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Here's the situation: House was built in the 1980s. My laundry room has an existing NEMA 10-30 outlet that is not being used since we have a gas dryer. I am thinking about getting an electric car so I'll need a place to charge it in the garage which is located just outside the laundry room door which is just adjacent to this unused 10-30 outlet. My thought was maybe I could junction off of this outlet and run a 10 gauge Romex to the garage wall for a new outlet to plug in the car.

I was hoping to not have to run all new cable from the breaker box because that is in the basement. The breaker for this circuit a 2-pole 30 amp breaker. Since I may some day want to use this laundry room outlet if we were to get an electric dryer, I was thinking it would be nice to keep that installed as an outlet and just run new wires from that to the garage. I wasn't sure if that was acceptable and if I did this would it mean that I'd only be able to use one outlet at a time. The car can be set to pull 24 amps for the 30 amp circuit. (80% of 30 amps) As I said I don't need the outlet now but if some day I wanted to use it would this be a problem for the circuit?

My other thought is to just move the NEMA 10-30 outlet (or install a new NEMA 14-30) to the garage and use the existing outlet box as a junction box to tie-in the new cables. Then close the laundry room box up with a blank faceplate so it won't be usable anymore. I would then use the newly installed garage outlet for the car charging.

I appreciate any advice you can offer for this situation. I've relocated 120 volt outlets before for various reasons but I've never done this for a 240 so I wasn't sure if that makes a difference. I'll likely get an electrician to do the work either way but just thought I'd get some advice here on what is possible.

Thanks for the responses this has been helpful. I was not aware that the code requires EV chargers to be on a dedicated circuit so that was good to learn. Here's a few pictures I was finally able to take of the outlet wiring. I'll probably just get an electrician to add a dedicated 50 amp circuit to the garage instead and leave this one as is.

WiringOutlet wiring10-30 outlet

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  • It's very likely possible to convert your current dryer outlet into an electric car charger outlet, but you can't have both -- current code requires electric car chargers to be on a dedicated circuit. See @ThreePhaseEel's answer in the question I linked for the exact code cite. – Nate S. Oct 22 '19 at 23:00
  • Can you post photos of the inside of the dryer receptacle box please? – ThreePhaseEel Oct 23 '19 at 1:25
  • Also, are you sure your electric car charger needs a NEMA 14-30? Most are 208-240V/50-60Hz, single phase, and thus do not need the neutral at all! – ThreePhaseEel Oct 23 '19 at 1:27
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The good news: you have the wires you need

The good news in your situation is that you have all four wires (two hots, a neutral, and a ground) present already (which makes me wonder why the NEMA 10 receptacle was installed in the first place, but I digress). This means that this circuit can safely power a 16A EVSE with ease.

The bad news: electric car chargers can't share

The bad news is that as per NEC 625.40, electric car chargers (EVSE) require a dedicated circuit:

625.40 Electric Vehicle Branch Circuit. Each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.

While this means that the circuit won't be usable for a dryer any longer, it still leaves you with two options: either you can convert the existing run into a feeder using a small "spa box" sized subpanel (and replace the dryer receptacle with a NEMA 14-30 while you're at it), or you can remove this receptacle and use the box as a splice point to start your new run of 10/3 to the garage.

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You need to see if there's a ground inside the box

For your application, equipment safety ground MUST be separate from neutral. let's examine the cases.

There is neutral and a ground wire (or metal conduit)

The NEMA 10 does not connect to this ground. You can extend off this outlet by tapping the two hots and ground (and neutral if your charger needs it). Smash the NEMA 10 socket. Cover it with a blanking plate; you can normally have multiple 30A sockets, but not with EVSEs.

There is a bare stranded neutral woven around the other wires

This is the only kind of cable that was ever allowed to use a bare neutral. You can go one of two ways here.

  • Re-designate that bare wire as a ground wire, and you will be permanently unable to ever use that cable to power any electric dryer. This can ONLY power a NEMA 6 socket.
  • Keep that wire as neutral, which is grandfathered, and retrofit a ground wire. Make sure they don't touch!

3-wire cable, but the neutral is bare

This cable was illegal to feed a NEMA 10 at the time it was installed, and therefore is ineligible for grandfathering. Because the bare wire is illegal to use as neutral. It must be re-tasked to be ground, and can never supply a dryer, only a NEMA 6.

3-wire cable, white neutral (or braided bare neutral as mentioned earlier)

You cannot tap this. Period. End of subject. It is a shame, if you woke up one day and found that previously a ground had been retrofitted, then you could have tapped it. But no luck. Sorry!

If you think you can retrofit a ground and immediately tap it, in one step, no... But my suggestion is "sleep on it" :)

Retrofitting Ground

A separate ground wire can be retrofitted. It can run on its own route. It only needs to reach any of the following:

  • the service panel this circuit is powered out of, obviously
  • any junction box with an all-metal-conduit path back to the service panel
  • any junction box with a #10 or larger ground wire back to the service panel, such as a water heater or air conditioner.
  • any part of the Grounding Electrode System, those copper wires that come out of the panel to go to water pipes or ground rods.

Change the dryer receptacle to NEMA 14-30 at this point for plausible deniability that the ground retrofit was unrelated work. You must leave the 14-30 disconnected because you can't have other outlets on an EVSE circuit.

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(I updated your use of 110/220 volts because that hasn't been widely available since the 1960s.)

The answer is no. NEC does not allow multiple outlets on a 240 volt circuit. Anyway, wouldn't you rather a 50 amp 240 volt circuit for charging your vehicle?

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