Hello all! New Leaf owner here :mrgreen: and I've been enjoying my ride for 5 whole days! After much research (thanks to this forum), I've decided to upgrade the stock EVSE using EVSEUpgrade instead of purchasing a dedicated unit. I'll need to install the correct NEMA L6-30R receptacle in my garage but I'm wondering what you all think about what size breaker and what gauge wire to use. I realize I only need a 30A circuit for the EVSEupgrade, but installing a larger capacity circuit would provide a more future proof installation should I decide to get a larger capacity EVSE in the future. There is also the question of 4 vs 3 conductor wire in case I need a neutral at some point. Thoughts?
Opinions about 40A vs 30A house wiring for EVSE installation
- Thread starter Maxstang
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TimLee
Well-known member
See http://www.mynissanleaf.com/viewtopic.php?f=26&t=13158&hilit=+disconnect#p298921" onclick="window.open(this.href);return false; for an in depth discussion of code compliance for a do it yourself installation of an EVSE.
You could have #8 wiring with a neutral installed but only use a 30A breaker and for now ignore the neutral. At a later date a 14-50 outlet could be installed along with a 40A breaker. This is my working setup. I also have a L6-30R on a 30A breaker for test use.
smkettner
Well-known member
If you want to future proof then pull #6 wire. For now stick with L6-30 outlet and two pole 30a breaker to meet code.
If you need 120v pull a separate #12 wire circuit with matching outlet and breaker.
If you need 120v pull a separate #12 wire circuit with matching outlet and breaker.
The #6 wire assumes you have the spare capacity. With my 100A service I could never dedicate half to my car. Really at 80% I have only 80A for continuous loads.
Labor is the most expensive item so you may as well future proof with heavier and added wires.
Labor is the most expensive item so you may as well future proof with heavier and added wires.
mitch672
Well-known member
Maxstang said:
Typically on oversized box would be used, and you'd wire nut the #6 to #10 on the 2 hot conductors for your 30A outet, the ground conductor can be #10 for both the 30A and the 50A, you'd leave the #6 neutral capped with a wire nut.
You can eventually change the outlet to a 14-50 (neutral required by code, but not used by most EV's, including Tesla), and install a 50A breaker. You'd then be set to charge a Model S (or future Gen3) at 40Amps.
TonyWilliams
Well-known member
GlennD said:
A NEMA 14-50R outlet requires a 50 amp breaker.
wwhitney
Well-known member
Short answer: the NEC allows NEMA 14-50 receptacles on a 40 amp circuit. This is because there are no NEMA 14-40 receptacles.TonyWilliams said:
[BTW, for this reason I find it dubious that that Tesla UMC defaults to 40 amps continuous when fit with the 14-50 plug. They really should have a way to select 40 amps or 32 amps when using the 14-50 plug.]
Longer answer: on a 40 amp or 50 amp multi-outlet branch circuit, every receptacle has to be rated for 50 amps (since there are no 40 amp receptacles). On an individual branch circuit (only one outlet), the only requirement is that the receptacle rating is not less than the branch circuit rating. So you could put a 14-50 on a 20 amp branch circuit, although typically that wouldn't be very practical.
Cheers, Wayne
smkettner
Well-known member
You can pigtail the #6 with some #10 for the last 3" to 6".Maxstang said:
eHelmholtz
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To add to this, when my Blink unit was installed, it had a 6-50 plug and the circuit was 40A, meaning that the max EVSE output should be 32A. This is why I find the UMC adapters problematic. I solved it by building an adjustable current openEVSE for a fraction of the price of the UMC that I converted.wwhitney said:
TonyWilliams
Well-known member
wwhitney said:
Another case of following made up rules to the detriment of safety.
The rule is dumb. A 50 amp receptacles needs a 50 amp breaker and wires capable of 50 amps... I don't really care what a flawed, obviously unsafe rule "allow".
wwhitney
Well-known member
But if you have a 30 or 32 amp EVSE, its manual probably calls for a 40 amp breaker. If you want to cord-and-plug connect it, you need to use a 50 amp receptacle on a 40 amp breaker.TonyWilliams said:
Cheers, Wayne
TonyWilliams
Well-known member
wwhitney said:
And yet another flaw in the "official" rules. There should be a 40 amp plug.
Tony, sometime in the past it was decided that since there was no 40A receptacles then you could use 50A ones with the proper breaker for the wire. In building EVSEs I have found you can purchase 40A range cables with #8 wire and 50A ones with #6 wire.
At this late a time it is not going to change. It is OK to not like it but that is not going to change anything.
At this late a time it is not going to change. It is OK to not like it but that is not going to change anything.
TonyWilliams said:
theds
Well-known member
TonyWilliams said:
Don't understand your logic. The breaker should be rated less than the wire and the receptacle greater than the breaker. And it's perfectly safe.
mitch672
Well-known member
The Assumption is that a 14-50, 50A outlet can be used as such, unless it is labeled as "40A MAX"
If you plug in a Tesla UMC, and you don't turn down the charging current to 32A in the car, you will blow the breaker due to overheating. Worse, if you can't get to the panel, you won't be able to reset the breaker (think commercial installation, not residential)
If you plug in a Tesla UMC, and you don't turn down the charging current to 32A in the car, you will blow the breaker due to overheating. Worse, if you can't get to the panel, you won't be able to reset the breaker (think commercial installation, not residential)
theds
Well-known member
It may be inconvenient, but it is still safe.
mitch672 said:
LTLFTcomposite
Well-known member
If you put a continuous 40a load on a 40a circuit with #8 wire will it overheat the wire and/or trip the breaker or is it just that there is no cushion if the breaker is a little weak?