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I am looking to add a 30A outlet in my garage for the purpose of charging an EV. My home has 200A service coming through the main panel, and currently there are no sub-panels except one for the central air AC unit.

My dryer is located on the other side of the garage wall where I would like to place the outlet. When we bought the home, the previous owner had tapped into the dryer outlet and added a 240V outlet where I would like this one. This was not up to code, so we had them remove the outlet and plate over the box before we closed.

Fast forward a few years and I'd like to put an outlet here but do it right. I do NOT want to install a dedicated charger, but would rather install a 14-30 outlet that most any non-hardwired car charger can use, both for my current use and future-proofing.

I opened the box where the previous outlet was and found 10/3 wire w/ground (picture below), even though the dryer outlet on the other side of the wall and the one we had removed are both 10-30 receptacles, and so ungrounded (home was built in '92). Testing these wires confirmed two hots at 120V each, one neutral and a dead ground. Odd thing is, the bare copper wire which should be the ground wire is wired as neutral, and the white neutral wire is dead. A no-contact voltage tester indicates the bare copper has live but low voltage present. With a DMM, I get 120V from either hot to this wire, and nothing from either hot to what I thought should be the neutral. Is this normal, or am I doing it wrong?

I was NOT planning to just add a receptacle back where it used to be, tapped off the dryer. My plan is to add a 60Amp breaker at the main panel (about 25 feet away) and run 6ga wire to a subpanel in the garage, and within that panel add two 30A breakers, one to feed the dryer (with a proper 14-30 outlet) and one to feed the EV outlet (also 14-30), feeding both with 10/3 romex. I consulted an electrician about this and he said I only need a 50A breaker in the main panel for this setup(???). I may, MAY, elect to add a 14-50 outlet instead of the 14-30 for the EV outlet in the garage, in which case I'd upgrade that respective breaker and wiring as well as bump the 60A breaker to feed the sub up to 80. I'd cap off the existing run to the dryer, and yank out the wires the previous homeowner ran to the aforementioned garage outlet. I plan to do all this work myself, with the exception of the work at the main panel. I will hire an electrician (a different one) for that after I've wired everything else up.

I get that I could leave the current dryer setup alone and just add a receptacle on a dedicated circuit for the EV charging, but after seeing inside the box for the receptacle we removed I'm growing increasingly uncomfortable with how the dryer line was tapped, and I figure I'll just go ahead and update that to 14-30, and try to do it right. Does all this sound reasonable? I would greatly appreciate any input, insights, or comments. wiring for removed receptacle

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    Was there any protection on those cut wire ends when you opened the box up? Having bare wire like that with no protection, I'd think would be a safety hazard, even if nothing were connected to them. I'd at least put wire nuts on them for protection. Also, it looks like when they took out the previous outlet that was there, they just cut the wires, and didn't do you any favors doing that by cutting them so short. There's probably not enough wire length in there to even make pigtail connections, as I believe code typically says that one needs a minimum of 6" of wire in the box.
    – Milwrdfan
    Jan 21 at 4:53
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    "With a DMM, I get 120V from either hot to this wire, and nothing from either hot to what I thought should be the neutral. Is this normal, or am I doing it wrong?" No, you're not doing it wrong - this is why 10-30 outlets are dangerous and illegal now. Also why tapping it to feed a 14-30 is equally dangerous and illegal.
    – J...
    Jan 21 at 14:02
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    @Milwrdfan; Totally agree with your comments and no, there was no protection on these wires. When i pulled the faceplate off this is exactly how it looked. i know, very dangerous. i have yet to pull the faceplate off the dryer receptacle on the other side of the wall but I already know I'm going to cringe when I see how he tapped the line. that's why i plan to just yank all this out and run new wire for the dryer too, upgrading the receptacle/circuit in the meantime.
    – KM001
    Jan 21 at 16:46

3 Answers 3

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I opened the box where the previous outlet was and found 10/3 wire w/ground (picture below), even though the dryer outlet on the other side of the wall and the one we had removed are both 10-30 receptacles, and so ungrounded (home was built in '92). Testing these wires confirmed two hots at 120V each, one neutral and a dead ground. Odd thing is, the bare copper wire which should be the ground wire is wired as neutral, and the white neutral wire is dead.

Yes, that's just the kind of horky nonsense we see anytime NEMA 10 is involved. In fact it's a bit of a surprise to find a groundless NEMA 10 in 1992, since groundless #10 wires were all but gone from the market. Some people installed 10/2 w/ground, and abused the ground as neutral; but that has always been forbidden (and thus, NOT grandfathered). Once old stocks of 10/3 "without ground" ran out, you were to use 10/3 with ground and simply not connect the ground if using a NEMA 10-30.

However, one thing was legal: having multiple outlets on a 30A circuit.

I was NOT planning to just add a receptacle back where it used to be, tapped off the dryer. My plan is to add a 60Amp breaker at the main panel (about 25 feet away) and run 6ga wire to a subpanel in the garage, and within that panel add two 30A breakers, one to feed the dryer (with a proper 14-30 outlet) and one to feed the EV outlet (also 14-30), feeding both with 10/3 romex

Well, 6/3 Romex (NM or UF) is only good to 55A, but I wouldn't use it anyway. They don't make that breaker size, so you're free to either "round down" or "round up". Code requires that you provision a subpanel feeder "sufficient for the load to be served", so you couldn't plan to use more than 55A. The EV charging requires a 125% derate on the maximum current the EVSE will authorize, so 24A max programmed charge rate requires 30A provisioning, 30A wire and 30A breaker. So you would be counting on the dryer being <25A actual.

I wouldn't use it because you can get more suitable feeder for <1/2 the price, as manassehkatz discusses. #2AL feeder is about the price of 10/3 Romex. Large feeders work best as aluminum - long history has proven its reliability and economy (and the lugs you'll be attaching to will be aluminum). Part of its secret to success is electricians have always used torque wrenches to set large lugs. As far as stiffness, AL is about the stiffness of the next size smaller copper (so akin to #4 Cu).

90A will cover present and future EV charging to 60A+ your dryer simultaneously, and if you can avoid simultaneous dryer use (or certain tech solutions were are expecting soon), you can run 80 or 90A shared between two EVSE's, which is pretty much the "state of the art" for EV charging.

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  • EV chargers with inputs for connecting current transformers have been a thing over here in the UK for a while, I'm kind of suprised you don't have them in north america yet. Jan 26 at 23:39
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The old wiring is 100% irrelevant to this, since you know it isn't large enough for anything more than 30A. So ignore all that and the plastic box, etc. Except that you should replace the existing 30A dryer 10-30 receptacle with a 14-30 receptacle, which will be easy since the new subpanel will have ground going back to the main panel. You will need to change the dryer cord and remove the neutral/ground bond on the dryer.

Back to the main issue: subpanel. That is the right way to do it. Better than 6 AWG copper is 2 AWG aluminum, which should get you all the way up to 90A! You don't have to install a 90A feed breaker - any size large enough for what you plan to use in the subpanel is fine, but no larger than 90A. You can always change it later.

I am fairly certain that the subpanel is not required to have a main breaker. If it were in a separate building then a shutoff would be required, which a main breaker would satisfy. But a main breaker for convenience when working on the panel is just fine if you want to have one. If you have a main breaker in the subpanel, any size >= the feed breaker size is fine. You can have a 100A breaker with a 60A feed.

You probably don't need a huge subpanel, but you should always get larger than you think you need. You should certainly have enough for:

  • 2 EV chargers (Tesla + Ford, based on comments to another answer) - 240V
  • Dryer - 240V
  • 1 receptacle circuit - 120V
  • 1 lighting circuit - 120V

which is 8 spaces. But bigger is better. Maybe someday you'll want to build a shop (240V tools) or do other things with the space. Also keep in mind that many circuits, especially in garages, require AFCI and/or GFCI, and those won't work in 1/2-size spaces. If a panel says 20 spaces/40 circuits, treat it as 20 spaces/20 circuits.

As a semi-random example from Home Depot (your local pricing at various sources will vary, of course), there is a Square D Homeline panel currently selling for < $100, in stock in at least some locations (i.e., not some "can't find it anywhere due to supply shortages" thing) with 24 spaces ("48 circuits" - ignore that), 3 x 20A single pole breakers, 2 x 30A double pole breakers (one of those will be for your dryer). You'll need to add more breakers, and you may need a ground bar (not sure, haven't checked the specs in detail) because this is being installed as a subpanel. But compared to everything else (particularly the cost of 25' of 6 AWG copper, though hopefully you'll be able to switch to cheaper aluminum) this is "nothing" and provides lots of room for the future. Also keep in mind that the biggest drawback to any subpanel (instead of individual receptacles going back to the main) is making sure you have code-required workspace in front of it. But that will be the same for any panel, so might as well go big.

Don't worry about aluminum. The problems with aluminum is with small circuits. Done properly, aluminum is perfectly fine for large circuits. There are restrictions in some places (at least Montgomery County, MD) with aluminum for branch circuits, but not for subpanels.

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    IIUC, aluminum for branch circuits is just fine too, if the connections are done properly. Of course, AL branch circuits are outlawed in some jurisdictions, but that's a different story
    – FreeMan
    Jan 21 at 13:09
  • Ahhh, AFCI/GFCI, I can't believe I forgot all about that! Hadn't considered aluminum, will have to check out local restrictions to investigate further. Totally agree with making as much future capacity as possible available for expansion. Was planning to add at least an 8 space panel, even if only using the 4 for now.
    – KM001
    Jan 21 at 16:55
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    I'd say 8 space is the absolute minimum. I'll add more... Jan 21 at 17:09
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Do consider future usage - the car several generations away might have 50A or more of charging capacity.

A future car might be capable of reverse-feeding your home at certain peak times of the day as part of load-shifting.

I would suggest exploring the possibility of a completely separate circuit just for charging cars, AND how much the opportunity cost is to ridiculously oversize that circuit.

None of us know what the next decades will hold in terms of vehicles and energy management in the home. If the incremental cost to go up in capacity is small, it may be worth doing now.

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  • Excellent points, but would probably be better as a comment.
    – FreeMan
    Jan 21 at 13:09
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    Great points to consider. Will need to investigate further. I have a reservation for the new F-150 lightning, which advertises this capability, but I wasn't planning to order that option. Between this and other comments, I think I'm going to go all in on charging capability, which is really the whole point of this exercise anyway. My thought process has been "24A is plenty," mainly b/c I currently have a Model Y, and easily top it off every day with the standard 12A 120V cable that comes with the car. 24A is at least 4 times faster, but I know some newer platforms are already beyond that.
    – KM001
    Jan 21 at 17:06
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    "Reservation for the F-150" + "I currently have a Model Y" which validates my hypothetical "2 chargers" line in my answer. Definitely put in big (e.g., 40A 240V) charger circuits for both. The electricity (OK, there are some exceptions with peak demand pricing, but EV charging is still a lot less load than on-demand water heating...) costs the same whether you load it up at 32 x 240 or 16 x 120 but you'll charge 4x as fast. Makes a big difference if you have decent size trips two days in a row. Jan 21 at 17:27

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