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I have some leftover 12/2 cable and a desire to install an outdoor EV charger at my home. I'm trying to figure out the best way to make this work, without being too expensive. I'm thinking of installing a NEMA 6-20 outlet on the outside of my home, with a single plug, in a weather resistant covering. I should note that the exterior of my home is brick, and I don't fancy putting a new outlet flush by breaking the brick significantly to do so, I'm perfectly happy mounting it on the outside.

Some other information, my home is single story with easy access to the attic, so running the wire there is no problem at all. I plan on going straight up through my garage, running straight through the attic, place a small hole, running through a metal conduit down to the level that I want the outlet to be, and placing the outlet.

Questions that I have for you:

  1. Do I need a weather resistant outlet for this?
  2. Do I need a GFCI outlet if the only thing this will be used for is EV charging? Most EV chargers include GFCI in the device itself.

Anything else I should know about? Thanks for your help!

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    Is the leftover wire wet-rated? Can't do the outside part with NM/B ("romex is a brand name")
    – Ecnerwal
    Oct 10, 2023 at 12:46
  • And how do you get 240V with 12/2? Don't you need 12/3?
    – Huesmann
    Oct 10, 2023 at 12:48
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    @Huesmann nNope. Put in a NEMA 6-20 hot black, hot white, green/bare ground, no neutral.
    – Ecnerwal
    Oct 10, 2023 at 12:50
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    @Ecnerwal Exactly. It needs to be wired to a 240 volt rated circuit breaker, but that's not that big of a deal. No neutral needed for an EV charger. Same applies to any current, if you know you only need 240 V, and not 120V, you can safely wire without a neutral, as long as you use a plug type that is compatible. Oct 10, 2023 at 12:51
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    Oh - and if it is NM/B, you can have hot white (properly marked) at the breaker, but in conduit hot white is forbidden (unless you're sleeving UF, which will waste far more money on oversize conduit than using THWN you have to buy for that part.) Two blacks (or reds or whatever color you like) is just fine for both hots, and the green or bare ground, in the conduit part.
    – Ecnerwal
    Oct 10, 2023 at 12:57

3 Answers 3

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I have some leftover 12/2 wiring

Making the presumption that this leftover 12/2 wiring is NM-B "Romex"™ (yellow jacket on the outside, 2 bits of paper wrapping the black/white/bare on the inside).

place a small hole, running through a metal conduit down to the level that I want the outlet to be, and placing the outlet.

You cannot, in a code-compliant way, run this through conduit on the outside of your house.

Any and all exterior conduit is considered wet at all times and NM-B is not suited for wet locations.


If you happen to have UF-B (grey jacket, much more stiff than the NM-B, no paper inside, grey jacket fully wrapped around each individual wire in the cable), then by all means you can run it through your exterior conduit.

Do be aware of conduit fill rules - you'll need larger conduit than you may think for pulling #12 UF-B through conduit.

You'd be better served to pick up three spools of #12 THHN/THWN wire (which are permissible in wet locations) and running that. Run your left over 12/2 (NM-B or UF-B) to a junction box inside the attic, then tie the wires from the cable to the individual wires and pull those down the conduit. If you use metal conduit you can use the conduit itself as the ground path and get rid of one spool (green) of wire. Since you're running a 240v circuit, both hots can be the same color in conduit, so you can eliminate a second spool of wire.

For details on how to properly join the metal boxes to the metal conduit for electrical continuity and to provide the ground path, please do a search here, I'm quite certain this question has been addressed. If you don't find satisfactory answers, then feel free to ask a new question about that.

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    As long as the conduit goes all the way to the panel. It did not sound like OP was planning conduit the whole way.
    – crip659
    Oct 10, 2023 at 12:58
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    Hots in conduit can be the same color, so no need for 3 spools anyway.
    – Ecnerwal
    Oct 10, 2023 at 13:01
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    Use the tool rental, <s>Luke</s> PearsonArtPhoto - though I am one of those cranks that says the wire through the wall still needs to be wet-rated, even though many inspectors ignore it. But it's truly a trivial cost to buy enough THWN for just the outside run, either way. You can even buy it by the foot if you measure carefully.
    – Ecnerwal
    Oct 10, 2023 at 13:13
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    Pro Tip™: There are no power tools required to make a hole in brick, especially if it's only a 1/2" hole. Frankly, with the proper hand tools, it would probably take less than 5 minutes. Power tools would make it a 30 second job...
    – FreeMan
    Oct 10, 2023 at 13:28
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    I did say "probably", @Ecnerwal... ;)
    – FreeMan
    Oct 10, 2023 at 13:41
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20A good

First, good on you for contemplating a 240V/20A charge rate. We see so many people get hooked into the falsehood that they need a 50A circuit run with 6/3 Romex to a socket etc. etc. Really, 20A is enough for almost everyone.

However, 20A charging creates a problem. None of the manufacturer-supplied "travel units" are capable of 240V/20A charging except the Tesla and BMW units. Now if you're thinking "I found this nice one on Amazon", nope, Amazon now includes Amazon Marketplace (think eBay) and all that stuff is cheap Cheese junk. It's not legal here, your insurer won't pay a claim and your dealer won't honor a warranty repair on the damaged charge port.

Sockets bad

Further, a socket requires a $120+ GFCI circuit breaker, because it's a socket. (regardless of whether an EVSE is involved). The fact that an EVSE contains a pretty good GFCI is moot - it's the socket that needs the GFCI.

I get that "using the travel unit" seems cheap. But when you add that GFCI breaker + socket + junction box + outdoor in-use cover... you're at most of the cost of a wall unit, which needs none of the above. If you actually use a safe/legal UL listed travel unit which supports 20A charging (Volvo, BMW, Tesla with Tesla Tap), you've overshot the cost of a wall unit!

So the best way by far to get 20A is to use a wall unit - almost all can be set using DIP switches to 20A circuit/16A actual charge. Anything from the Grizzl-E to the Tesla Universal Wall Connector. It's a much better experience all around, and porch pirates don't steal hardwired wall units.

The Wallbox also has some marvelous features for solar capture (divert solar production into your EV), load management (can charge an EV at any speed even if the house's electric service is at amp limits), and Power Sharing (charging 2+ EVs off one current allocation). The Emporia can also do that, but needs a WiFi connection to do it.

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    I totally forgot to include a link to "Harper's exposition on EV charging". My apologies! I coulda saved you a ton of typing! :D
    – FreeMan
    Oct 11, 2023 at 11:57
  • I use a 20A 240V EVSE setup. The cord connected EVSE is indoors, and the cord runs outdoors. NEC 2020 210.8(F) was based on a death when a kid jumped on an ungrounded piece of HVAC equipment and died. So new rules were put in place.
    – Bryce
    Oct 27, 2023 at 17:18
  • The 120V travel chargers with nearly every car is actually a 240V unit inside. Some people just modify the plug. California is talking about requiring a dual voltage travel charger be supplied with every new EV.
    – Bryce
    Oct 27, 2023 at 17:38
  • @Bryce Prior to the NEC 2020 code you mention, there was a bit slipped into NEC 2017 that requires GFCI protection for EVSEs specifically. Does not apply to hardwired EVSEs. Modifying the plug is tricky because UL listed ones must have temperature sensors in the plug. Ones with exchangeable dongles have microchips in the plug to sense temperature and also signal socket current rating. Most will tolerate 240V on a 120V plug, but not the later Chevy Bolt units. FYI they're not chargers at all; they just pass the AC straight through. Oct 27, 2023 at 19:10
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  1. The outlet should be protected by an "in use" box - it does not need to be a weather resistant receptacle inside the in-use cover.
  2. Has to be GFCI protected unless you skip the receptacle and install a hardwired charger.
  3. In-use covers are available with many formats, but there's no need to limit the receptacle to a simplex, if using a receptacle.
  4. The hard-wired charger may look less expensive after you price the GFCI dual-pole breaker required by point 1. The fact that it self-resets may spare you an undercharged car one morning, too.

Point 0 stands (when you leave the attic for the outside conduit, which is defined as wet the wiring must be wet-rated.) So you would place a (preferably metal) junction box in the attic, terminate your (probably NM/B) 12/2 cable there, and run the wiring down the wall in conduit. In conduit, white and gray must be neutral and can only be neutral. If you use metallic conduit such as EMT, by connecting it to the properly grounded metal junction box you only need two hot wires to your outside box, and those can be a single color (that's any color not white, gray, or green) of THWN or other wet rated wire. Or you can run a ground wire (bare or green) in the conduit if the conduit is non-conductive.

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