I am trying to install a Kasa HS210 smart switch in my basement/garage. 5 light fixtures are installed in the ceiling with led lights attached. There are 3 switched controlling these lights, a three way switch at one each end and a 4 way in the middle. When the smart switch is activated, the lights flash off and on. I then have to switch both of the other switches to get them to turn back off.

I ordered an additional switch to make sure it wasn’t a bad switch and got the same results.

The first three way switch has white connected to the black screw and red and black travelers. There are no commons in this box. There is an additional switch going to an outside light.

switch 1

The second switch is a four way with the red and black travelers. There is another three way switch on a different circuit going to a stairway.

switch 2

switch 3

The smart switch is in the third location. There is another switch in this box going to an outside light. These are on the same circuit.

switch 2

switch 3

  • I haven't looked up details for this particular switch, so just comments for now. But possible key issue: A typical smart switch needs constant power ("hot"/"line") and neutral (what you are calling "commons") and some form of (i.e., possibly direct, possibly through other switches a.k.a. travelers) switched hot. Based on the description, it sounds like you have the switch in a location where it does not get constant hot, only travelers, neutral and switched hot. In other words - it would need to go at the other end. Feb 20, 2023 at 19:05
  • The other end appears to be a switch loop, so it can't possibly go there. The location looks as good as it's going to get; my question is whether the Kasa instructions were followed, as how any given smart switch treats the other wires varies a lot. Following instructions is mandatory NEC 110.3. Feb 20, 2023 at 19:23
  • So I guess I will return the switches and go back to how it was.
    – Mjimsr
    Feb 20, 2023 at 22:14

1 Answer 1


I have the Kasa HS210 and it was very difficult determining where and how to place it. I have a question here about it and answers weren't very clear except a strong suggestion to "test it out."

With the help of an electrician friend, photos of the "before" wiring and tape labels on each wire (and after shutting off the breaker), I disconnected BOTH 3-way switches. We turned the breaker back on, and checked the wires with a multimeter.

Once we found line hot, we knew that's where the switch should go (out of 3+ insulated wires at each end, this will be the only one at 120V to ground).

Then we identified the travelers for each side and re-taped them yellow. At that point it's just making sure you have neutral (easy for my house, built in '09) and finding a faceplate that fits these massive Decora-style switches.

  • I sent back the Kasa switch and replaced the lights with smart bulbs. Problem solved.
    – Mjimsr
    Feb 22, 2023 at 15:47

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.