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I'm running 14/3 UF cable from my house to my garage. I start with a two wire source to a 3-way switch to a 3-way switch in the garage to a few lights. Can I put a GFCI receptacle on the outside of the house between the 3-way switches? if I run 14/3 will that give me the extra wire I need?

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    Any reason you can't put the GFCI upstream of the switches (or on a breaker, or after the switches)? This seems like needless complexity.
    – isherwood
    Nov 10, 2022 at 15:23
  • If you haven't buried the cable yet, take look at running conduit instead for future upgradability. Bonus points if you oversize the conduit large enough that a future owner can easily run cable for EV charging - I've heard that can bump the house's resale value a bit.
    – maples
    Nov 10, 2022 at 17:37
  • Do you want the GFCI receptacle to be controlled by the two switches? Or always on? I don't know what you mean by "between the switches". The cable to the receptacle will be connected in a junction box, presumably at one of the switches. Usually one of the boxes will have an always-on wire, and the other one will have a source of switched power available. If you add a junction box in between, you have power that is controlled by one of the switches but not the other one, and it will be randomly out of sync with the lights.
    – jay613
    Nov 10, 2022 at 17:41
  • Can I put a GFCI outlet on a 3-way switched feed to a garage? Sure, as long as it's next the switch with the incoming power and the neutral is present.
    – Mazura
    Nov 11, 2022 at 6:13

3 Answers 3

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No, you cannot put a receptacle on a 3-way cable (14/3) which consists of ground, neutral, and two travelers - there is no "hot" in this cable.

To add a receptacle where you want it, run a proper 14/2 cable out to it.

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A /3 cable running between 3-way switches carries two travelers and one other wire. In your case, that extra wire is neutral. You need to either use a /4 cable and include hot, or use a separate /2 cable with hot and neutral for the receptacle(s).

As far as where to put the GFCI (no matter how you get there), I highly recommend putting a GFCI/receptacle inside the garage and then use the LOAD connection to wire up an ordinary receptacle (weather resistant, with an in-use cover, but not GFCI) outside. That will protect the GFCI from rain and help it last longer, while still keeping the GFCI reset location nearby.

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  • I know what you intended, but saying " wire up an ordinary receptacle (weather resistant, with an in-use cover, but not GFCI) outside. ..." risks them connecting it upstream from the GFCI. You said " ... use the LOAD connection ..." So it should be very clear already, but my "things can go wrong" engineers brain suggests adding eg " so that the outside socket is protected by the GFCI...". You may (undwerstandably) consider that's overkill. (I'm 71. I'm still alive. I look for traps.) Nov 11, 2022 at 9:13
  • Just an FYI, The /4 solution will work with a standard 3-way, but not with a smart switch that needs to use a neutral to power the switch. I ran into this exact same problem where the original 3-ways worked fine, but as soon as I replaced with smart switches, it kept tripping the GFCI between the switches. In this case I think the best solution would be to use the separate /2 cable.
    – Travis
    Nov 11, 2022 at 12:58
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Your question is how to deliver 3-way control and receptacle power on a single 14/3.

Only way I know is Smart Switches. But that's powerful.

You will have two choices of how to wire it, depending on the product selection you use.

First, a smart switch master in the garage - take care to select one that has a partner "smart switch remote" that has the control features you want at the house. Now the wires in the 14/3 will be:

  • Black = always-hot
  • White = neutral
  • Red = datacomm signal line between the switches (if needed; otherwise free. Feel free to make this an MWBC if it's not otherwise used, which will give you Perfectly Respectable Level 2 EV charging in the garage.)

Alternately, a smart switch master at the house, and at the garage a smart-switch remote that communicates wirelessly or via powerline signaling. This remote can tap always-hot and neutral for its own power; it just won't have any spare data wires. Here, the wires are assigned:

  • Black = always-hot
  • White = neutral
  • Red = switched-hot to the light (which goes right past the remote in the garage, not interacting with it at all).

With either wiring scheme, the circuit can be tapped anywhere to power anything - receptacles, smart switch remotes, you name it. In the second case, switched-hot is available so additional lights could be hung off that which will respond to the switch.




* How do you get Level 2 EV charging out of this? By using the first trick with a wireless-communicating smart switch, giving a spare red. Then, wire it as a MWBC. MWBCs are allowed to have both 120V and 240V outlets on them, so you stick a NEMA 6-15 general purpose receptacle on it.

Then you plug in an EVSE built or configured for a 15A circuit (which means 12A actual given to the EV). This will deliver 2.9 kW to your EV, or 75-90 miles in a 10-hour charge session. (more if longer). If you need more in a single day, you can catch up over several days. If even that is not enough, DC fast charging is REALLY fast.

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  • Interesting answer to a different question, I think... It should also mention that if you're going to use a hot/hot/neutral/ground cable to supply both 240V and each leg separately, the two opposing-phase hots MUST come from a linked pair of breakers since otherwise in some failure modes you may exceed the rating of the wiring. I'm also going to quibble with "must" here. This is an interesting solution; it is certainly not the only solution, even for the question you are actually answering.
    – keshlam
    Nov 10, 2022 at 19:41
  • @keshlam well, I have been known to do that lol... I thought the question was crystal clear and I added language restating it. Don't be that guy who disclaimers must be written for lol. That is only one of several MWBC safety requirements; rather than write a book LOL, I gloss over MWBCs and send you to a link. What's wrong with that? As for "must", that's a bold claim. Bold claims need bold proofs. The answer box beckons! No fair using ground for neutral :) Nov 11, 2022 at 1:45
  • The edit helps clarify your intent; thank you. Let me reread and see if I want to retract my grumble
    – keshlam
    Nov 11, 2022 at 2:21
  • "But that's powerful." ???
    – Mazura
    Nov 11, 2022 at 6:16
  • @Mazura lets you turn a 3-way circuit into 3-way + 120V outlet + level 2 EV charging, so yeah. Nov 11, 2022 at 6:38

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