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Nema 6-20

Discussion in 'Model S: Battery & Charging' started by dave, Sep 21, 2012.

  1. dave

    dave Member

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    I'm a rather late reservation holder (9,500) that is counting the costs for the Model S. Maintenance, delivery fees, electrical work, etc are all starting to add up, so I'm trying to cut back where I can. Which brings me to this question:

    My garage has already been wired by the previous owners with a NEMA 6-20 outlet. ( I am not an electrician, I googled the plug to see what kind it was!) My electrical panel has 2 20amp breakers, connected together with a piece of plastic. I'm not sure if that means i have 40 amps on the circuit?

    I'm curious if this plug would be sufficient to charge the Tesla, and I can perhaps get out of re-wiring my garage? Seems like there are a lot of knowledgeable folks here, so I thought I'd ask.

    Thanks!

    Garage Plug.jpg Panel.jpg
     
  2. doug

    doug Administrator / Head Moderator

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    You can charge from that... might be a bit slow, though. The continuous power you can draw from that is 240 V * 16 A = 3.8 kW, which is about 10 miles of range per hour of charge.

    There are two 20 amp breakers because you need one for each hot line (if for example one leg got shorted to ground).
     
  3. strider

    strider Active Member

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    As Lloyd said you'd be able to charge at 240V/16A. They have a 6-20 adapter for the Roadster UMC but the Model S has very adapters available at present. Depending on your length of commute you could be fine. Once some of the hoopla dies down you could ask your Tesla rep if they are planning additional plugs for the Model S UMC. Else there is talk of a Roadster-model S adapter so you could potentially use a Roadster UMC.
     
  4. mknox

    mknox Well-Known Member

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    That is a 20 amp, 240 volt outlet. You have a ganged 20 amp breaker because each "leg" of your outlet has to be fused, and a 240 volt outlet consists of two opposite "legs" from your service panel. A typical 120 volt branch circuit in your house has only one breaker because those outlets are fed from one "leg" and a neutral.

    From this type of outlet, you can charge a Model S, but I'm not sure if they have an adapter available for this socket (I believe they do not). You could, in theory, wire up a cheater cord with a NEMA 6-20 plug and NEMA 14-30 socket, and then plug the Mobile Connector into the socket (they do have a 14-30 adapter) and dial down the charging rate on the Model S's touch screen.
     
  5. dave

    dave Member

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    Thanks for the suggestion! 10 miles per hour sounds awfully slow, but I may be able to make that work. Most nights the car sits in the garage for 10-12 hours at a time...

    So another ignorant question... Would I be able to replace the outlet and breakers to get the NEMA 14-50 receptacle, or would I need a cabling upgrade as well? I'm assuming the cabling is going to be the expensive part, as my house and garage are all completely finished and everything is behind the walls on opposite sides of the house.
     
  6. mknox

    mknox Well-Known Member

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    These are all good questions, and things I've thought through myself!

    Unfortunately, the wire between the service panel and this outlet is the limiting factor. It's very unlikely that the original installation included heavier wiring than would be required for a 20 amp circuit. Further, there may not be a neutral wire as the NEMA 6-20 does not require it, yet the NEMA 14-30 and 14-50 do.
     
  7. dsm363

    dsm363 Roadster + Sig Model S

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    If the breaker box is right there in the garage, upgrading to a NEMA 14-50 shouldn't be ultra-expensive. Might be worth getting an estimate.
     
  8. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    The cheater cord is the way to go, but put a 6-50 on the car side of the cheater cord, and get the 6-50 adapter from Tesla. A 14-30 connector has a neutral pin. A neutral that is not connected can be dangerous if someone assumes that they can get 120V, but the neutral is not there. Connecting the neutral to ground can be a work around, but violates current electrical standards and codes.

    Another choice is to install the 6-50 on the wall in place of the 6-20 with the 20 Amp breaker, and label the wall, 6-50 outlet as "20A breaker, 16A maximum, continuous, current draw." The breakers protect the 20A wire and the 6-50 connector is rated for 50A, much more than the breaker. In fact, see what the acutal wire size/insulation is and you might even be able to go up one current step on the breaker.
     
  9. strider

    strider Active Member

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    While wildly not up to code, if this is your house this is by far the cheapest route. You literally go to Home Depot and buy a 6-50 outlet for like $10 and replace the 6-20 outlet, changing nothing else (I know that's what Cottonwood said but wanted to just spell it out). Now that you mention it, this is what I would do.
     
  10. TEG

    TEG TMC Moderator

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    Note, the specs on that outlet are a perfect match for the charger in a 2011 & 2012 Nissan LEAF.
    (Which charges on the slow side...)
     
  11. GSP

    GSP Member

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    10 mph is slow when you need to add some range after work to your 35-mile or 73-mile EV, but it should be plenty fast enough for overnight charging. Unless you drive over 100 miles/day on a regular basis, which is exceptional.

    With a 265-mile, or even a 120-mile, EV you probably will not need to add miles after work or during the day on weekends. You may want to try using your existing 20 amp circuit, and only upgrade to a 40 or 50 amp circuit if you need it.

    GSP
     
  12. mknox

    mknox Well-Known Member

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    The problem with that is that there may not be a neutral wire there. A NEMA 6-50 has a neutral AND ground ping, and I would not recommend connecting neutral to ground. (Neutral and ground are bonded together at the service entrance, but ground conductors are not always the same gauge and the distance of the wiring run can result in voltage differentials between neutral and ground at the socket).

    I'm not sure how the mobile connector cable would deal with a 6-50 if it sensed no neutral.
     
  13. FlasherZ

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

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    #13 FlasherZ, Sep 22, 2012
    Last edited: Sep 22, 2012
    The NEMA 6-50 does not have a neutral. It's a hot-hot-ground connector. Swapping that 6-20R with a 6-50R will work, just label it so that others aren't confused. As mentioned, if the wiring is 10 AWG, you can swap in a 30A breaker to charge at 24A. If you're lucky enough to have a larger-gauge wire, 8 AWG or 6 AWG, you can put in a 40 or 50A breaker. This is all assuming NM-B type wire and 60degC terminals on junctions and breakers. Electricians can help you if you have something else.

    As there is no neutral to sense, a 6-50 will work just fine as long as the car is dialed down.
     
  14. mknox

    mknox Well-Known Member

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    My mistake. I was thinking of the NEMA 14-50. I didn't think Model S supported 6-50, but checking again, I see that it does.

    That would be the way to go (code issues aside).
     
  15. doug

    doug Administrator / Head Moderator

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    Except that outside of your home, NEMA 14-50 is the most useful, so that's the you want to get with your UMC if you ever plan to take it with you. If you're already putting in your own code violating socket, you might as well go with what allows you to buy the least stuff. Just be sure to label the outlet and make sure you're the only one using it.
     
  16. mknox

    mknox Well-Known Member

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    But that goes back to my earlier thought: The NEMA 14-50 includes a neutral, and there may not be a neutral wire in place. In that case, you would only be wiring 3 of the plugs 4 pins.

    If you put a NEMA 14-50 adapter on a Tesla UMC, will the cable/car electronics be "expecting" to see neutral or does it only care about the two hot legs?
     
  17. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    As far as I've heard it cares about all four wires.
     
  18. mknox

    mknox Well-Known Member

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    That being the case, the original poster would be better advised to go with the NEMA 6-50 socket and adapter which doesn't have a neutral and so the UMC would not be expecting to see it.

    I agree that the NEMA 14-50 is more common in the wild, but the cost of an extra adapter is probably a lot less than the re-wiring that would be required.

    Anyone know what the cost of the plug adapters for the UMC cost?
     
  19. cinergi

    cinergi Active Member

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    also not to code but isn't ground effectively the same as neutral in this case? (e.g. connect the neutral pin to ground to satisfy the detection that might happen with a 14-50)
     
  20. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Because the HPWC does not require the neutral wire, most prewires for it are saving some expensive copper or aluminum and only running 3 wires (two wires for 240V and one ground). Because the HPWC is not shipping yet, Tesla is recommending installing a 6-50 outlet (may need a junction box to step down wire size) and putting in 50A breakers for now.

    The danger in not connecting the neutral is if someone uses both 120V sides and puts unequal loads on each. For example a 200W light on one side and a 40W light on the other side. The 200W light will be dim for a moment until the 40W light burns itself up, then the 200W light will go dark. I don't recommend ever using a 14-50 if you don't have a neutral, but if you insist on using a 14-50 and don't have a neutral wire, then connect the neutral pin to ground. This violates code, but at least is safe.

    I am an early signature customer. I asked for a 6-50 adapter and they gave it to me at no charge. I doubt that will last, but it does not hurt to ask.
     

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