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FAQ: Home Tesla charging infrastructure Q&A
- Thread starter FlasherZ
- Start date
Are there any rumors of new wall chargers coming out? We're selling our house and the new owners want my chargers. I've got to pick up two for the new house. There's a 20A dryer plug in there so I could get by if there's any rumors of something coming in the next couple of months.
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israndy
Supercharger Hunter
Just installed one of those v3 Wall Connectors like you can get for $425 on Tesla.com, and it was so easy, 4 feet of 6/2 Romex and a $17 60 amp breaker from Home Depot, took about an hour to mount it on the inside of the wall that has the breaker panel on the outside, could have been faster if I wasn't concerned with the look of the job. Charging at 12kW or 45MPH.
This has been discussed so much. You know that's not code compliant, right? That is only up to a rating of 55A. You can't use that cable for a full 60A rated circuit.
israndy
Supercharger Hunter
I think there is a thing called voltage drop that comes into play, so the shorter a cable you use the less diameter you need. It's the total resistance you are worried about. And if it's good enough for 55A and I never pull more than 48A I'm golden.
No, following National Electric Code is what this is--not voltage drop calculations.
No, that's not how that is done. The requirement from electric code says this. There are continuous loads and non continuous loads.
But for continuous loads, you take the load amps and multiply it by 125% to make the circuit rating you need. EV charging is always defined as continuous load now, so that's what this is. So for 48A, you multiply it by 125%, and you must have a full 60A rated circuit. Your 55A rating doesn't meet that, so it is not sufficient and doesn't meet code.
For non continuous loads, sure, the circuit rating just needs to be at least as high as the load. That's what you were trying to apply, but it's not applicable.
rhumbliner
Member
+1
I’m right there with you. Not only on this forum but all the other EV forums as well. Drives me crazy.
israndy
Supercharger Hunter
davewill
Active Member
It's not very hard to see why this mistake gets made. Most electricians (and inspectors) don't study and memorize the code, they just apply a bunch of rules they've learned over the years. One of those things they "know" is that 60a circuits need 6AWG, which for most applications is true. So they apply that to an EVSE where it's not true. Worse, their installs get approved by inspectors, or they hear of installs that are approved, and it reinforces their "knowledge".
You would probably have a hard time convincing them, since from their POV, if the inspector approves, that's what matters.
I know some of them have picked up bad habits or wrong ideas, but that should be very few. And complying with the rated ampacities should be really straightforward.
...except it's not. It simply IS NOT. This is not true. 6 gauge NM-B simply does not meet a rating of a 60A circuit, ever.
But that's not true. This is what is making me crazy. It isn't anything specific to an EVSE. It has nothing to do with that. If someone had some other big piece of equipment, like a kiln or cement mixer or a giant clothes dryer or welder or whatever, and it required a 60A circuit, you STILL could not use 6 gauge NM-B. It's still wrong and has nothing to do with EVSEs.
It should be so straightforward to get this right when you know the amp rating you need to meet, and you can look up what type and gauge thickness meets it, and just select something that meets the rating.
Yeah. This is frustrating. This mistake is so unfortunately pervasive that it has gotten into a lot of inspectors' heads too.
Sigh. Yes, this is true. But I would hate for people to unfortunately get caught in a situation where an electricity and that inspector incorrectly approves this, but then several years later things need to get inspected for some other reason, and a different inspector gets it correct and fails it.
Total resistance matters in terms of overall efficiency, like how much energy is lost to Joule heating (corresponding to the voltage drop). In this case we're more concerned about preventing electrical fires or failure, so what actually matters is the resistance per unit length. You wouldn't want an undersized wire in your system even though it was only an inch long. That's the inch that's more likely to melt or cause a fire.
Anyhow, 6 gauge should be good for 44A continuous. I'd limit your charging current to that to be safer. You might also change that 60A breaker to 55A for proper protection.
davewill
Active Member
55a breakers don't exist, but that doesn't really matter because the breaker is technically allowed to be 60a. The problem is that the wall connector can't be configured for 44a charging. The best you can do is use a 50a breaker and configure for 40a charging. If you're suggesting changing the car to charge at 44a, that doesn't satisfy code, and given that the car is prone to forget that setting when you least expect it, and it wouldn't stop some other car from plugging in and charging at 48a, isn't a good way to go anyway.Total resistance matters in terms of overall efficiency, like how much energy is lost to Joule heating (corresponding to the voltage drop). In this case we're more concerned about preventing electrical fires or failure, so what actually matters is the resistance per unit length. You wouldn't want an undersized wire in your system even though it was only an inch long. That's the inch that's more likely to melt or cause a fire.
Anyhow, 6 gauge should be good for 44A continuous. I'd limit your charging current to that to be safer. You might also change that 60A breaker to 55A for proper protection.
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I found 55A breakers with a search, but perhaps they're less common. My (non Tesla) EVSE lets me set the the available current by the Amp. Anyhow, I'll take your word for it.
rhumbliner
Member
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rhumbliner
Member
I believe you’re referring to the “upsizing rule” which comes with a lot of caveats. You’ll find that reading the appropriate NEC section or following discussions on sources like Mike Holt’s Forum can be very enlightening.
He did immediately explain those details after that first sentence.
Yes, pretty uncommon. I have seen one kind of EVSE that gives very fine granularity like that of setting the amp level it runs at very specifically, and I guess there may be others, but it's really rare. So that is what we are talking about--if you can actually use a real setting in the device to run at a 44A maximum output, then it will only need a 55A rated circuit, and that is the only way this works. But that is really obscure for people to find EVSEs that can do that.
So apologies if you do have one of those rare devices that can be set for 44A. We just hardly ever see that, and it's almost always people trying to run 48A, which just doesn't work on 6 gauge Romex.
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I assume OP used this 6/2 NM-B (or similar) which is not recommended with a wall connector and 60 amp breaker it looks like? Any recommendation on what should be used instead? Should it be a 4/2 or a 4/3 type wire? Something like this or may be this (cheaper but OOS)? I just want to make sure the guy I am going to hire to install the wall connector knows this. Thanks!
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