Model S

Watch out for this when installing your NEMA 14-50

edited November -1 in Model S
We recently had our NEMA 14-50 outlet installed in our garage in preparation for the MS. We used our regular electrician (who is very good) and sent them to the website to download the installation guide. They came, figured out how to run some of the wire inside the wall/ceiling so we'd have less conduit and did a beautiful job. Then I noticed the breaker they put in was 40A. We called them and said, "isn't that supposed to be 50 amps?"

Even though they saw the installation guide early on, it turns out that when they were making material preparations they saw the icon on the charging page (under calculators) that says NEMA 14-50, 240v | 40A. I know why it says 40A there (because the car draws 40), but that can be very misleading if everything is not double checked.

And it wasn't just the breaker they had to change... they had run 8 AWG wire instead of 6 AWG (since 40A only needs 8). So they had to come back, pull out the wire, run a new one and install bigger conduit.

Don't let this happen to you!


  • edited November -1
    I also had trouble with an electrician who was supposed to be "up" on the HPWC. The first thing he did was tell me to try and return the HPWC. He never opened either of my panels and shot me a bid for running new wire the length of the house and hanging a 14-50 even though I was adamant about using the HPWC due to all of its built-in safety features.

    Had he opened either panel he would have seen 00 gauge wire between the two capable of 145A and a minimal max load at the sub panel. I decided to do the job myself with heavy copper cable from the sub to the HPWC location, add a 90A breaker in two blank positions and set the HPWC for 80A service which it then de-rates to 68A. A perfect, code, safe installation. Total cost for materials was $165 versus $2k to do it all wrong.

    To be fair, the guy was used to the new construction in the north part of town which is all stucco and 14 gauge wire. I have an older home originally built by the developer for himself and back when copper was dirt cheap. He made a bunch of incorrect assumptions rather than looking at what was there and that alone is a bit scary.
  • edited November -1
    Behooves us all to get smart about this. Another thing to watch for is to make sure the electrician installs the receptacle with ground pin up.
  • edited November -1
    @proven : If your electrician installed a NEMA 14-50 outlet on a 40 amps breaker/wire, then he is NOT "very good". It is a major mistake. An outlet have to handle every devices designed for such an outlet. Whether the UMC drives 40, 30 ou 5 amps is pointless. Don't accept any extra fee for HIS mistake.
  • edited November -1
    @stevenmalfert -
    good point. I received my new S85 yesterday, drove it home, went to plug in and ... the ground pin was NOT up as it was supposed to be. Needless to say I was upset- called the electrician who put it in and they are on the way out now to swap out the old one for the correct one.
    I should have examined it at time of installation but they assured me the "knew what hey were doing"
  • edited November -1
    @_thierrY Yes he's not following the code either.
  • edited November -1
    @proven. Leave the 6 AWG wire in. It is a better choice than pulling it to put the 8 AWG wire. Makes no sense. I am assuming the connection can accept the 6. Less voltage drop a d wire runs cooler.
  • edited November -1
    Time for a new electrician. Is your electrician licensed?

    There is nothing special about a "Tesla" NEMA 14-50 install.

    The orientation of the outlet is personal preference - so if you have a preference you can tell your electrician. The ground pin can be oriented up, down, left, right, or even at a 32.7 degree angle if you want.
  • edited November -1
    I installed my own. I'm not an electrician but I did stay at a Holiday Inn last night!
  • edited November -1
    It is not confusing, it says clearly on the installation guide from the webpage:

    Current: 50 amp circuit breaker / 40 amp continuous draw

    There is also a picture with a text saying Ground On Top

    Get en electrician who can read :)
  • edited November -1
    cut directly from the guide:
    To take full advantage of your Tesla Mobile Connector, work with
    an electrician to install a NEMA 14-50 outlet where you plan to park
    your Model S.
    To ensure uninterrupted charging at full power, the circuit breaker
    should be rated for 50 amps.
    You’ll find that charging your car is a lot like plugging in your cell
    phone. For the best experience, we recommend plugging in each
    evening, or when convenient.
    g Voltage: Single phase, 208-250 volt AC supply, 60 hertz
    g Current: 50 amp circuit breaker / 40 amp continuous draw
    g Code: Circuit installation should meet National Electric Code
    (NEC) wire and breaker ratings. In general, this means 6 AWG
    wire for installations under 100 feet
    g Ground Fault Circuit Interrupter (GFCI): Not required
    g Service disconnect: Not required
    g Outlet: Install within 15 feet of driver side taillight (vehicle is
    over 16 feet long) and minimum 18 inches above the ground
  • edited November -1
    @Tes-s : you right, orientation is a personnal preference...

    <a href=;

    <b> NEMA "default" </b> </a> is ground DOWN. However, Tesla decided to put the ground UP. adapters are correctly swaping back the ground in the Tesla orientation.
  • edited November -1
    @Kimscar: I think you mis-read my sentence. They put in 8 AWG first, which is not up to code for 50amps.

    @Olof: Yes the guide is very clear. But if you read my post was that in returning the website to prep materials (one thing I didn't say was that it was a week later) they saw the other page first and thought it meant they should install a 40A circuit.

    They did say afterwards that they thought it was strange that it was asking for 40A, but they saw that on the website and went with it.
  • edited November -1
    Either way you look at this (bad electrician vs stupid mistake), I was just posting it to give warning to new owners to make sure it's done correctly.
  • edited November -1
    I'm not a trained electrician, but even I know that you don't put a 50A receptacle on a 40A breaker. Are you sure this guy's licensed?
  • edited November -1
    I'm just weighing in with tes-s, _thierrY, and carlk that this has nothing to do with what you are going to use the outlet for. NEMA outlet types are a very specific standard that specifies the breaker size that must be used for it. Using a wrong breaker size is a pretty serious fail and against code.
  • edited November -1
    NEMA does not publish a default orientation that I am aware of. I have seen diagrams of NEMA outlets showing the ground both up and down.
  • edited November -1
    The first "electrician" I had out (not licensed but recommended by an electrical contractor that only did commerical work)looked at the HPWC instructions then our electrical panel. He came and talked to me scratching his head and looking bewildered, then quickly scurried away saying he would call me with the bid. Two days later he called and said I definitely didn't have room in my 200A service for the HPWC, and he didn't "think" I could even do the 14-50, but in any case couldn't take the job because he was "too busy".

    That was fine because I had already had another guy out for a bid who had previously one HPWC and one 14-50 install for Teslas. He is licensed, installed the HPWC no problem and had it permitted and inspected as of 2 days ago. So we are good to go for the S85 which we are picking up **tomorrow**.
  • edited November -1
    What would the position of the ground matter?: answer please to someone that has little electrical knowledge: me!
  • edited November -1
    Ground uppers say it is for safety ( in case the plug tilts down - the ground will still be in contact). However, I think the industry addressed this by just making the ground pin longer - then it would be first and last to contact no matter the orientation.

    I am not an electrician, nor do I play one on TV. But I have been zapped with no effect no effect no effect no effect.
  • edited November -1
    It's a matter of gravity. The plug on the UMC is shaped like an L. If the ground is up, then the cord hangs down correctly. If the ground is down, then the cord points up, but gravity is pulling the cord down, which places torque on the plug and causes the cord to hang awkwardly.
  • edited November -1
    #6 aluminum is what I have, 95 foot run, Voltage drop of 9 volts at 40 amps. If I were doing it knowing that now, I would use #4.
    The wire is also warmer than I would like, in hot weather, but still quite safe. Btw, the warmth of wire and v drop are wasting electricity.
  • edited November -1
    Ground up vs ground down depends on where your outlet is located. In my case, I installed it about 18 inches off the floor, and the cord ran UP to a cord caddy just above it at elbow height. If the plug is to the side or above the cord hanger, you might reorient the plug. It's easy enough. Shut off the breaker, and rotate the plug in it's box. The wires are stiff, but it's done in 5 mins.

    The best way to look at it is the ground should be oriented in such a way as to not make the cable make a sharp bend at the NEMA 14-50 adapter end when it's in it's resting position. This provides minimal strain at the cable to adapter interface.
  • edited November -1
    And if you were going to have the UMC cable run at a 45 degree angle, you could simply install the 14-50 on an angle. It would look a little odd, but code and standards do not specify an orientation.
  • edited November -1
    "Licensed" vs "unlicensed" means nothing. There are plenty of good unlicensed electricians and just as many bad licensed ones.
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