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I have a question with regard to installing a NEMA 14-50 for EV charging. I know these outlets are not fantastic for this purpose, but I’m looking to install one just temporarily to be replaced by a hardwired or plugged dedicated wall unit.

My family bought an older house recently, which has been remarkably well maintained. I have a 40A non-GFCI breaker in my 200A panel in the basement, which was intended for an oven (in the basement? I know, right?).

To accommodate that connection the previous owners put in 3/4” RMC with three (I think) 8 gauge copper wires (may actually be 6, haven’t measured them) and one thinner (aluminium?) wire hooked up to a 14-30R over a distance between 60 to 70ft.

I’ve unhooked that receptacle to repurpose the wiring and hook up a NEMA 14-50 receptacle on the outside of my house. The RMC is still entirely inside the house structure. I sealed off the hole with duct seal, caulked the receptacle—-pretty sure no moisture will get in. They’re real stiff wires to work with, encased in rubber and then paper-like wrapping, both in excellent condition: one white, one black and one red. White is obviously neutral, and the other two L1 and L2.

My question: there’s a thinner (I suspect) aluminium wire in that same RMC, which I’m pretty sure is to ground the receptacle (I have seen it elsewhere in the house). Can I just use that same wire to ground the socket itself? As in, run a piece of wire from the socket under the green ground screw to the screw in my receptacle to hook up the socket to the same ground?

I have seen plenty of folks ask about hooking these things up, but haven’t yet found anyone discuss the thin aluminium wire (it’s not plated copper).

I can add a photo if that’s useful. FYI: I do have experience with this kind of thing abroad, just not with slightly older cable in the US on the east coast.

Thanks y’all!

Martin Uildriks
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You can ignore the wire or land it on a ground screw in the box, then ground the receptacle to the box

Since you have a continuous run of RMC from the panel to the outlet, that's your equipment grounding conductor, and the extra aluminum? wire is superfluous. Do what you will with the extra wire, and simply use a 10AWG copper pigtail to ground the receptacle to the box, presuming that you're using a metal box that is.

Since you have conduit, if you don't mind redoing the run...

Since that run in conduit, if your panel is listed and labeled for Eaton BR breakers and has 2 extra spaces in it, then you could replace the thin aluminum wire and one of the copper wires with a 18/2 tray cable, then install an Eaton EVCI into the panel and a junction box kit at the outdoor location. This gives you a J1772 cable coming out of the wallbox without the need for extra parts, as all the EV charging smarts are in the branch circuit breaker itself.

ThreePhaseEel
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