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At present we have a switched outlet for a floor lamp. I would like to replace this with a Kasa smart switch.

When I pulled the switch out I noticed it had 2 black wires and 1 red wire:

enter image description here

The red wire is back-stabbed into the switch, and one of the black wires is back-stabbed while the other is attached to the screw terminal.

Looking at some threads (e.g. Changing old light switch 2 black wires and 1 red) and some other research, it looks like for that use case the recommendation was to create a pigtail. But because this is a switch for an outlet I'm not sure if the same approach would apply.

The smart switch I have calls for 1 neutral (white), 1 green (ground), and two black wires. But I have 1 red, 2 blacks, a neutral (not shown), and a ground (not shown; wired to the box). What the approach for this be to cap the two blacks and create a pigtail, and connect that pigtail to one of the black wires for the smart switch? And then connect the red to the other black wire on the smart switch?

old switch                new switch
=================         =================
black --+
        |---pigtail-----> black wire
black --+
white            -------> white
red              -------> black wire
copper (ground)  -------> green (ground)

Thank you.

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  • Is the Kasa switch a dimmer or is it only on/off? Does it have a UL or ETL listing/logo/stamp? (CE means China Export; not good enough). Jan 17 at 21:51
  • You don't need to mess with the ground wires. The switch will pick up ground via its metal yoke (the metal wings the mounting screws go through). Even if you insist on wiring ground, the existing wires must remain connected to the metal box as their first priority, you can't disconnect them from the box to put them on the switch. Try a ground clip. Jan 17 at 21:54
  • @Harper-ReinstateMonica, it is an on/off, and the back of the switch has the UL logo. For the ground, the metal box has two screw terminals at the back for grounding, and at present the ground is connected to only one terminal. I plan on attaching the switch's ground to the second (unused) terminal, and will not be touching the existing ground connection. Thanks!
    – tendim
    Jan 17 at 22:30
  • that's perfect. If you need a ground screw, it's a #10-32 and available at any hardware store. Jan 18 at 3:47
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You're pretty much right on target. Wire nut the two black wires in the box to one black wire from the switch. Check to make sure the switch instructions don't specify "line" and "load" on the wires. One of your black wires in the box is your always hot and the other one is a tap off the hot to another location, probably the always hot on the outlet. The red wire in the box gets wire nutted to the remaining black wire from the switch and then the neutral, white, and grounds get hooked up.

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  • Thanks for confirming; I assumed as much when I read somewhere that the backstab and the screw terminal are "permanently connected".
    – tendim
    Jan 17 at 22:31
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So here's the thing.

Your switch doesn't need to have its ground wired: Since it's a metal box, the switch will pick up ground via its metal yoke and the mounting screws. (note this works for switches, not receptacles).

If your plan is to use a spare ground screw, that's fine.

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  • I think the Kasa smart switches require neutral...(wifi tends to be too much of a pig for any other approach to work) Jan 18 at 4:04
  • @ThreePhaseEel Well the WiFi requirement is momentary so I could see a battery powered WiFi switch which uses the 0.5ma (60mw) for battery top-up. However you're right, I "spaced" the fact that OP's Kasa has a neutral. Jan 18 at 6:07

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