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Wire size for wall charger

jcanoe

Active Member
Oct 2, 2020
4,378
4,563
Maryland
jcanoe provided very helpful answers. To add to that, in case you also needed documented info from Tesla:

https://www.tesla.com/sites/default/files/pdfs/installation-guides/nema-14-50-installation-guide.pdf

Circuit Breaker: 50 amps
 Voltage: Single phase, 208-250 volt AC supply, 60 hertz
 Four Wire Configuration: Line 1 - Line 2 - Ground - Neutral
 Conductors: 6 AWG copper wire for circuits up to 150 feet
 Outlet: Use a high quality, industrial grade outlet
 Ground Pin Orientation: Top position of outlet
 Ventilation: Not required
As has been previously discussed, the NEC does not specify ground pin orientation except for hospital installations. This was confirmed to me by my electrician (Master Electrician) who installed my 50 amp circuit and 14-50 receptacle. Given the short, often very short, power plug cord it makes sense to orient the receptacle in whatever position works best.

Example: The description of the Tesla Cable Organizer sold on the Tesla.com site has two photos that show the Tesla Mobile Connector w/ Chassis Holder mounted in two different orientations. It is not clear from the photo which power plug adapter is used in the photo but it is one of the larger plug adapters so probably NEMA 14-30 or 14-50. The same plug adapter appears in both photos so unless the ground pin orientation was changed to match the orientation of the power plug cord in one of the photos the power plug cord would have to be bent 180 degrees to align with the receptacle.

Cable Organizer

In the first photo the ground pin is in the conventional 12 O'clock position; in the second photo the ground pin is in the 6 O'clock position, else the power plug adapter cord would need to be bent 180 degrees.
 
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roblab

Active Member
Jul 15, 2008
3,907
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Angwin (Napa Valley) CA
If you need to ask you need someone else to do it. Not being insulting but power at this level can kill or burn your house down . Get an expert .. really.

Some of us might not be "experts," but I have been around the block more years than most of you here. If I feel confident to look up proper wire gauge over x number of feet, feel able to string said wire to a 250 volt outlet, and have years of experience in wiring houses, personal businesses, etc, I have found that I have no problem leaving the "experts", some near fifty years younger than myself, out of the equation.

I wired my own new garage, put in a sub panel, and ran the wiring for the outlets that I use to charge my Model S and 3. And I'm not a licensed electrician. I'm quite sure my garage will not burn down due to charging my cars. Research shows that garage fires are mainly caused by stored gasoline and dirty oil rags, both of which are absent in my garage. And research shows that those who express fear are often those who don't understand the subject.

I've been charging now for near twenty years, beginning with my RAV4 EV in 2002. Don't plan to ever go back to the high fire danger of owning a gas powered car.
 

Rocky_H

Well-Known Member
Feb 19, 2015
7,309
9,003
Boise, ID
Some of us might not be "experts," but I have been around the block more years than most of you here. (insert lots of unnecessary bragging)
That wasn't directed at you. From your bragging there, you are basically an expert because of the amount of real experience you already have with it, so you're fine and can safely ignore that comment. Whether someone has expertise is frequently unrelated to whether someone is doing it for income as their career or have an official certification for it.
 
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iluvmacs

Member
Jan 27, 2014
519
899
Madison, WI
That wasn't directed at you. From your bragging there, you are basically an expert because of the amount of real experience you already have with it, so you're fine and can safely ignore that comment. Whether someone has expertise is frequently unrelated to whether someone is doing it for income as their career or have an official certification for it.
+100. Someone coming to an online forum to ask extremely basic questions about electrical work in a clearly uninformed manner indicates they are unqualified. Clearly roblab is qualified.
 
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Some of us might not be "experts," but I have been around the block more years than most of you here. If I feel confident to look up proper wire gauge over x number of feet, feel able to string said wire to a 250 volt outlet, and have years of experience in wiring houses, personal businesses, etc, I have found that I have no problem leaving the "experts", some near fifty years younger than myself, out of the equation.

I wired my own new garage, put in a sub panel, and ran the wiring for the outlets that I use to charge my Model S and 3. And I'm not a licensed electrician. I'm quite sure my garage will not burn down due to charging my cars. Research shows that garage fires are mainly caused by stored gasoline and dirty oil rags, both of which are absent in my garage. And research shows that those who express fear are often those who don't understand the subject.

I've been charging now for near twenty years, beginning with my RAV4 EV in 2002. Don't plan to ever go back to the high fire danger of owning a gas powered car.

Sub panel in the garage, so i have a breaker nearby, is the right play. This stuff isn’t rocket science, it’s narrowly applied physics. With diligence, preparation, and attention to detail and safety I don’t think the answer must be “call an electrician.” But it should be “sanity check my plan” and “help me do the first run”, pragmatically speaking.
 
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DonaldBecker

Member
Aug 24, 2020
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+100. Someone coming to an online forum to ask extremely basic questions about electrical work in a clearly uninformed manner indicates they are unqualified. Clearly roblab is qualified.

I don't fully agree. Sometimes they just want to confirm what a local "expert" is telling them, or want to have some basic knowledge going into a discussion with an electrician.

The bottom line here is that 8 AWG might possibly pass with specific limitations, but 6 AWG should be target unless there are specific constraints. If conduit fill, panel limitations, or minimum bend radius are issues, then you might need a second opinion.

Ampacity of wiring and conduit fill are often simplified into quick look-up tables. If you need to push the edge, you can often get a slightly different answer by doing the full calculations and taking advantage of the installation details. Using 90C rated wire and devices instead of 60C is one place that you can gain a few percent. Doing the explicit conduit fill calculations is another, albeit with significant installation pain.
 

iluvmacs

Member
Jan 27, 2014
519
899
Madison, WI
I don't fully agree. Sometimes they just want to confirm what a local "expert" is telling them, or want to have some basic knowledge going into a discussion with an electrician.
Indeed, and I'm good with that... but the tone of the original question on this particular thread spoke otherwise. I could be wrong, but in general I see a lot of really uninformed electrical questions and advice on Tesla forums, which is troubling.
 

TBrownTX

Member
Dec 25, 2020
968
1,137
Dallas, TX
The Tesla gen 3 wall charger had a max charge rate of 48 amps. That requires a 60 amp circuit as 80 percent of 60 is 48. 6 gauge Romex is only good for 55 amps so you would have to use a 50 amp breaker limiting you to 40 amps. 6 gauge thnn wire in conduit is good for 60 amps. This example shows that Romex and write in conduit can have different capacities even with the same gauge wire. If it were me, I would use the 6 gauge in conduit so I could upgrade later if needed.

I went 60A w/ #4 gauge Romex.

Tim
 

MY-Y

Active Member
Mar 4, 2020
1,241
1,411
MD
6-3 NM on a 60 amp breaker is a code issue. It's also odd that they would use a 3-wire. The neutral is not used on the wall connector.

Is your wire in a black plastic sleeve (i.e. NM)? If so, that's a 60* C wire and not rated for a 60 amp breaker.

Is it in a metal shield (MC spiral) or individual wires in conduit)? If so, it's likely OK.
 

mcorf

Member
Apr 21, 2019
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139
Campbell,Ohio
1B368FCD-8024-4BB6-B3CA-DAA80D3D58CE.jpeg
 

jcanoe

Active Member
Oct 2, 2020
4,378
4,563
Maryland
The electrician responsible should correct the wiring error. The quick fix, unfortunately, is to swap out the 60A breaker for a 50A breaker and change the Wall Connector to charge at a maximum of 40A. Not what you paid for but safer than continuing to use an improperly wired circuit with an oversized breaker. Until you can get this fixed just set the Model Y to charge at 40A; you may need to check, set the maximum charging amperage to 40A each time you charge.
 

iluvmacs

Member
Jan 27, 2014
519
899
Madison, WI
I am getting 48/48A when charging. Should I do anything ?
Yes. It's not up to code. jcanoe has the correct guidance here.

For clarity on why 48A charging is not okay: a circuit must be derated by 20% for continuous draws, including car charging. So that 55A wire is not acceptable because 80% of that is 44A. That's the number you can't exceed, per code. There's no setting in the HPWC for 55A circuit, so 50A is the safe setting, and ideally the breaker should be changed to match this. Otherwise, if you really need a 60A circuit for 48A charging, the wire has to be made 4AWG NM-B or else 6AWG THHN in conduit (or similar).
 
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MY-Y

Active Member
Mar 4, 2020
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IMO, I'd want the electrician to replace the wire with the right one. If that's not an option, 44 amps is 80% of that wires rated capacity, so setting the car to 44 amps seems reasonable to me.

I suspect Rocky_H will weigh in soon. He mentioned some fairly obscure part of the NEC that allowed a 60A breaker when a 55 isn't available. I'm not sure if setting the HPWC to 48 is OK in this situation though.
 
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iluvmacs

Member
Jan 27, 2014
519
899
Madison, WI
IMO, I'd want the electrician to replace the wire with the right one. If that's not an option, 44 amps is 80% of that wires rated capacity, so setting the car to 44 amps seems reasonable to me.

I suspect Rocky_H will weigh in soon. He mentioned some fairly obscure part of the NEC that allowed a 60A breaker when a 55 isn't available. I'm not sure if setting the HPWC to 48 is OK in this situation though.
People often get tripped up on this one. Yes, the NEC says you can "round up" to the next breaker size if unavailable and put a 60A breaker on a 55A circuit, but that doesn't mean you can now draw what a 60A circuit allows. It's still a 55A circuit. If the HPWC had a 55A setting, then putting that on 55A wire with a 60A breaker would be code. But it doesn't, so you are stuck with the 50A circuit / 40A charging setting.

Setting the car to 44A will keep it under the limit... though there are stories of the limit being occasionally "forgotten" by the car, and also it does nothing to prevent someone else's car from charging higher if they don't go out of their way to change the setting. Basically... it could be effective if closely monitored, but it decidedly wouldn't be up to code since the equipment is able to take more than 44A if there is no intervention.
 
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