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I'm attempting to install a Kasa Smart 3 Way Switch (HS210). The installation instructions rely on the outlet box have two neutral (WHITE) wires being currently unused and wire-nutted together in the back of the outlet box.

When I took the plate off my the current switches (both of which control the same lights) this is what I found:

Box 1: There are two cables in this Box. One cable has a BLACK, WHITE and RED wire. The RED and WHITE wire go to the switch. The BLACK wire is under a wire nut with the WHITE wire from the second cable. The second cable has a WHITE and BLACK wire. The BLACK wire goes to the switch and the WHITE wire is under a wire nut with the BLACK wire from the first cable. [Going into the switch is a RED wire (top right), a WHITE wire (top left) a BLACK wire (bottom right) and a ground. In the back of the outlet box there was a BLACK wire and a WHITE wire, connected together by a wire nut.]

BOX 2: There is one cable in this box, with BLACK, WHITE and RED wires. [Going into the light switch is a WHITE wire (top right), a RED wire (top left) a BLACK wire (bottom right) and a ground. In the box, there is a no other wires.]

Coming off the KASA switch is a GREEN wire (labeled ground), a WHITE wire (labeled neutral) and than three screws: one labeled "load" and the other two labeled "travelers".

As mentioned, the instructions call for the outlet box having two WHITE wires connected together in the back box. Is there a way to safely install this if I don't have two WHITE wires, but do have a BLACK and WHITE wire connected together?

EDIT: Thank you for the replies. Edited to respond to the questions below. Here is a link to pictures of the boxes: https://drive.google.com/drive/folders/1OibESpeo_cEZXrPeIJdK1yjbl_s7ucUF?usp=sharing

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  • Unfortunately, switch positions don't mean much on 3-way switches - varies by brand and product. What colors are the screws on those switches (the "top left", "top right", etc.) - normal choices are black, brass, silver. Also, each of the switch boxes likely has 2 cables - can you match up (don't move anything, just tell us what you have) the black, white and (for one cable in each box) red - so that we know which wires are "together". Dec 12, 2021 at 20:59
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    Can you post photos of the insides of the boxes involved please? Dec 12, 2021 at 21:06
  • Is there a way to safely install this if I don't have two WHITE wires, but do have a BLACK and WHITE wire connected together? This sounds like "connect to the neutral bundle" - that may or may not actually be necessary. However, black and white together are definitely NOT neutrals! White in a cable can sometimes be hot, and that is quite likely the case here. But black can never (except really large sizes, not applicable here) be neutral. Dec 12, 2021 at 21:12
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    There is a way to configure an old (not smart) three way switch where one of the switches is on a switch loop and does not have a neutral available. Black connected to white is a sign you might have this configuration. It would help if you identified which wires come from which cables where there is more than one cable entering a box, and also the color of the screws they are connected to on the old switch.
    – jay613
    Dec 12, 2021 at 21:25
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    Switch positions don't help, they differ on every switch. Please go to the browser you posted your question on, and edit your question to tell us "how wires are grouped into cables" and 3-way screw colors. In fact, the 2 brass 3-way screws are for travelers, so feel free to just say something like "black and red from cable 1 are travelers". Dec 12, 2021 at 23:18

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Box #2 is the "far end" of your multi-way switch. The only wire is your 3-line cable with your hot (black) and two travelers (white and red).

Box #1 has the other end of this... but the problem is your other cable only has two wires. The white wire is being used as the incoming hot, as evidenced by

In the back of the outlet box there was a BLACK wire and a WHITE wire, connected together by a wire nut.

The black wire it's nutted to goes to the common screw of your "far" switch. So, you don't have a neutral in your setup. Your only real solution here would be to replace that wire coming from your fixture with a three-line cable (14/3 in this case). It would involve

  • Connect the new black wire where the existing 2-line white is for your incoming hot
  • Connect the red to where the existing 2-line black is for your incoming hot
  • Connect the white to the neutral at your fixture

The only other alternative would be to buy a switch that does not require a neutral.

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