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Thread: Nema 10-30?

  1. #1
    4GETOIL SS70, XS4, xR913 dadaleus's Avatar
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    Nema 10-30?

    Hi all,

    Question for those more electrically inclined than me... I'm trying to figure out how I'm going to charge when I visit my parents' house. (I'm also looking into having an electrician install a NEMA 14-50 in their carport, but I'm not certain I can get this worked out.)

    They have a NEMA 10-30 outlet for their dryer, but I'll have to use an extension to get to it from the car. I can't find a NEMA 10-30 extension though. Nor a 6-30 or 6-50 which are also 3 prong (I know I'd have to limit the amperage to 30 with the 6-50).

    Wondering if anyone here who knows more thinks I could charge off of a 4 prong connection if the ground wire is not connected, such as by adapting the NEMA 10-30 to a NEMA 14-50 (for which I can get an extension cord)? If I go with the 14-50 I know I will have to keep the amperage down to 30 or below. This would also have the benefit that the extension cord is higher amperage than needed which should help avoid errors I would think.

    This is for a model S, but since I doubt anyone has tried this with the S, I'd be happy with an answer for the Roadster. If it works for the Roadster, I'm willing to take my chances that it would work for the S.

    Thanks all!
    -Jason

  2. #2
    Head Moderator / Administrator doug's Avatar
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    Hmm.. I'd try harder with the electrician putting a 14-50 in the car port. NEMA 10-30 omits ground. Sometimes you can ground through the neutral, but I don't know if the UMC will like that (not considered good practice). The NEMA 14-50 plug on the UMC has a neutral blade, but as far as I know that's left unconnected. For 208-240 V, the UMC requires two hots and a ground.

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    4GETOIL SS70, XS4, xR913 dadaleus's Avatar
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    Quote Originally Posted by doug View Post
    Hmm.. I'd try harder with the electrician putting a 14-50 in the car port. NEMA 10-30 omits ground. Sometimes you can ground through the neutral, but I don't know if the UMC will like that (not considered good practice). The NEMA 14-50 plug on the UMC has a neutral blade, but as far as I know that's left unconnected. For 208-240 V, the UMC requires two hots and a ground.
    I'll try, but not convinced it's going to work out. It's at the opposite end of the house from the breaker box (which is not near anywhere I could get the car into). Could be quite a project to get a 14-50 added.

    I'm nervous about the whole ground vs. neutral bit not being an electrical type myself. Tesla does sell NEMA 10-30 and 6-30 3 prong connector for the UMC. So it seems the UMC should accept this one way or another. I suppose I could adapt the 10-30 to 14-50 for the extension, then adapt it back to 10-30 and get an official Tesla 10-30 connector. But if the 14-50 connector would take the output of the extension missing a prong it would be a whole lot easier.

  4. #4
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    stayonline.com has a bunch of different types of extension cords and can even build custom ones, but there's not a lot you can do when you configure one with a NEMA 6-30 plug.

    Using their custom cord configurator, I was able to configure one with a NEMA 10-30 plug and a NEMA 10-50 connector.

    Not that cheap, though. A 25ft 10awg extension cord will cost $160. Of course, even if you built one yourself, you will spend very close to that amount once you source quality connectors, so it's not that bad.

    Still ideally, I'd see if you can get the dryer plug properly grounded as that gives you a lot more options and also gets you up to code and should be safest.

  5. #5
    Leeroy Jenkins sublimaze1's Avatar
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    I agree with all the above - plus:

    (1) Extension cords are a bad idea when you are running 30+ amps. Not saying they won't work, but sometimes you can keep a ladder attached to your roof rack with twine too ...

    (2) A NEMA 14/50 in your main breaker is the best choice. A Square D 50 amp breaker with 6 ga wire (you don't need much of a run if you install it on that same wall) is the cheapest solution. It is still $180-$300 depending. Maybe more in your area. But you home will be less likely to be visited by the men in a red truck.

    (3) anytime you can get more amps to your car, it will charge faster. I have a 220/16.9 plug for a welder in my garage, but opted for the 14-50 due to reading all the wonderful posts in the forum.


    Now, I am not an electrician, so something I have said above may ring perilously in the ears of one who is an electrician. I would gladly accept any criticism if something is awry above.

    WJ

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    4GETOIL SS70, XS4, xR913 dadaleus's Avatar
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    Drees: Thanks. I'm going to check this out.

    Sublimaze1: The problem is the breaker box is on the far end of the house from the carport and driveway. So they'd have to run something like 150 feet of wire on the outside of the house to get to the carport. And I visit maybe 3 or 4 times a year. I think a kluge solution isn't necessarily such a bad thing under these circumstances.

  7. #7
    mod squad TEG's Avatar
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    I have a personal adapter I made to charge my old RangerEV at a friend's shop.
    It has NEMA10-30 plug, NEMA14-50 socket, and the ground comes out as a long wire with a beefy aligator clip on the end.
    (My old Ranger AVCON EVSE has a NEMA14-50 plug on it to be somewhat portable.)
    I clip the grounding wire to the metal wiring conduit that is coming from the breaker box (which is very close to the 10-30 outlet) before plugging in anything else.
    I verified, using a VOHM, basically no resistance between the grounding pin on the 14-50 and the grounding rod going into the physical ground behind the breaker box.

    It all works, nothing has fried, popped, or had any problems - but with that said, I can't recommend anyone else do this.
    Moderator - Roadster, and Future Cars forums

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    Head Moderator / Administrator doug's Avatar
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    I was going to say maybe you can just wire your own ground, but I didn't realize that Tesla is offering a NEMA 10-30 adapter.
    http://www.teslamotors.com/models/charging#/outlet

    So that might indicate they have the ground-neutral thing worked out.

    I'd just make my own extension and make sure the wires connect straight through.

  9. #9
    Model S P2681 qwk's Avatar
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    Now I dont know about a model S UMC since I havent used one, But a roadster doesnt need the ground to charge. I'm guessing that the Model S should be the same.

  10. #10
    S VIN S1049, X Resv S744
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    You really, really need a safety grounding connector of some kind, and I believe that the Tesla chargers will refuse to charge without a ground of some sort (although I can't confirm, I do recall some posts about Roadsters sensing ground faults). You do not want to simply leave the ground conductor unconnected, you need a path to ground to trip your breaker in case of a short of a hot wire to the chassis. Otherwise a human touching the car could create a path to ground and die.

    As Tesla can charge fine on a NEMA 6 series, it doesn't require a neutral, and only draws on the hot pins. In fact, Adelman said on the NEMA 6-20 thread that the neutral was left unconnected.

    I'd recommend 2 approaches, depending on whether you intend to leave the adapter at your parents' home, or whether you want it to be portable.

    1. Semi-permanent use: Do basically what TEG says above... take a length of 10-3 w/ ground. Attach the 2 hot legs and neutral to the correct pins on a NEMA 10-30P plug and NEMA 14-50R receptacle. Attach the bare ground to the 14-50R's ground pin, and attach it properly to a grounding location (either a properly-connected metal electrical box, a cold copper water pipe, metal electrical conduit, or some other source of equipment safety ground). Test this ground by using an ohmmeter between the ground pin on the 14-50R and a known good ground. I would recommend against what TEG did -- alligator clips, even beefy ones, don't always make or keep the best connections -- you can use them, but test the ground EVERY TIME before you use it, as he did. Label the 14-50R with "FOR TESLA CHARGING USE ONLY -- 30A MAXIMUM". Check that the breaker is 30A maximum.

    2. Portable use: If you want to use the NEMA 10-30 receptacle at your parents', you can wire up a cable that has the NEMA 10-30P on one end and NEMA 14-50R on the other end. Tie the NEMA 14-50R's ground and neutral pins together and feed from the neutral on the 10-30P. Mark the 14-50R with "FOR TESLA CHARGING USE ONLY -- UNGROUNDED RECEPTACLE -- 30A MAXIMUM" or something similar. 2 hot conductors must be minimum #10 AWG, ground can be #12 if you're using separate conductors (otherwise just use 10/2 w/ ground). Confirm your parents have a 30A breaker before using, as I've seen NEMA 10-30's on larger breakers before, and you wouldn't want a fire created by accidentally leaving the Model S at a higher amperage that didn't pop the breaker but burned up the wiring.

    Obviously, the use of any device like this is at your own risk, and the proper way to do this is to have a 14-50R properly installed.

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