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Nema 10-30?

Discussion in 'North America' started by dadaleus, Oct 7, 2012.

  1. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    #21 FlasherZ, Oct 8, 2012
    Last edited: Oct 8, 2012
    Yes; in many, if not most home installations, a NEMA 10-30R is provided from the "service panel" (the main panel, not a sub-panel) directly where the neutral conductor is bonded to ground anyway. Even if it is provided from a sub-panel, the fact it's a 10-30R means it's likely an older system where subpanels' grounds and neutrals were permitted to be bonded per the older NEC. As a result, there is little harm or foul with connecting neutral to ground at the NEMA 14-50R end.

    Where this matters is if the NEMA 10-30R were served off a subpanel with isolated neutral and ground. For an appliance -- especially one that makes contact with earth ground, like a range sitting on concrete, for example -- this could allow stray currents from the neutral to return to ground through the chassis. It really requires another failure somewhere in the system, but I've seen enough failures to create that condition.

    Just like the NEMA 6-20 thread, do NOT do this in any permanent installation; it's a very bad idea and won't pass code. A "cheater cord" as described will work, but may have some unintended side-effects (like minor shocks in certain cases).

    - - - Updated - - -

    Well, you don't *need* a ground to charge. You WANT one for safety. You don't need a neutral here, because the car does not require 120V.

    We're getting mixed up on terminology. I'm using specific terminology for a reason -- safety... stick with me here as the "neutral" and "ground" are NOT interchangeable, which is why I'm making sure the caveats of this whole exercise are understood.

    The "neutral" conductor is the current return conductor for 120V needs on a center-tapped 120V split-phase system and is referenced to earth ground. The "ground" conductor is the equipment safety grounding conductor and is used to ensure there is a very low-resistance path for equipment chassis to safely return current to ground in case of a system failure.

    The "ground" conductor is for safety only and is only intended to carry current in case of a failure so that 1) humans do not become a return path to earth ground for currents, and 2) overcurrent protection devices can open in case of a short. It is absolutely required in today's world for safety reasons.

    You're correct in stating that the NEMA 14-50R will still work if the neutral pin in the receptacle is unconnected, *for charging the Tesla*. But a 14-50R is not unique to Tesla, and you must not assume others will have the knowledge that you have about that pin being unconnected. And finally, the NEMA 10-30R has no ground pin in it -- only neutral -- so tying the "ground" on one end to the "neutral" on the other is something that has to be labeled. That's why I say if you do it, 1) do it only in a cord; 2) mark that cord from here to heaven and back as I state in the preference order above. It is expected for a NEMA 14-50R to have a ground and a neutral connection. If you sell your home, or are incapacitated or die (perhaps at the hand of your own electrical invention), others must know what is present so it doesn't create a hazard.

    Electricity kills and just because it works, doesn't mean it's safe or won't burn down a building. It may seem like I'm arguing about technical details, but unfortunately I've attended the funerals of people who die from these types of mistakes.
     
  2. dadaleus

    dadaleus 4GETOIL P85#S70,FdrX,S85D

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    Seems like a non-cheater cord then would be to get a custom extension cord made with 10-30's (a P and an R) on each end and get the Tesla official 10-30 end to the charge cable. I'm assuming people wouldn't object then? (Other than objecting to using an extension in general, but I'd have it made with 6 gauge wire to make sure it has way more capacity than needed).

    I was feeling like using an adapter to a 14-50 and using that premade extension would just be nice because the extension cords are readily available and cheaper, because that would be a 6 gauge wire, and because it would be more useful if I ever needed to extend a 14-50 (not sure why I would but I always like options).
     
  3. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Yes, but it obviously requires buying a 10-30P adapter, and reports are they're not ready yet. But when they are available, it is the proper thing to do.

    It's a good point and a reasonable strategy. At 50A, #6 copper will keep voltage drop under 2% over 100 feet and as long as you don't coil the cable, you won't have a heat problem. The reason large extensions like this are frowned upon is that repeated manipulation of the cable can cause stretching or breakage and perhaps a safety hazard. Make sure you get the right cable (e.g., rubber cord cable) for flexible use... and be sure to mark your adapter cable properly if it does something the current code doesn't expect.
     
  4. qwk

    qwk Model S P2681

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    You just explained what I have posted all along, just better. Its all semantics. Aren't both the neutral and ground wires tied to the ground bar in the breaker box?

    And, yes the roadster will not charge without a ground connection, so you NEED a ground.
     
  5. drees

    drees Active Member

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    Yep, that's fine - or your option of a 14-50 extension and a short adapter as you also suggested is a good solution since as you imagine a 14-50 extension cord could be more useful.

    Personally, I'm a fan of running a ground to the dryer and upgrading the receptacle/plug to a 14-30 connection. Swapping out the pigtail on the dryer is a simple thing to do if you can get a ground to your receptacle which may or may not be easy!
     
  6. TEG

    TEG TMC Moderator

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    #26 TEG, Oct 8, 2012
    Last edited: Oct 8, 2012
    There are many other threads on this forum discussing various adapters in this area... Removing the neutral from a NEMA 14-50, etc.

    Here is one that is related:
    http://www.teslamotorsclub.com/showthread.php/5881-Spare-Mobile-Connector-a-waste/
    http://www.teslamotorsclub.com/showthread.php/5881-Spare-Mobile-Connector-a-waste?p=72463&viewfull=1#post72463
    (By the way, the old AVCON EVSE that I am using for my old EV does require both 240V and 120V, so I do need the neutral on the 14-50 for that application.)


    I think having joined neutral + ground was done in WWII and for a while after to save copper. It causes some "funky issues" with some wiring, but it did eliminate a lot of wire in old houses by joining the two functions.
     
  7. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    True if you have only one breaker box, but not always for more complex systems. For anything in the past 20 years or so, the neutral and the ground are tied in one place only - at the service entrance (with notable exceptions like detached garages that didn't become fully isolation-required until NEC 2008). Code requires separation of neutrals and grounds, and then a bonding jumper is used to connect the neutral bar to the ground bar in the service panel. If your branch circuit for that 14-50R is fed from a sub-panel, the neutral and ground should be isolated from each other in that panel all the way back to the service entrance.

    That said, if there's a NEMA 10-30R in the home, it also likely means that the system is older than 20 years and neutral is bonded to ground in every panel, and it doesn't make all that much of a difference. But that also creates more of a chance of shock hazard or strange current return paths for a system failure, which is why it's not done anymore. As of NEC 2008, most exceptions for 3-wire service (hot-hot-neutral) have been removed and every feeder extension must be 4-wire.

    Thanks for confirming that. I had read that it checks for ground reference, likely for safety reasons.
     
  8. strider

    strider Active Member

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    I haven't read all the responses but since Tesla comes w/ a 10-30 adapter, don't you just need a 10-30 extension cord?

    On that stayonline.com site you can get a "custom portable outlet box" that has a male 10-30 on one end and a box on the other end w/ a female 10-30 to which you could plug in the UMC. Don't know what length you need so didn't configure one to get a price.

    That seems a lot easier than messing w/ hots, grounds, running new boxes, etc. or am I missing something?
     
  9. qwk

    qwk Model S P2681

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    I dont think that the 10-30 adapter is available yet.
     
  10. strider

    strider Active Member

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    This is key. The fact that a 10-30 is hot-hot-neutral is important if the device connected is going to only use one leg (120V). Many dryers use 120V to run the control panel, timers, etc. so it should stay hot-hot-neutral. However, if the device connected will only use 240V (like a Tesla UMC) then you can run a 10-30 hot-hot-ground. I am going to do this in my house as I don't have panel capacity to run a 14-50. I will label the outlet "240V EV charging only" or something. It will also help that the outlet will be in the rafters so little chance of someone plugging in a dryer :)
     
  11. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    Right. In the NEMA 6-20 thread, I noted one such case of "funky issues". Where appliances bind the chassis to the neutral (old 10-30 and 10-50 based appliances), you can create a situation where returning current through the neutral is enough to be felt. You learned pretty quickly not to touch my great-grandparents' double oven and the stainless steel sink at the same time, or you'd get a small share of the current returning to ground, but certainly enough you could feel it. It wasn't a hard shock (as in hot shorted to chassis), but it was a tingle. My great-grandfather always said "well, then don't touch both at the same time!" :)

    - - - Updated - - -

    Be very careful here... this is against code. I don't know which SFBA city you're in, but most of them require permits for this type of work (at least when I lived in PA and SJ they did), and adding a NEMA 10-30R as new (instead of replacing an existing receptacle) won't pass inspection. If you sell your home without removing it, the buyer could force a code upgrade on your dime. In some jurisdictions, there are penalties, and/or the buyer can force the entire system to be brought up to current code on the seller's dime. So just... be careful. And if you do it against code, erm, remember to remove the circuit and receptacle before selling. :)

    Why not install a 14-30 instead, and bring a ground with it?
     
  12. TEG

    TEG TMC Moderator

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    #32 TEG, Oct 8, 2012
    Last edited by a moderator: Mar 13, 2016
    Be very careful not to mix up a TT-30 with a 10-30.

    As FlasherZ said, the 240V 10-30 should have an L-shaped Neutral+Ground like this:
    l-shape2.jpg

    The TT-30 ("Travel Trailer") socket found at campsites is 120V and looks like this:
    tt30a.jpg
    Determined individuals have been known to force one type into the other (as they almost fit), usually with bad results such as burning out equipment.



    You find those TT-30 to 14-50 adapters all over the place as many RVs have a NEMA14-50 plug and you can "get by" at a 120V campsite by taking the TT-30 [email protected] and sending it to one hot on the NEMA14-50. (So half of the stuff in your RV powers up...)
    So those TT-30 to NEMA14-50 "dogbone" adapters only provide 120V, and are wired differently to the NEMA14-50 than you would with a 240V 10-30 adapter cable.

    (By the way, way too easy for a big RV to overload one NEMA5-15 or 5-20...
    Those poor sockets and breakers at RV parks get a real workout over time...)

    - - - Updated - - -

    Yes, I have personally experienced minor shocks of that nature before. Also, some sloppy wiring has hot and neutral reversed on the NEMA5-15s, and with chassis grounds you have to be careful if nearby appliances are on seperate legs of the split phase. (Bad idea to plug in a older stove/oven/fridge on a long extension cord from the other side of the house!)

    You have to be careful with this stuff - there are lots of things that can go wrong...
     
  13. strider

    strider Active Member

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    Sorry, re-reading my post my tense grammar is not very clear and there is some background info. I had two 6-30 outlets (hot-hot-ground) installed when we moved in last November. One for the Roadster and one in preparation for the Model S. 30A was chosen because of panel amperage limitations - it would have cost a fortune for a new panel and we don't drive enough to need more than 240/24A charging. 6-30 was chosen because that is what I was using for the Roadster at my last house and I already had the adapter.

    Then I learned that Tesla wasn't going to offer a 6-30 adapter for Model S so now I'm kind of stuck. The wiring and everything is already run w/ just 3 wires for the 6-30 so I'm not sure how hard that would be to retrofit. Plus it seems like a waste of wiring since Tesla doesn't use the neutral anyway. So my plan is to swap the 6-30 outlet for a 10-30 (this is what I meant by "going to" in my post - my Dad is coming out to visit and will offer advice/help as he's done this kind of work before). I can always just swap the 6-30 outlet back into the box when I move out.
     
  14. dadaleus

    dadaleus 4GETOIL P85#S70,FdrX,S85D

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    Update:

    I found out that I couldn't get a 10-30 to 14-50 adapter made given the electrical code issues. And I'm not up for making it myself.

    So based on this and the concerns in this thread I had decided to try and get a 10-30 plug from Tesla, and have a 10-30 6 gauge extension cord made.

    But turns out Tesla isn't making a 10-30 for the S. (Must not have sold many for the Roadster.) They are doing a 6-50 though, which is also three wire, and I can get a 10-30P to 6-50R cord made, so I'm going that way.

    Let me know if anyone thinks this is a bad call.
     
  15. doug

    doug Administrator / Head Moderator

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    Hmmm... well that's exchanging ground for neutral again. Might be ok. Is Tesla offering any guidance?

    My guess is, though, that if there is any problem, the car will simply refuse to charge rather than causing any damage.
     
  16. dadaleus

    dadaleus 4GETOIL P85#S70,FdrX,S85D

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    See, this is the stuff I don't understand... I thought the point was that in a 3 wire the neutral and ground are the same thing. But from your response I guess not. Surprising that I can get a 10-30 to 6-50 adapter then. I hate to spend the money to do this if we think it won't work?

    Would it be better (and within code) to have an electrician wire the back of the 10-30 to a 14-50 and run the 14-50's ground to a ground pole? What I'm trying to avoid is running a 250 foot line across my parents house to the breaker box.
     
  17. JakeP

    JakeP S P4996 / X P6028

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    Where did you all see that Tesla was not going to produce a 10-30 adapter? That is bad news for me also, as 10-30 was my overnight away-from-home charging plan at two separate road trip destinations. And I was following this thread because I was also facing pretty tight distance-to-plug issues.
     
  18. drees

    drees Active Member

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    On a 10-30 the neutral/ground are shared, but they are not the same even though the wire is bonded back at the main service panel. On a dedicated circuit like a dryler outlet, it's not really a big deal in practice, but if it weren't it could definitely pose some safety issues.

    This is no longer up to code, but old buildings are grandfathered in. This is why it's difficult to find a 10-30 adapter or extension cord - you're going to have a hard time finding someone to sell you one and it's certainly won't be UL listed if you do find one. I looked around - can't find any pre-made 10-30 extension cords for the same reason.

    As I said before, technically if you get a ground run to your dryer outlet, you should upgrade it to a standard 14-30 dryer plug and replace the plug on your dryer to match. Whether or not this is technically easy - you'll probably have to get a couple electricians out to check. If the dryer is attached to the same building as the main panel - it probably means running new wire all the way back to the service panel, but I'm not an expert on current codes and they can vary depending on your local jurisdiction.

    The easiest route will be to get a 10-30 -> 14-50 adapter as someone else previously mentioned with the neutral/ground bonded on the 14-50 adapter - then go ahead and buy the suitable length 14-50 extension cord.

    You might inquire with John @ EVSEadapters.com: Electric vehicle adapter cables. I bought a L6-20 bunch of adapters from him for my LEAF - I'm sure he'd be willing to custom build you a 10-30 -> 14-50R adapter.
     
  19. dadaleus

    dadaleus 4GETOIL P85#S70,FdrX,S85D

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    #39 dadaleus, Oct 9, 2012
    Last edited: Oct 9, 2012
    Actually they are the ones that said a 10-30 > 14-50R is problematic. He didn't absolutely say no, but he was going to have to talk to some people and I switched to the strategy of having him make a 10-30 extension which he was happy to do. But then I found that Tesla only does a 6-50 or 14-50, but not a 10-30. He was then willing to make a 10-30 to 6-50 extension for me. So I'm just trying to figure out if that's an issue. If neutral and ground are bonded anyway, I don't see why it would be, other than that the cord should only be used with a Tesla. (Which isn't a problem--heck what else would someone use this bizarre cord for anyway? But I can label it Tesla use only for sure.)

    So I'm trying to determine if this plan is any problem. I'd much rather do that than try and interfere with my parents' house.

    - - - Updated - - -

    Tesla told me when I tried to order one. They are only making 14-50, 6-50, and 5-15 NEMA plugs for the time being.
     
  20. drees

    drees Active Member

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    If he'll do that - go that route and you'll be good to charge!
     

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