Watch out for this when installing your NEMA 14-50

Watch out for this when installing your NEMA 14-50

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!

johncrab | 26 juni 2014

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.

stevenmaifert | 26 juni 2014

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.

_thierrY | 26 juni 2014

@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.

goehring9 | 26 juni 2014

@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"

carlk | 26 juni 2014

@_thierrY Yes he's not following the code either.

Kimscar | 26 juni 2014

@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.

tes-s | 26 juni 2014

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.

Rheumboy | 26 juni 2014

I installed my own. I'm not an electrician but I did stay at a Holiday Inn last night!

Olof | 26 juni 2014

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 :)

Olof | 26 juni 2014

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

_thierrY | 26 juni 2014

@Tes-s : you right, orientation is a personnal preference...


NEMA "default" is ground DOWN. However, Tesla decided to put the ground UP. adapters are correctly swaping back the ground in the Tesla orientation.

proven | 26 juni 2014

@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.

proven | 26 juni 2014

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.

BrassGuy | 26 juni 2014

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?

Rocky_H | 26 juni 2014

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.

tes-s | 26 juni 2014

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.

BiffandSully | 26 juni 2014

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**.

TexasTesla | 26 juni 2014

What would the position of the ground matter?: answer please to someone that has little electrical knowledge: me!

hsadler | 26 juni 2014

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.

triss1 | 26 juni 2014

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.

jamestily | 26 juni 2014

#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.

jbunn | 26 juni 2014

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.

tes-s | 26 juni 2014

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.

mrspaghetti | 26 juni 2014

"Licensed" vs "unlicensed" means nothing. There are plenty of good unlicensed electricians and just as many bad licensed ones.

Bobrrr | 26 juni 2014

Yeah, just like drivers. Lots of really good drivers out on the roads today are unlicensed. And lots of bad drivers are licensed. It means nothing. Right!

mcdonalk | 27 juni 2014

proven & olaf:

To what installation guide are you referring? I can't find any installation information for a NEMA 14-50 connector and circuit on the Tesla web site (which doesn't mean that it is not there).


Theresa | 27 juni 2014

Kimscar; You misread the OP. 8 AWG was installed and needed to be replaced with 6 AWG. I had to re-read it myself because I thought the same thing first time reading it.

gfb107 | 27 juni 2014

Found them under Model S / Charging / Installation

ModelS3P | 27 juni 2014

Doesn't the "50" part of NEMA 14-50 tell you exactly what type of breaker to use?

NEMA nomenclature: the numeral following the hyphen is the rating of the device in amperes.

Rocky_H | 27 juni 2014

@Longhorn92, yes, that's it exactly. For NEMA outlets: 5-15, 10-30, 14-30, 14-50, the second number is always the breaker rating, which is why this is such a facepalm moment that someone who calls himself an electrician would not use the right one.

ir | 27 juni 2014

It also sounds like permits and inspections were not involved. This should have been caught by an inspector and the "electrician" should have had a new exit ripped in their behind.

At best, your new Tesla would trip the breaker on first use. At worst, it would draw 40A overnight and fry the breaker or burn down your home when the wires overheat!

karmamule | 10 juli 2014

I wish I had noticed this thread before having my 14-50 installed today. I had sent my electrician the Tesla guidelines, and at the end of the install he mentioned he'd used 8 gauge instead of 6. I thought to myself "Oh, 8 must be better than 6 (higher number), so he's being extra cautious, great!"

Only after I stumbled across this thread and then read others did I realize he had made a *cheaper* choice. I called him and complained, and he said I'd be fine (50' run through cool basement area), but after a bit more protesting then said he wanted to make sure I'm happy so would replace the 8 with 6 and eat the cost of the 8.

Given the short run in a cool place am I still right to insist on 6?

JimR-RedwoodShores | 10 juli 2014


Get the thicker (lower gauge) wire. Be sure it is copper, 6 awg (not aluminum). Folks can argue about it.... but there is no downside to going with the larger wire. ...and with 50 feet, you'll probably have a smaller voltage drop as well... which will only leave you happier (and charging faster!)... and sleeping sounder at night.

Dan L | 10 juli 2014

@jamestily - a 9V drop at 40 amps means your wire is dissipating 360W.. no wonder it's warm!

To put that into perspective and help justify heavier gauge wire for the forum, if you charge 4 hours per day and your electricity costs 0.15 kWh, that turns into about $80 a year to get electricity from your panel to your car.

tes-s | 11 juli 2014

@karmamule - yes! If they put in a 40a breaker, that is still not good enough. You (or someone else) could put a 40a continuous load on it thinking the 14-50 outlet was wired for 50a.

The 40a continuous load is not code on a 40a circuit. The very smart UMC would be fooled and default to drawing 40a.

People prefer copper (I insisted on it), but there is no problem with aluminum wire. But the gauge is physical size, not current capacity - so the same gauge aluminum wire does not have the same current rating at copper. If you have aluminum installed, just make sure it is the appropriate size.

karmamule | 11 juli 2014

Thanks @tes-s and @JimR, I'm glad you mentioned about aluminum vs copper because I could imagine him using that so I'll make sure he gets copper 6awg. At least he did put in a 50a breaker so that's all set.

tes-s | 11 juli 2014

I do not believe 50a breaker with 8awg copper meets code, though it "may" not be a huge problem depending where/how the cable is run - but that does not make it right, and not a risk worth taking. Should never have put a 50a breaker on an 8awg run.

Interesting on how electricians will sometimes do things like that, but when you want to put a 100amp HPWC car charger on a 200amp panel, they suddenly take a very conservative approach. I don't get it.

karmamule | 11 juli 2014

@tes-s, I wonder if they mistakenly equate the NEMA 14-50 install for a Tesla to things like dryers or stoves, which they have lots of experience with, and relax a bit more than they should; whereas it's much more out of the ordinary to have something as massive as an HPWC in a home environment so they treat it with the respect it deserves.

Kutu | 11 juli 2014

I used #4 wire for a 25" run, for my 14-50, just to be safe. --It was a pain in the &%# to pull thru the conduit and make terminations.

Thom EM | 11 juli 2014

Alas, my electrician is no better. Two dead garage outlets, a dead floodlamp, a dead generator interface, and a dead telephone outlet, and I still hired him to install my NEMA 14-50. And he got that one right! Go figure...

karmamule | 11 juli 2014

@Thom EM, it's amazing how much the lure and convenience of habit can convince us to put up with that sort of thing!

Surf | 1 januari 2015

Going to bump this thread since I had a problem here as well. My electrician installed the NEMA 14-50 exactly like the photo on the Tesla website. This has the "G" at the top. I think the website should adjust this and mention that if the outlet is placed above X height (maybe 18 inches?) the G should be facing down so the heavy cord won't pull awkwardly as it has to curve up toward the sky before it comes to rest on the floor of your garage. I will try and post a photo later of what this looks like. | 1 januari 2015

Attention to detail always a good thing. Use of Aluminum wire not so much. Not recommended. Aluminum oxide forms at connections and is an insulator. Connections can heat up or eventually open up. Not a good thing. Copper is good.

ROCDOC | 1 januari 2015

Sure, copper is better than aluminum but recognize that you probably have aluminum wiring in your house already. The wires that lead to your house are most certainly aluminum. Subpanels in your house are probably wired to the main panel by aluminum conduit. Mine has it. My electrician, who is very seasoned, assured me that it is not only code, but very standard to use the proper gauge aluminum to connect subpanels to the main breaker box. That is what he did for me -- ran very large gauge (not sure what) aluminum from main box about 60 feet to 100 A subpanel (may add HPWC in the future) in the garage, from which he used 6 gauge copper to connect the 50 A circuit to the Nema 14-50. I charge consistently at 238V and 40 amps, 29-30 miles per hour. Maybe I will have problems in the future, with the aluminum connecting subpanels but hopefully not.

Opafiets | 1 januari 2015

I did rock & roll shows for a number of years and got to deal with all manner of temporary connections, plugs, cables, good electricians and awful. A few thoughts.

Get your cable or a loaner from your dealer and give it to your electrician when they do the install. This will help with orientation and placement.

As mentioned NEVER use aluminum. Really surprised when I saw this.

Tight radiuses with larger cables can have an impact on the current capacity and voltage drop. I believe this is due to stresses along the surface of each piece of copper in the cable.

Longer runs can result in significant voltage drop as discussed above. Larger AWG will lessen this considerably. High temps can also increase voltage drop and cause for larger wire gauge.

Consider having them install a secondary panel in your garage while they're at it. Doesn't (or shouldn't) cost a lot more and will give you or future homeowners some options for power for other garagy/shoppy kind of things.

I don't believe it is against code (NEC) to install a smaller breaker. We'd see this quite often in smaller venues and learned to always check the breaker size before hooking up and our tour electricians said that this wasn't against code in most states (1970's/80's though so may have been updated since).

Also, I'd think (big question here) the Tesla onboard charger would likely see enough voltage drop in a heated wire to lower its draw and avoid a tripped breaker (assuming the breaker is sized properly for the wire gauge)?

EnglishGuy | 1 januari 2015

My electrician made the same mistake with a 14-50. In my original text I said I needed 40A for the car (which is true), but I gave home the Tesla instructions for clarity when he came. He didn't read it. I got 40A breaker and #8. I called him back and he upgraded for 50A and #6. He told me he had done an install the week before with 40A/#8 and that customer must not have noticed. I was not willing to limit the current to 32A. It seems to be a common mistake so I would urge owners to be explicit - I didn't want to question his know-how by pointing out something so obvious...I wish I had now. It cost me an extra $125 for the thicker wire (60ft run).

FelixMendeldog | 1 januari 2015

I do everything I possibly can myself because many, many times I haven’t, someone who assured me, ‘We know exactly what we’re doing, we’re experts!’ has screwed something up—really badly—in cases which are unrelated to Tesla, but I’ve learned my lessons. Like the shop that ‘repaired’ my boat, launched it, and let it sink because they never replaced the leaking outdrive bellows they for which they charged me.

I agree with others: your electricians skimmed the paper, ran the wrong wire and installed the wrong breaker for 40 amp continuous load—I don’t think they’re very good.

milesbb | 1 januari 2015

(Doesn't the "50" part of NEMA 14-50 tell you exactly what type of breaker to use?)

No actually it does not. Ref NEC 210.21(B)(1). The National Electric Code only requires that the breaker not be sized larger then the 50 amp receptacle rating, smaller breaker sizes are ok. I believe "proven" got a code legal installation, just not one that was fully suitable for his needs. Good communication with your installer is the key. I believe that is the point being made by "proven".