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Extension Cord Question

Discussion in 'Roadster' started by Pantera Dude, Jan 25, 2013.

  1. Pantera Dude

    Pantera Dude Member

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    I'm planning to make up a 75-100 foot extension cord for charging my roadster. Will 6-3 work or do I need 6-4?
     
  2. Tesla 940

    Tesla 940 Member

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    What voltage/amp are you planning on running through it?
     
  3. Pantera Dude

    Pantera Dude Member

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    I would like to run up to 40 amps at 240 volts with the UMC. My electrical comes directly off the pole which has a transformer on it so I get almost a full 240 volts to the car.
     
  4. Puyallup Bill

    Puyallup Bill Member

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    6/3, 1/8 is a common 50 Amp extension cord used by RVs - molded NEMA 14-50P and R. I don't know about longer, but 50 footers are available from several sources, Amazon for one.
     
  5. Pantera Dude

    Pantera Dude Member

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    Thank you Bill. I presume 1/8 is the diameter of each wire? The 6/3 you mention has 3 wires correct? Not 3 wires plus a ground wire? What does the R stand for after 14-50P? So I guess I could use both a 50' and 30' to get the 80 that I need, I just thought it would be better if I could use one cord instead of two, in order to prevent voltage drop? I have found some 6/3 SOOW black 90C 55 amp 600V NA heavy duty rubber cable in bulk, will that work for my extension cord? It seems that it would since the Tesla adapters, (which I think are essentially short extension cords), have to be reduced to three prongs from four? I know, I know, I ask a lot of questions. :biggrin:

    - - - Updated - - -

    I assume that voltage drop is the reason Tesla reccommends against using extension cords?
     
  6. pgwoosley

    pgwoosley Member

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    Note that the UMC checks for the ground prong actually being connected to ground.

    I do not know if the UMC tests to see if the neutral prong is connected, but the UMC will operate with neutral and ground connected together so long as they are connected to ground.
     
  7. Pantera Dude

    Pantera Dude Member

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    Thanks PG. I wonder if the UMC charging cable is even using the neutral prong at all? Maybe the neutral wire is not necessary? Maybe they are just using the 14-50 plug to be able to get more than 30 amps, which I think the three prong plugs may be limited to? I read something that made it sound like the reason for the neutral is to provide 120V as well? If the UMC is using 120V what would that be for, to operate the LED on the cable? The price is right on the 6/3 cable that I've found, I just don't want blow a couple hundred bucks on bulk cable that won't work.
     
  8. TonyWilliams

    TonyWilliams Active Member

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    6/3 is fine. You don't need a neutral from a 240 volt UMC. Just two hots and a ground.

    RV's need the neutral because there rarely use 240 volts, and instead use two 120 volt 50 amp services, hence the need for a neutral. When wiring up your NEMA 14-50P, just leave the neutral pin out.
     
  9. mitch672

    mitch672 Active Member

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    Although the UMC probably doesn't use the neutral, building a 14-50 extension cord without a neutral doesn't meet electrical code.
    (Channeling "FlasherZ") "if someone was to get your incomplete 14-50 extension cord, and attempt to us it on an RV setup, you would have a pretty big problem, with no neutral, the 120V return current would be routed through the ground, a clear violation of the N.E.C., the ground is only designed for fault current, not the normal load"

    You should just buy the RV 50' and 30' and be code compliant. BTW, "6/3 + 8/1" refers to the 4 conductors, hot/hot/neutral and the ground being 1 size smaller (the #8)
     
  10. ElSupreme

    ElSupreme Model S 03182

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    I plan on building an extension cord. Probably 50' worth. I am not sure if I want to go 50A or 30A right now. But don't mess with your 14-50 adapter. Just spend the $50 and get a 6-50 adapter for your UMC that way you don't have to worry about a 4th wire. You don't have to worry about someone misusing the cord.

    I Really think I am going to get a 50' 8/3 cord (to minimize voltage drop) and put a 10-30 socket on the end, and buy that adapter for my UMC. I don't think the couple of places where I would like to charge really have 50A and if they do I won't need that much anyway.

    This way your car can't pull too much power. Your cord cost drops in half, not to mention the weight.

    Just go 3 connector wire and buy an adapter from Tesla. Much safer for everyone.
     
  11. GSP

    GSP Member

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    Looks like four good options:

    1) buy the RV 50' and 30' cords from Amazon. This is easiest, but the extra connection between the cords is a drawback.
    2) use the 6/3 SOOW cable with 6-50 connectors, convert the plug to a 6-50, and buy a 6-50 UMC adapter from Tesla.
    3) find a four wire cable and make a code compliant 14-50 extension cord
    4) install a permanent 14-50 plug near the Roadster parking spot.

    I would do #4. If portability is needed, then I like #2, with the lighter 3-wire cable.

    GSP
     
  12. Pantera Dude

    Pantera Dude Member

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    So how about this? I change the outlet on the wall back to 6-50, (it was previously set up for a welder). I buy 80 feet of bulk 6/3 wire and make my extension cord with a male 6-50 and a female 14-50? That should make for the minimum amount of connections and it seems that there would be no way for anyone to screw up and get hurt? What do you guys think?
     
  13. pgwoosley

    pgwoosley Member

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    Someone on this site had for sale a 14-50 UMC dongle for sale which had the neutral prong cut off. Upon inquiry, he explained that at each end of his commute had different sockets and Tesla at one point sold no dongle to match a 14-30. So, he cut off the neutral prong (the only prong different between 14-50 and 14-30). (See, NEMA connector - Wikipedia, the free encyclopedia .) He reported that it worked fine with 14-50 and 14-30 sockets. Of course, he had to be sure to set his Tesla's current draw suitably low when using at the 14-30 socket.
     
  14. GSP

    GSP Member

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    The female 14-50 could be a problem someday if someone plugs in a device that needs the neutral wire. Why not use a female 6-50 and buy a $50 UMC 6-50 adapter from Tesla?

    GSP
     
  15. dhrivnak

    dhrivnak Active Member

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    I believe this can be done and I in-fact made a similar plug to charge at my Son's apartment. It worked fine all night with out any faults or other problems. Maybe you can tape over the neutral to remind you and others it is not active or connect neutral to ground. While not code they are combined in the electrical box so I have a hard time understanding where that is a problem.
     
  16. mitch672

    mitch672 Active Member

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    The "problem" is not the usage with the UMC, but what someone else might try to do with your "Franken cord" extension.
    Imagine a unfamiliar person attempts to use it with an RV/Camper, with no neutral the current will be pulled through the ground, or worse the appliances in the RV will burn out. It's the unintended consequences you can't foresee that are the issue... don't you read any of "FlasherZ"s warnings? It's safer to build a proper 3 wire extension and change the adapter on the UMC. If the cord is used for another purpose, it's built properly for anything it could be used for... None of us are going to live forever, someone is going to inherit your stuff, they might not be as electrically savvy as you.
     
  17. Puyallup Bill

    Puyallup Bill Member

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    That female 14-50 without a neutral connection is a problem, as has been stated a couple of times. You can tag it, tape it, whatever, but people don't read tags. Further, I am quite sure you will not find a nice molded female 14-50, and will have to use a box with a normal wall mount 14-50R.

    I'd go the 50' plus 30' extension cord route. The connection is quite tight when new, and I doubt there is much loss there. Added bonus - might be handy to throw the 30 footer in the trunk for extended cross-country jaunts.
     
  18. Botbldr45

    Botbldr45 Member

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    This is exciting ..... Can't wait to see how your idea works.
    Every time I think of using an extension I get mental images that look like Puyallup Bill's picture...... The Tesla God punishing for doing something not recommended in owners manual.
    A safe and useable extension cord would definitely be an advantage when traveling
     
  19. Pantera Dude

    Pantera Dude Member

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    Thanks to all of you for your help. I decided to keep it simple and went with the 6-3+8-1, (four prong), 14-50 option. I bought a 50 foot and 25 foot cord from Amazon. Now I can charge my car where it is most convenient for me. I've been using the cords for a couple weeks and everything works fine. Now I'll have to figure out something for my welder but I'll cross that bridge when I come to it.
     
  20. pbrulott

    pbrulott Member

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    I need a quick way of building an extension cord to plug into an oven female wall plug and to the male NEMA 14-50 side of the UMC. Around 50 feet to charge my Model S.

    Was thinking of buying a female NEMA 14-50 wall plug and connect a 8-3 cable to it and then create a junction box to plug the male connector (don't seem to find a simple male NEMA 14-50 connector in-store, just a pre-stubbed version).

    This is for very very very rare use. any electricical advice?
     

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