Can I put a GFCI outlet on a 3-way switched feed to a garage?

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.

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* 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.