I have an existing 3-way switch. The pair of switches control my hallway light and works perfectly. To replace this, I bought a Kasa Smart 3 Way Switch HS210. Other than the copper wire , it has only three colored wires. Black, red and white. When I read the manual for the Kasa switch, it says it needs 4 colored wires. Do you know how to make this work ? I am trying to understand how the current switches work. Which colors are the traveller wires (both white and red, with no neutrals) ?

I am fine with sacrificing the 3-way nature if needed but I need to control this with a smart switch. So its ok if I can just replace one of them with just a smart switch if required. I can post more photos after disassembling if you have questions.

Update: I added the two pictures for the existing 3-way switch wiring. The red and black wire are on the right. The white and copper are on the left.

Left side of the switch

Right side of the switch

2 Answers 2


You don't get to choose which 3-way

The nature of your house wiring will dictate to you which 3-way switch can be replaced with a smart-switch "master". TLDR: it isn't this one, which is why you're here asking instead of buttoning up a successful installation.

There are at least five ways to wire a 3-way installation, so I can't promise this is so for every one - but at least 80% chance, you will be able to successfully install the smart 3-way at the other switch location.

What to do at this location depends what the instructions the smart 3-way comes with. Either you retain the original 3-way switch, possibly change its wiring slightly, and/or you install a companion/servant smart switch, which communicates with the master in one way or another. This varies - some use the 3rd wire, and others use radio or induction on the power line. A few even use radio, and run on battery, allowing you to install a 3-way remote where no electricity is in the wall. It still sits in a proper junction box, they're not those gimpy handheld remotes that come with cheap appliances.

If you have a particular preference, e.g. if you want a full-featured servant that gives all the functions of the master with no compromises, that's available on the marketplace from some vendors.

  • @harper-reinstate-monica, thank you ! I added two pictures which show the exact wiring. Does this mean my wiring does not have a neutral wire ?
    – John
    May 2, 2023 at 2:04
  • @John -- you'll need to check the other switch in this 3-way setup May 2, 2023 at 2:25

Answering my own question. I had a 3-way switch working. What I was not finding was the neutral wire. What I had to do was open both boxes and check for the neutral wire somewhere inside the box. In my case, the white neutral wires were not connected to the switch but were in the box inside the wall. So to install the 3-way smart switch, I had to connect the neutral wire from the new switch to the 2 other neutral wires and everything worked!

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