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NEMA 14-50 to extension cord to NEMA 10-30 charging?

Discussion in 'Model 3: Battery & Charging' started by dc121gw, Dec 15, 2019.

  1. dc121gw

    dc121gw Member

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    I am taking a road trip over the holidays and my host has a standard 5-15 120V outlet and a 3-prong 10-30 dryer outlet.

    I have the 14-50 Tesla charging adapter. Rather than buy the 10-30 charging adapter from Tesla, I got a 14-50 to 10-30 adapter. So I would use the 14-50 on the Telsa mobile charging, and then use the 10-30 adapter on the 14-50 plug. The adapter I bought is listed as being compatible with EV charging, but who knows if these Amazon sellers are accurate.

    My first question is, would cause any problems? The 10-30 is 3 prong. I'm not an electrician, but I believe that 4 prongs are better, being wired to both neutral and earth ground. I plan to alter the car charging settings to lower the current draw to 20 amps, in order to avoid tripping my host's circuit breaker.

    My second question is, if I used a 14-50 30' extension cord, would this cause problems? The extension cord is sold for RVs and is absurdly thick. I don't expect this cord to cause any electrical problems, but you never know.
     
  2. neurocutie

    neurocutie Member

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    sounds fine as a temp solution. the chargers don't use the neutral connection.
     
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  3. ambudriver03

    ambudriver03 Member

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    You could technically charge at upto 24a on the nema 10-30 (80% of 30a).

    Unless there are other appliance on the circuit it should not trip at 24 or less.

    Obviously you can set it down to whatever you feel comfortable.

    And like the previous comment said. Tesla doesn't care about the neutral line. Since the charger runs hot to hot in a 240v connection.

    I bought the tesla bag of adapters for specifically this use case.

    The complication arises if your host outlet is something other than a 14-50 and your extension cord is 14-50... Then you'd need two adapters and to remember to manually turn down the charge rate.
     
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  4. eprosenx

    eprosenx Active Member

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    Yup, sounds like you are all good to go. The RV extension cord is fine. The adapter you describe should be fine.

    The critical piece you have identified is to set the charge rate down to 24 amps or lower. The 30a dryer plug and circuit should not be driven at over 24 amps. This is the downside to third party adapters. But since you need to use an extension cord, this is really the only practical way to do it (who wants to otherwise own different extension cords for every possible receptacle type?).

    You are right that a 10-30 does not have a ground, but since the Tesla does not use the neutral at all, it just uses the neutral wire as a ground instead. They are connected back to the same place anyway... This is even officially sanctioned by Tesla with their factory adapters.

    Have a great trip and do report back on how it goes for people who find this thread years down the road in the Google index!

    P.S. EVSE Adapters sells extension cords specifically for EV’s which omit the neutral altogether. Kind of interesting as it lets you plug into 14-30 and 14-50 receptacles “out of the box”. Cutting one conductor out of the cord sounds nice, but they sell a really thick cord that is probably way overkill still if you just have a 32a UMC Gen 2.
     
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  5. srs5694

    srs5694 Active Member

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    I mainly want to hammer home the advice to turn the charge rate down to 24A on the Tesla. With the NEMA 14-50 plug in place, the Mobile Connector will try to charge at 32A, which will exceed what the house's NEMA 10-30 plug can provide (assuming the wiring and circuit breaker match the NEMA 10-30 socket). At best, this will result in the circuit breaker tripping. At worst, if something goes wrong, it could overheat and cause a fire. Turning it down to 24A in the Tesla should make it safe. This isn't something I'd want to rely on long-term, since the Tesla's settings sometimes reset themselves (mostly after firmware updates), but for a holiday road trip, it should be OK.

    A better solution would be to buy the NEMA 10-30 adapter/plug from Tesla, and if necessary, a NEMA 10-30 extension cord. This will set the amperage correctly in the Tesla without any manual override. Since you've already got an adapter that should work, though, it's probably not worth replicating it for this one trip. If you expect to be plugging into a NEMA 10-30 outlet on a regular basis, though, it's worth getting Tesla's NEMA 10-30 plug/adapter to do it right in the future.
     
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  6. dc121gw

    dc121gw Member

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    Thanks for the feedback. I was going to just buy the bag of adapters from Tesla and not have any worries, but it didn't seem practical to also buy and store extension cords specific to each plug type. The logic was that, when charging away from home, I would just get the chunky 14-50 EV extension cord, which I would use when 14-50 charging was available. If 14-50 was not available, I would terminate the extension cord with the appropriate adapter. In this case, the 10-30 adapter.

    I was going to lower the current draw on the car just to avoid having to troubleshoot a tripped breaker at my in-laws. I didn't know there was a (small) fire risk. That's concerning.

    Now that I've typed this out, I wonder why Tesla doesn't sell an extension cable for the mobile connector itself. Then you could use the real Tesla adapter(s) on the supply side, while also increasing your charge distance with an extension on the car side. Maybe they can't guarantee the safety of such an extension cable?
     
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  7. davewill

    davewill Active Member

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    #7 davewill, Dec 16, 2019
    Last edited: Dec 16, 2019
    There are a couple of J1772 extension cords out there, so a Tesla one could be built. There are a few reasons why I don't expect to see one from Tesla, though.

    1. The connector are expensive, so the product would be, too.
    2. There's no simple way to limit the current from that end, so you either have to trust the end user not to use the cable in a situation where it would be overloaded, or you'd have to only sell an 80a version. You'd also want to be fairly sure it could not be used with or cause a problem at a Supercharger.

    I know that https://QuickChargePower.com sells their J1772 extension in 40a and 80a varieties. They could probably build Tesla ones since, they sell all the parts. However I'd guess at a price tag near $400 (apparently $300 see next post). At a more reasonable price, they will take your mobile or wall connector and extend the cable length, which avoids the expensive parts and the worries about overloading.
     
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  8. ambudriver03

    ambudriver03 Member

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    My garage is 75' away from where I park and charge. I'm running a RV type 14-50extension cord with 6/3 and the Corded Mobile connector. At 40a maximum draw the voltage sags to around 233. (total run from the box is around 150')

    Tesla ELONG™ Tesla Extension Cable

    The 6/3 RV cord is about an inch in diameter and the cabling on the Corded Mobile connector (40a) looks to be about 50% beefier than that of the regular mobile connector.

    PhotoGrid_1576517869062.jpg
     
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  9. srs5694

    srs5694 Active Member

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    Such events are rare, and they should not happen if the breaker does its job. If the breaker is defective or damaged, though, it might fail to trip when it should, which would likely cause wiring to overheat. I seem to recall that there was a particular brand of circuit breaker that was prone to such failures. It's no longer on the market, IIRC, and I don't recall what the brand was, but there's no telling what might be installed in a given house.

    In sum, you'd need a cascading set of failures to trigger such a problem -- plugging a NEMA 14-50 into a NEMA 10-30 (or other higher-to-lower amperage combinations), failing to set the charge rate down, and having a defective circuit breaker. Since you're planning to do the first of those, you should be extra careful about the second. I don't know much about testing circuit breakers, but you could look into doing so if you want to be more confident in that final line of automatic defense.
     
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  10. doghousePVD

    doghousePVD My grandfather’s car

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    A 10-30 plug does not have a ground. The third prong is the neutral, not a ground. Depending on the wiring and loads in the house, the Tesla mobile charger might detect a lack of ground and trip. I have never had that to me while using my 10-50 plug, but just letting you know.

    It is possible your connector is wired from the 14-50 neutral to the 10-30 neutral, leaving the 14-50 ground disconnected. This most likely won't work, as if there is no ground the EVSE will trip. If the vendor asserts it is good for charging EVs, it should work. If it does not work simply connect the neutral line (the "nose" prong of the 10-30) to both the neutral and ground in the 14-50 outlet, or connect it only to the ground. The ground in the 14-50 is the semi-round blade.

    There is no real safety issue, the EVSE trips for safety whether there is a ground or a neutral. The ground and neutral are bonded together at the panel.
     
  11. Rocky_H

    Rocky_H Active Member

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    This could use a little better explaining. You are right that the 10-XX series of outlets don't have an actual ground. It is a neutral, but that was kind of a cheap/lazy way to save wire cost in these outlets and effectively "share" the purposes of a ground and a neutral.

    The Tesla charging system, though, doesn't even have a neutral connection at all. It just has the two pins for some kind of voltage and then a ground that it requires. So for these kinds of 10-XX outlets, it just remaps the required ground that it wants onto that neutral pin for the 10-30 or 10-50 plug and pretends as if it is a ground. Since there is nothing else on that circuit, and the neutral line does go back to the common bus bar in the panel where all of the neutrals and grounds are tied together, the car sees it as the same thing at 0V and doesn't have any problem with it.
     
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  12. doghousePVD

    doghousePVD My grandfather’s car

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    I know we are basically saying the same thing, but theoretically with a 10-30 one was supposed to ground the dryer or whatever separately from the neutral, typically a metal water pipe. Usually that meant the device was grounded without a wire, although I remember back in the day green wires snaked to a copper pipe.

    With the rise of PVC and Pex that stopped working.
     
  13. Rocky_H

    Rocky_H Active Member

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    Huh. I have heard about in wall wiring, it's still common and acceptable to ground things to metal piping. I hadn't heard this about old practice to ground appliances separately. That does make sense what you are saying about the move to most plumbing pipes going to plastic that there isn't an easy ground source in laundry rooms anymore.
     
  14. brkaus

    brkaus Well-Known Member

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    Coming soon extension cord that works on the other side of the EVSE.

    Tesla ELONG™ Tesla Extension Cable

    It has a fuse, so NOT TO BE USED WITH SUPERCHARGING! I doh't recall if this is rated at 40a, 60a, or 80a.

    And to repeat - DO NOT EXCEED 24A on your dryer plug :)

    edit: Oops. Someone linked above already.
     
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  15. ambudriver03

    ambudriver03 Member

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    Zinsco and Federal Pacific Electric Company come to mind.

    Both companies eventually went out of business and there are tens of thousands of these panels on houses throughout the US, especially ones built in the 50s through the 80s.

    My house was built in 1957 and has a Zinsco subpanel on the house (which does not support any 240v loads), luckily the main panel where my power comes in from the utility pole is a SquareD QO panel and had sufficient capacity to host a high amperage 240v circuit (14-50 with gfci) . (hence why I am using a ridiculously long extension cord attached to the 14-50 on the garage)
     
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  16. Runt8

    Runt8 Active Member

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    This thread got me thinking - are there any technical problems with a universal extension coord with various adapters for both ends? The cord could be made of thick gauge wire that supports up to 50 amps (for example), but with appropriate adaptors for both ends it could be used for pretty much any receptacle and with the correct pigtail on the mobile connector, so the appropriate amperage is automatically used without having to set it from the car.
     
  17. ambudriver03

    ambudriver03 Member

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    Basically adapters exist for any situation. The most important would be the ones you'd use commonly at the voltage and amperage you expect.

    A 50a 6/3 RV cord with a 14-50 plug is the most versatile as it can run full hog with the Corded Mobile adapter. But you'd still have to convert and both ends if you wanted to use the tesla mobile connector adapter to automatically reduce current.

    For your example if you had a 14-30 outlet you could use a 14-30 to 14-50 adapter/pigtail
    Then carry the power on the 14-50 extension cord (should be 6 gauge wire) at the terminus you could do one of two things.
    1. Connect the mobile connector with the 14-50 and manually de rate the current (on the charging screen
    2. Connect another reverse adapter going from 14-50 to 14-30 and using the tesla 14-30 plug
     
  18. davewill

    davewill Active Member

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    There's nothing technically wrong with the idea, and many people have done variations of it. It gets expensive and bulky if you buy or make a lot of different adapters as it would typically take three adapters (one for the UMC, one from there to the receptacle of the extension cord, and one more from the plug end of the extension cord to the outlet.

    If I were to do it for the mobile connector, I'd get a 6-50 extension cord, and make my adapter from a 6-50 plug to the other plugs rather than do adapters for both ends. This requires manually dialing down the charge rate in the car, which I would veto it as a daily solution, but for "emergencies" it would be adequate. It works better with something like the OpenEVSE which allows you to configure the EVSE for different amperages. Conveniently, the adapters work whether you need the extension cord or not. To cut down on the number of adapters, you could buy a few plugs like these that can be installed with a screwdriver on the plug end of an adapter:

    https://www.amazon.com/Legrand3867CC5-30-Amp-125-volt-250-volt-Plastic/dp/B000BQW4OS
    https://www.amazon.com/AIDA-Grounding-Interchangeable-Straight-Replacement/dp/B07X9Z5CX5
    https://www.amazon.com/Leviton-5266-C-Industrial-Grounding-Black-White/dp/B001VXU4TC


    The nice thing about having an extension for the Tesla connector (or J1772), is that you avoid all that and it works with public charging as well. If you get ICEd, you can just park in an adjacent space and extend the cord to your car.
     
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  19. dhrivnak

    dhrivnak Active Member

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    I built my own due to this happening and in the 6 years hence I have yet to have needed it.
     
  20. ambudriver03

    ambudriver03 Member

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    I guess in an emergency you could wire up a set of low amperage connectors if you had a bundle of romex (or 10/3 SOOW) and some 6-20 connectors. Being able to switch from 5/6-20 being only a pair of plugs
     

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