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Tesla wall charger wiring question.

Discussion in 'Model 3' started by Sparky 747, Aug 1, 2018.

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  1. Sparky 747

    Sparky 747 Member

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    An electrician ran cables to a new 240V/40A outlet box ready for hookup to a Tesla wall charger. Rather than call him out again, I'm thinking of doing it myself as it appears quite straightforward. Question. I have one red, one black and one green cable. The white neutral is tucked out of there way. The green is connected to the smaller earthing terminal which leaves the live red and live black. Does it matter which way round I connect them? Looking at youtube videos it look like the red goes to the right terminal (as I look at it) and the black the left.
    p.s I've tested red to black at 240V, red to green 110v and black to green 110V.
     
  2. brkaus

    brkaus Active Member

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    Should not matter. The white can be ignored for this installation and should be capped.

    What gauge wire did they use? What circuit breaker? You mentioned 40a...
     
  3. Sparky 747

    Sparky 747 Member

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    Not sure of the gauge but he's a qualified electrician and he knew what the wiring was for (the gauge is pretty substantial). It's connected to a 40A breaker.
     
  4. AWDtsla

    AWDtsla Active Member

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    Red and black are interchangeable. You should hook up the white, in case someone plugs in something other than a Tesla someday.
     
    • Disagree x 1
  5. Darscot

    Darscot Member

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    Does it make sense to install a wall charger with a 40 amp breaker? Can't you pull that with the portable charger and and a dryer plug?
     
  6. scottm

    scottm Active Member

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    If you're doing DIY on wall charger... going from what I know about my wall charger, the first gen 80A beast... you want to be sure of using anti-oxidant electrical connection lube / coating smeared on the stripped wire ends, and torquing down the wiring lugs to a specified setting. Not doing either of these things correctly can create too much heat at these connections over time.
     
  7. boaterva

    boaterva Supporting Member

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    If this is for the HPWC, there is no place for the neutral. If it’s a 14-50 socket then there is. See my sig for Flasher’s excellent FAQ on all of this and more.
     
  8. JPP

    JPP Active Member

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    He is not installing a NEMA 14-50R. He has the j-box and the electrician smartly pulled the neutral. So the neutral can stay capped off in the j-box.
     
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  9. Runt8

    Runt8 Active Member

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    I was assuming he meant it should be hooked up in the circuit panel so that in the future the wall connector could be replaced with a NEMA outlet.
     
  10. TexasEV

    TexasEV Well-Known Member

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    No. A “dryer plug” uses a 30A circuit and the car will draw 24A. With a 40 or 50A circuit and a NEMA 14-50 outlet, a Gen 2 UMC will draw 32A. But a 14-50 is really meant for a 50A circuit unless it’s in an enclosed space like an oven. You wouldn’t want someone plugging their RV into one that’s only in a 40A circuit, or a Gen 1 UMC for that matter.

    The bigger question is if you’re going to the expense of installing a Wall Connector (not charger), why did you have only a 40A circuit installed?
     
  11. Sparky 747

    Sparky 747 Member

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    I have limited available amperage in the barn. 40 Amps is all he could give me without pulling through new cable. 32A charging rate should be fine for me.
     
  12. SSedan

    SSedan Member

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    Redundant charging options is good planning.
     
  13. voip-ninja

    voip-ninja Give me some sugar baby

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    It really doesn’t matter which hot lead goes where since the charger is single phase and uses the non active hot as the return path in the charge phase.

    Neutral should be capped with a proper wire nut in the junction box or pull it through the conduit entry in the wall connector and cap it there.

    Improper termination of the unused neutral or under torquing the lugs would be my primary concerns.

    I just completed a similar installation so let me know if you have any other questions.

    The wire terminals on the connector are very very hard to get larger gauge wire into so I would recommend that you pre-bend the wires, loosen up the terminals as far as they will go without forcing them, then feed the wire in as far as possible.

    When you start tightening the terminal screw if it doesn’t start to bite the wire pretty soon you will want to pull the wire out and try again.
     
  14. Darscot

    Darscot Member

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    This is what I was getting at, pulling 32A in a wall connector is pretty crap ROI.
     
  15. insaneoctane

    insaneoctane Active Member

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    Torque the wires down real good. Poor connection and, thus, heat are the enemy of this install.
     
  16. ℬête Noire

    ℬête Noire Active Member

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    I played around with the plug-in versions. The handiness of a station, not having to work about the plug side of the matter and a lump on the cord, is a non-zero thing.

    That's why I went with a station for the J1772 connector in my garage, although in that case it was an easier call because I would have had to purchase the UMC equivalent anyway. The price difference was relatively minimal by the time I added in the cost of the box and the plug itself (because do NOT get the cheap one that is meant to hold the same dryer cord for years at a time, usually unseen much less touched, get the $30-ish that'll hold up to repeated plugging and unplugging).
     
  17. gregd

    gregd Active Member

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    As noted, the red / black wiring doesn't matter, and I understand the limitations (amperage) that you're dealing with. 32 amps charging is honestly just fine for most situations. I have a 50 amp circuit (40 net charging) to a 14-50 outlet, but have the car turned down to 24 just to be nice (everything runs cooler), and it's quite sufficient.

    If you intend to finish the job yourself, don't forget to program the wall unit for the right current (so it doesn't let the car think you have more than you do), and also be sure to have the city/county do the final inspection and sign off on the permit. Otherwise, there could be implications for future insurance claims, or disclosure problems when it comes time to sell the property.

    My recommendation would be to just let the electrician finish the job, but watch what he does so you can learn. I'm a little concerned that you were measuring the voltage on the un-terminated live wires...
     
  18. eprosenx

    eprosenx Member

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    As noted by others, a dryer plug is a 30a plug so this would be a code violation to put on a 40a circuit. You could downgrade the breaker to 30a, but naturally my preference is for as much capacity as possible. You can always charge slower in software from the car if you feel the need, but it is good to have max charge speed available for the unforeseen situations.

    I don't see any reasons to use an anti-oxidant on the connections. This generally applies (and is good advice) on aluminum wire, but the Wall Connector IS NOT RATED for aluminum wire - using it would be dangerous! Copper wire does not need anti-oxidant. The correct torque is good advice though.

    The 40a vs 50a thing on a 14-50 gets thrown around a lot, but I want to be very clear: It is fully NEC code compliant (2017 code) to put a 14-50 receptacle on a 40a circuit as long as that is the only receptacle on the circuit (which is a requirement for EV use anyway), and the intended load (the UMC Gen 2 in this case) is not going to draw more than 32a continuous (which is the case with a UMC Gen 2).

    Now, generally, I would always wire up a 14-50 with sufficient ampacity wire (generally 6 AWG) to support 50a just for future proofing (and I probably would also put it on a 50a breaker), but there are cases where putting it on say 8 AWG NM cable (romex) on a 40a breaker would be completely fine.

    Others have sometimes recommended (and I agree with them) that labeling the receptacle that it is only on a 40a circuit (good for 32a continuous) would be a good idea, but it is NOT a code requirement. The UMC gen 2 will draw a max of 32a and be totally happy on a 40a circuit. The issue comes in if someone later plugs in a different EVSE that draws 40a continuously.

    In this case if his electrician wired him on a 40a breaker, there is a good chance they only wired it with 8 AWG NM (Romex) cable. Or maybe at best 6 AWG. So I don't think landing the wires will be too difficult under the Wall Connector.

    I think the original poster can probably successfully do this themselves. It really is not rocket science if you are somewhat handy. I would just throw in that you need to make sure that the wall connector is firmly mechanically connected to the wall so it wont rip off the wall or anything. i.e. It needs to be screwed into wood.

    If the circuit that was added was inspected already, I am not even sure this installation would require a permit (check with your local authority having jurisdiction). It may be classed similarly to installing new wall outlets or light fixtures.

    Do be absolutely sure to set the max power draw via the rotary dial correctly per the install instructions table. Note that on a 40a circuit you can only draw 32 amps from the Wall Connector due to the 125% oversizing rule.
     
    • Informative x 1

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