I currently have a 12A EVSE that takes either 120V or 240V and uses a normal three-prong (NEMA 5-15) plug. I am looking to install a 240V outlet on a 50A circuit breaker to use with this EVSE, but I'm wondering which receptacle to use with this new outlet. I've ruled out a NEMA 5-15/5-20 receptacle, so I will need an adapter to use my current EVSE for any outlet I install. Would it make more sense to install a 14-50R receptacle, a 6-50 receptacle, or some other type?

  • 2
    What make and model is your EV, and what sort of chargers can you get for it? Sep 13 '19 at 0:43

NEMA 6-15 and you're done

Outlets aren't that expensive. Simply fit the correct one.

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The third one.

If your wiring is 12 AWG or larger copper and your breaker is 20A, you can fit a NEMA 6-20 instead.

Now, noting this thing is dual voltage, the right way to deal with that is have it have a removable inlet (the way a PC does) that takes an IEC connector. Then you simply change the cord to what you're plugging into. However you can make a NEMA 5-15R to 6-15P cheater cord if you really want to. If someone finds a 6" long cord with a funny plug on it, that's a big fat hint to be careful what they plug in.

If you are thinking of wiring up a universal future adapter socket, you can't. What you can do is run 6/3 cable (or #8 THHN in conduit) to a large 4-11/16" square junction box. The large 4-11/16" square box gives you the room for big wires and splices. At this point you can install any of these pairs:

  • NEMA 6-15 receptacle with a 15A or 20A breaker
  • NEMA 6-20 receptacle with a 20A breaker
  • NEMA 6-30 or 14-30 with a 30A breaker
  • NEMA 6-50 or 14-50 with a 50A breaker

Note that except for a 15A receptacle on a 20A breaker, the receptacle size must always match the breaker size. And of course you can't exceed wire maximums.

  • Thanks! Why would you recommend installing a 6-20 and adapting to 5-15/5-20, rather than installing a 14-50 and adapting to 5-15/5-20?
    – palswim
    Sep 13 '19 at 4:25
  • 1
    Yes, for many reasons. A 14-50 is not an option unless you install much larger wires and a 50A breaker. (Breakers MUST match receptacles amp ratings except a 15A receptacle is allowed on a 20A breaker only). Even then, it would fail to protect the 15A device. Sep 13 '19 at 4:41
  • Ah, I mentioned the 14-50 and 6-50 receptacles in the question, but I updated the question to make it explicit that I will install on a 50A circuit.
    – palswim
    Sep 13 '19 at 5:07
  • @palswim OK, then you'd just need to change the breaker to match the receptacle. The smallest receptacles and breakers may not be willing to talk to a #6 or #8 wire, so you'd have to pigtail that. Sep 13 '19 at 5:11

Eventually, I decided to wire the outlet as a NEMA 14-50 (hot-hot-neutral-ground) rather than a NEMA 6-50 (hot-hot-ground) because the I can re-wire to a 6-50 easily enough by capping the neutral wire and from my limited research, I found that more EVSE chargers used NEMA 14-50 rather than NEMA 6-50.

As far as adapting the outlet to my current charger, creating a NEMA 14-50 to a NEMA 5-20 homemade extension cord (cheater cable, as one helpful answer named it) did not pose too much difficulty.

My EVSE (E346031) only draws 12A. A short would trip a 20A breaker or a 50A breaker, so I had no fear about overheating and the extension cord. For any other EVSE, I would probably have to create a different extension cord.

  • 1
    I find it odd that EVSE chargers use 14-50s since they have no use whatsoever for neutral.... Sep 24 '19 at 23:54
  • Be aware that a 14-50 to 5-20 cheater cord is not to code, because (1) an appliance cord designed to plug into a 5-20 outlet need only be capable of sustaining 20 amps before melting or catching fire, and (2) your breaker will only pop over 50 amps, which leaves plenty of room for a cable-melting fire-starting fault to occur. It's not common to see a fault draw 40 amps without being a dead short, but it is possible, and such a fault would almost surely burn down your house, so be careful and never leave a cheater cord unattended in use. Sep 26 '19 at 18:04
  • (Incidentally, you CAN adapt 14-50 to 5-20 in a way that IS to code, by getting an adapter that has an appropriate 20A fuse or breaker in it. Although I can't find one, and I can find LOTS of the not-to-code kind. Home Depot even seems to sell them, which confuses me.) Sep 26 '19 at 18:10
  • "A short would trip a 20A breaker or a 50A breaker" FALSE. The trip curves are quite different, and there's a big "fail zone" in there where you are totally unprotected. Frankly, depending on the wire size and length, the wires resistance may be high enough to preclude any possibility of an instant-trip on a 50A breaker. So it would just sit there and burn until the thermal trip eventually popped, which might be "never" if it's drawing <67A. This is bad advice and a Code violation. Dec 3 at 20:56

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