Is #6 NM on a 60A breaker code compliance for a Tesla 48A (continuous load) EV charger?

kwired said:
How easy is it for the user to set it higher afterwards? Guess putting a 50 amp breaker on it does give it a certain amount of limitation but if the max it will draw is 48 amps, you probably won't trip a 50 amp breaker very often or maybe never will at all.
Click to expand...
The NEC describes how secure the setting must be in order to use its value for branch circuit sizing. I believe the Tesla unit meet the requirement.
 
kwired said:
How easy is it for the user to set it higher afterwards? Guess putting a 50 amp breaker on it does give it a certain amount of limitation but if the max it will draw is 48 amps, you probably won't trip a 50 amp breaker very often or maybe never will at all.
Click to expand...
There are some chargers that the end user has access to the settings for max loads from the EVSE, others are part of the electricians commissioning process and the end user has no access. The Tesla's that I've set up had the commissioning by the electricians. I also use ChargePoint, theirs has electrician commissioning for the max setting also. Have had HO that want to buy their own charger units and for most they are owner controlled and for them I wire to the max potential, because inevitably the HO will think "it's not charging fast enough so I'll just set it to the next higher limit"
 
retirede said:
The NEC describes how secure the setting must be in order to use its value for branch circuit sizing. I believe the Tesla unit meet the requirement.
Click to expand...
Fred B said:
There are some chargers that the end user has access to the settings for max loads from the EVSE, others are part of the electricians commissioning process and the end user has no access. The Tesla's that I've set up had the commissioning by the electricians. I also use ChargePoint, theirs has electrician commissioning for the max setting also. Have had HO that want to buy their own charger units and for most they are owner controlled and for them I wire to the max potential, because inevitably the HO will think "it's not charging fast enough so I'll just set it to the next higher limit"
Click to expand...
I have no experience with them is why I asked.

For years I've seen many owners, managers, etc. that will change settings on equipment thinking of end performance but not realizing what the consequences may be. First common one is turning up dial on adjustable motor overloads. With that they don't realize not only does it possibly shorten life of the motor, but the driven equipment likely isn't designed for what they are demanding from it either. An incident I recall one time they burned out a 50 HP motor. Decided why not replace it with a 60 HP. They never considered if the driven load could handle the extra demand on it.

If these parameters are not at least password protected I expect they will get changed once owner finds out the charge rate can be increased. Even passwords end up having ways around them though, worst case - a reset to all default settings and such reset also clears passwords is a likely possibility.
 
kwired said:
I have no experience with them is why I asked.

For years I've seen many owners, managers, etc. that will change settings on equipment thinking of end performance but not realizing what the consequences may be. First common one is turning up dial on adjustable motor overloads. With that they don't realize not only does it possibly shorten life of the motor, but the driven equipment likely isn't designed for what they are demanding from it either. An incident I recall one time they burned out a 50 HP motor. Decided why not replace it with a 60 HP. They never considered if the driven load could handle the extra demand on it.

If these parameters are not at least password protected I expect they will get changed once owner finds out the charge rate can be increased. Even passwords end up having ways around them though, worst case - a reset to all default settings and such reset also clears passwords is a likely possibility.
Click to expand...
Right, nothing is idiot-proof.
 
Hey guys I did not see it mentioned yet, but I installed a Tesla Wall connector generation 3
and the installation instructions that came with it say "If installing for less than maximum power, refer to local electrical code" and the branch circuit has to be copper, so not a big deal to use NM cable.

Then it goes on to say for 'maximum power' the instructions call for " 90°C THWN-2-rated copper wire for conductors" in mandatory language.
It also says "Do NOT install cord-and-plug type connections"
My boss called tesla support and asked if the instructions were part of the listing and they said yes.
 
Why to these EV chargers have to be such a problem? Why do they have to be "on the edge" of Code requirements and material specifications such that an EC has to scratch his head about whether he is doing it right? First, EVERY manufacturer needs to be made to standardize on one design. Then, every charger needs to be hardwired which will eliminate the problem with receptacles burning up. Then a maximum current must be decided on, one that is not able to be changed by the installer or user. If 50A is used, it stays at 50A and the wiring and OCP is installed for 60A.

This shouldn't be any different than installing a dryer or electric range.

-Hal
 
curt swartz said:
For a 48 amp charger?
Click to expand...
Why would anyone have a issue with that , the 60 c ampacity of #6 nm is 55 amps , and 625.42 says evse charging loads shall be considered continuous and 625.41 says the ocpd shall be factored at 125% of the load, so that evse circuit should only be a 40 amp continuous load
40 x 125% =50 amps
The ampacity of a #6 60C conductor is 55 amps
6 nm will never be an issue supplying a 40 amp continuous load
 
Both Tesla and ChargePoint had required CU THHN or THWN-2 wiring in the instruction. So had never consider NM.

Have seen one that was a 15A plug in type the HO had been using, the NM had indication of significant heating up at both ends of the circuit.
 
Fred B said:
Both Tesla and ChargePoint had required CU THHN or THWN-2 wiring in the instruction. So had never consider NM.
Click to expand...
The THWN-2 requirement in the Tesla was by my understanding only if you wanted to use it at the full 48A continuous load.
If you program it to a lower setting such as 40A #6 NM would be allowed, for the Tesla Gen 3 that i installed last week.
I have not run across many Tesla owners whom are short on cash and most are agreeable to a run of conduit across their garage even if its wood framed, and I enjoy bending pipe so tend to look for excuses to do it.
In theory you could get a 55A breaker (or fuse) and program a charger to 44A continuous on #6 NM Its just 50 is not a standard size ? I have seen 55A breakers in older panels and generators
 
retirede said:
The Tesla charger is capable of being deprecated to match the circuit supplying it. In this case, it should be set to 40A and the circuit breaker should be 50A.
Click to expand...
So this is sadly what ended up happening. My friend paid a lot of money to the electrician to be able to charge at the full 48A, but then the electrician skimped on the wires (#6 Romex) and then put in a 50A breaker instead of a 60A breaker. Then he limited the charger to 40A instead of 48A. So 20% of the max charging speed has been lost.

This all could have been avoided had the electrician even discussed these considerations rather than making his own choices regarding installing lower spec wire. My friend would have been happy to pay another $100 to have the 48A he had requested.
 
sunbear said:
So 20% of the max charging speed has been lost.
My friend would have been happy to pay another $100 to have the 48A he had requested.
Click to expand...
Depending on the install your looking at alot more than $100 for conduit vs nm cable.
However unless I am missing something if you want to squeeze every last amp out of #6 NM cant we just factory order a 55A breaker for the panel?
Its not a 'standard size' but Eaton and Siemens both can make them, Generac has a part number for a replacement 55A breaker that I believe is a regular Siemens . I bet HVAC contractors would also buy them if they started showing up at the supply house.

Of course your not at the max so you'd dial the charger to 44A, but that should be close enough?
 
Well if its done I see no reason to leave the 50A breaker there. Swapping a breaker to 55A would be pretty easy.
then unless I am missing something they can charge at 44A continuously.
 
sunbear said:
No need for conduit. The electrician could have pulled 4/3 romex instead of 6/3 and it would have been sufficient for 48 amps charging.
Click to expand...
Still technically a violation though, Tesla only wants THWN-2 if you use the full 48A.
And it does not need a neutral so just 4-2 NM.
 
You must log in or register to reply here.
Top