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While looking into EV charging I noticed I had a 240V receptacle (Leviton 10-50R) conveniently located right beneath my main panel. After some research (I have little to no electrical knowledge), I found out that not only is the 10-50 no longer used, the wiring for mine is apparently "cheating", using black-white with ground wire instead of black-red with neutral.

However this works out for me since I can just convert this to a 6-50 receptacle, which is what I need for EV charging (hot-hot-ground). I also apparently need to install a new breaker because the 240V one for this is rated at 20 amps for some reason...

So, a few questions:

  1. Is the existing wiring good to handle EV loads (32 amps over several hours)?
  2. Is it safe/good idea for me to DIY the breaker and receptacle? The most I've done is wire a new light fixture...

enter image description here

user96104
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    Those wires look too thin for 50 amps. You need at least 6 gauge for 50 amps and 10 gauge for 30 amps. I would be surprised if they are even 10 gauge. Check the breaker size first, then the wire gauge, then get the 6-50. – crip659 Jul 24 '23 at 21:14
  • What breaker is it connected to? Any labeling on the cable sheath? If it is "right beneath my main panel" then all of this is irrelevant anyway because you could just run a new cable of the appropriate size (or individual wires in conduit - that is often done if truly "right beneath the panel"). But bigger question is **Why use a receptacle at all?** For a bunch of reasons, hardwiring EVSE is almost always better than plug/cord/receptacle, particularly with the latest version of the NEC due to GFCI requirements. And finally, have you done a load calculation to see how much EVSE you can add? – manassehkatz-Moving 2 Codidact Jul 24 '23 at 21:14
  • First off, your assumption that white can't carry current is wrong. On a 240V circuit it's not weird to use wire this way, since black+red NM cable doesn't exist. They should have marked the wire, but that's minor. There also will no doubt be a full answer soon - but for now I'm adding to the chorus saying this is not 50 amp wire. That looks like 12 awg, i.e. 20 amp wire. All is not lost though! A 16A hardwired EVSE on a 20A circuit can be a *great* option for people who drive reasonable or even reasonable-ish distances each day. You won't even have to change the breaker in the panel. – KMJ Jul 24 '23 at 21:37
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    @manassehkatz-Moving2Codidact they said it's on a 20A breaker at the end of the second paragraph. If that's 12 AWG wire you could throw a hardwired 16A (or 16A configurable) EVSE on it in place of the outlet as-is, since no GFCI would be needed. – KMJ Jul 24 '23 at 21:43
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    @KMJ I think OP added the breaker size later, or I totally missed it before. The money is on the second choice. – crip659 Jul 24 '23 at 21:46
  • @KMJ crip659 is right. I checked the edit history - the 20A line was not in the original – manassehkatz-Moving 2 Codidact Jul 24 '23 at 21:53
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    That explains it, since it was there when I looked. – KMJ Jul 24 '23 at 22:30

1 Answers1

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First, 32A is optional and perhaps unwise.

That's just a default choice handed to you by the manufacturer, by way of giving you a "travel unit" EVSE with the appropriate plug to charge at RV parks (the 50A RV receptacle, often used for 40A ranges).

Cars can actually charge at any rate from 6A to the hardware limit of your car - the car follows a signal from the EVSE ("charger") that tells it the safe amps to draw. The carmaker just didn't toss in gratis the necessary kit to do it. But some automakers will sell you the correct "dongle plug" for any ampacity of charging for not much at all. Or you can use another model of EVSE.

If you're going with a wall unit EVSE, the charge rate is a DIP switch setting.

32A is intended for travel where you need a complete charge overnight, and they give you the RV plug because it's found in RV parks. For daily driving it is overkill, and it's also too much for most house's electrical systems.

Anytime you add a load, you must do a NEC Article 220 Load Calculation e.g. NEC 220.82 alternate method. Whatever headroom remains in the Load Calc, you can charge the car at 80% of that (actual) or 100% of that (breaker).

The vast majority of people can actually get it done on a 240V/20A circuit! (Reddit veteran opening up on the "Giant Charger" crowd). That's 3.8 kW of actual charging, and if you're spending less than 2 hours a day commuting, it'll probably be plenty. It's worth a shot because it's practically free, given the existing stuff in your house.

That socket...

You can't just put a bigger breaker on any random wire. That breaker is 20A for a reason -- that wire is either 20A wire. The breaker protects the wire.

Actually, I'm not confident that it is 20A -- you'll need to find a bit of the sheath that is exposed and see if it says "12 AWG" or "AWG 12" - otherwise it is 14 AWG and that can only take a 15A breaker. One way to find out is get a cheapie 15A receptacle and see if the wire will fit in the backstab hole. If it won't fit, it's 12 AWG wire and you're good to 20A. So you can simply leave the breaker alone.

If it's 15A wire, you'll need to change that breaker to 15A, and I don't think we can dodge the GFCI requirement at that point. Check your state's amendments to NEC 2020 to see if they deleted the requirement.

Installing a new outlet under NEC 2020 will require GFCI protection at the outlet in most locations. However, I would argue this is an incorrect outlet and therefore, replacing it with a NEMA 6-20 is a repair :) which would not invoke the GFCI requirement. EVSEs contain smart GFCIs anyway.

enter image description here

The one on the right.

Install a steel junction box - I would go with a 4x4 steel box with a domed cover.

To get a 20A EVSE

If you are willing to get a wall-mount EVSE and hard-wire it, this is easy. Most of them have DIP switch settings to set the breaker size - make sure your choice does. Though I would be reluctant to buy a non-Tesla wall unit, since the whole industry just changed horses midstream and model year 2025 and on cars will be using the Tesla NACS connector.

If you are using the provided "travel EVSE", contact your manufacturer to see whether they make a NEMA 6-20 dongle for that EVSE. If it's Tesla, they definitely do, and it's $35.

You can also buy inexpensive "travel EVSE's" online - make sure it is UL listed.

Now, this isn't really code legal, but you can use a short cheater cord (NEMA 5-15R on one end, 6-15R on the other end) to plug the provided 120V/15A plug into 240V. Only do this with EVSEs - they are voltage-blind, and will still tell your car to draw 12A - and the car will figure out it's 240V. This will result in better than twice level 1 charging speed.

Harper - Reinstate Monica
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