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I am trying to add an outlet connecting to a three way light switch. Within the box there are three bundles of wire. Two of them are black, white and ground and the other one is black, red and ground. The first two blacks are bundle together with a pigtail to the light switch. The two whites are bundle with pigtail to the light switch. The red wire is connected to the light switch but the black wire is not connected to anything. How should I wire the outlet so that it's always on?

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The ones stick out are the wires going to new outlet

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  • You might want to check your local code, in my area that is not allowed because a dimmer could be installed inplace of a switch or so I was lead to believe. You might find out where the other ends of the wire are and how they are connected.
    – Gil
    Jul 1 '21 at 19:25
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    Can you provide a picture of the inside of the switch box?
    – JACK
    Jul 1 '21 at 19:49
  • My hunch is that (a) the black/red is really black/red/white and you are missing a wire somewhere and that (b) black used to be one of two travelers but that now you have smart switches that only need one traveler. So: picture of the wires showing how they connect to each other and to the switch and make/model of the existing switches (which will help confirm the details). Jul 1 '21 at 20:33
  • Yes you are right. It's black red and white. I figured out that the red is always on, so I could just connect my black wire for the outlet to that on the light switch. And yes it is a smart switch, so you are right on. Jul 1 '21 at 21:12
  • That red is a traveler between the switches. Don't use it for this. I'll write up an answer later. Jul 1 '21 at 21:33
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You've got 3 cables (grounds are ignored in this explanation and should all be connected together and to the new receptacle):

  • Incoming power - Black/White
  • Ongoing power (to another light or receptacle) - Black/White
  • 2nd Switch - Black/Red/White

The confusing part is that the Black of the switch cable is not currently used. That's because traditional 3-way switches need 3 wires - two travelers plus either hot or switched hot - but you now have smart switches (likely not there originally) which only use one traveler and use that traveler as the hot wire as well.

There are some more complications - e.g., how is neutral getting to the fixture. But since everything else is working, adding a receptacle at this location should be very straightforward. (Adding a receptacle at the other switch would be more complicated). You don't even need to figure out which cable is incoming power!

Wire up the new receptacle as follows:

  • Hot = Add to the existing black bundle.
  • Neutral = Add to the existing white bundle.
  • Ground = Add to the existing grounds.

Depending on what wire nuts were used and what condition they are in, replacing with new appropriately sized wire nuts (each color can handle different numbers of each size of wire) may be a good idea.

Don't connect to the Red - even though that happens to be hot right now, because (a) you need to match your hot & neutral wires to the same cable and (b) if the 3-way switches are ever switched (pun intended) back to regular switches then that red wire will become a true traveler again - only on 1/2 the time.

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  • I tried as you suggested, but there's only power to the outlet if the lights are on. the only way to have power all time to the outlet is connecting it to the red. What do you think? For some reason neither of the black wires going into the box are always supplied with power. If the red is just the traveler, shouldn't it be off at some point when switching the lights on and off with both switches? Jul 2 '21 at 3:40
  • There is another possibility of how this is all wired, but it seems less likely. Pictures of this switch box (showing all the wires you described) and of the other switch box (the other 3-way switch) would be really, really helpful. Jul 2 '21 at 4:06

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