Future proofing for 240V outlet

Question

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?

Answer 1

EV charging is special. The EV can actually "dial the amps" to whatever the circuit can handle, but something must tell it what the amp limit is. That is what EVSE's do.

When I originally wrote this, I did not realize OP had a portable EVSE with a variety of adapter plugs.

Those adapter plugs are special; they have a 4th pin on the EVSE side which tells the EVSE the ampacity of the socket. (which the EVSE tells the car). Using hinky adapters will cause the car to draw the wrong current, causing problems like nuisance trips or fire-based detection of Zinsco and Challenger breakers lol. When using these portable EVSEs, the ampacity of the circuit MUST actually match the socket type.

That said, it's perfectly fine to "fool" the EVSE with regards to voltage only, which is what this discusses with OP. But really, the right thing to do is get the right connector end. But let's say you have a 120V/30A TT30 socket, and they don't make one of those. It's OK to "cheater" the 10-30 or 14-30 plug to fit onto a TT30. That will tell the car "30A" (correct) and surprise, the voltage is only 120V - but the car knows what to do with that.

End edit/preface. Other edits in the log.

NEMA 6-15 and you're done

Outlets aren't that expensive and neither are plain breakers. Simply fit the correct one. And the correct 15A or 20A breaker per NEC 210.21.

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.

Answer 2

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. Editor's note: This is a Code violation and creates significant danger, as the 50A breaker will not trip when needed to protect a 20A device. UL listed adapters are made, which have internal 20A fuses to solve that problem, or a homemade one could be built with a fuse.

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. Editor's note: No, it would not trip a 50A breaker. That's the problem! This also doesn't address time-to-trip in an inverse-time overload condition; a 50A breaker would trip far too late.