Red and white go to the other 2 screws - mark both with yellow tape

That way, looking at tape, and when no tape looking at the natural wire color:

  • Black = hot
  • White = neutral
  • Yellow = traveler
  • Red = switched hot
  • Hey, really appreciate your help with all this. The Kasa I'm trying to install has a main swich (which I think would go in box 1) requiring (2x travelers, 1xline, 1xground 1xneutral). However the satellite kasa only requires (2x travelers 1xground 1x load). Wouldn't that work in box2? The satellite doesn't require a common like the main switch.
    – Blueman101
    Dec 29, 2022 at 1:29
  • Correct. Satellite in box 2 Dec 29, 2022 at 1:41
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    That is line in this context. I don't really like the "line" term as much (won't explain here as it would only add to the confusion). neutral only ever gets white wires (except sometimes gray, but that's unusual). common in this context refers to the connection on a dumb 3-way switch which is not a switched position - i.e., power goes in common and out through one or the other (switched) travelers, or comes in on one or the other (switched) travelers and out on common. That is not to be confused with "common" as a rough synonym for "neutral" - which is a confusion that sort of comes Dec 29, 2022 at 2:51
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    about from the DC and small electronics world. Suffice it to say that if someone who knows what they're doing (I sometimes do...) says to connect a black or red or yellow or blue wire it will not be to neutral. So since I'm talking about connecting a black wire and your choices are "line" or "neutral", it can't be neutral so it must be line. Dec 29, 2022 at 2:52
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    Thanks so much for your help! Got it wired up and all working! Super awesome! Now one day I've gotta do the 3-way in the staircase (the other toggle in box 2 and a single toggle at the top of the stairs) but thats a project for a different day. Again thanks for the help!!!
    – Blueman101
    Dec 29, 2022 at 22:43

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