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

[Fred B]

(Side note: I learned in this thread that a 55A breaker is a thing. But it's still not a standard ampere rating!)

correct Table 240.6(A) shows 50 or 60 Amp as standard, but wire still must be protected at not more than its max rating. So #6 NM is rated for not more than 55A

Why does Telsa explicitly says to use TWHN-2?

Tesla recognition of the limitation of NM and the equipment requires a 60A overcurrent protection and NM is only good for 55A. Rather than rely on the unskilled deciphering of the code, they bypass this by just dictating the specific wire. THWN-2 gives the 60A under most installation conditions both inside and outside of structures by exceeding the 60A required with a 75A rated conductor. This instruction by Tesla make the installation a 110.3(B) requirement.

 

[pipe_bender]

They go so far as to say what breaker size is needed for the allowable charging settings.

Just like HVAC sets the MOCP / MCA on a nameplate I find that very easy to follow.

So, why isn't Telsa explicitly ok with #4 NM or even #4 AL SER? Why do they care? It is probably just ignorance on their part or maybe just dumbing it down for the uninformed, but who knows.

A Tesla engineer probably went on several electrician internet forums and found many electricians don't use noalox.

Next, when you install an appliance you take a look at the manual to see what it need. I mean that's just standard practice. My nephew just moved into a house and wanted to change some stuff and asked me and I looked at the manual and it need a 30A circuit and we did that. Why is a car charger any different? That's the fault of the person doing the work to properly communicate that there are options and this is what each will cost.

This is the crux of the issue the person in the OP specified the car and the charger, a Tesla, which has a very easy to find manual with detailed instructions for the electrician, they appear to have asked for a bid so they can use it at its maximum 48A setting.

 

[pipe_bender]

Why does Telsa explicitly says to use TWHN-2? That's pretty specific. Once would think they aren't clueless about wire types, but one would also think why do they care except to make sure they account for charing, but following the 125% (80%) rule. They go so far as to say what breaker size is needed for the allowable charging settings. So, why isn't Telsa explicitly ok with #4 NM or even #4 AL SER? Why do they care?

Because NJ and MA are amending their code allowing NM wire with a 60C termination limit on a 75C termination, and liability from insurance claims due to failed terminations (especially failed aluminum) and or melted inferior receptacles.
110.3(B) is their last resort to insure their product is used as they intended, hardwired only and with a copper 75C THWN-2 wire. Or wire how you want (with copper) and adjust it to a appropriate setting for the wire you used.

had the following useful discussion a couple of years back on a similar topic where the conclusion was that #6 NM on a 60A breaker was not code compliant

Tesla charging station

Thanks for everyone's helpful advice so far. Does anyone know any electricians in the Essex County, New Jersey area who would be willing and capable of running conduit through studs? If so, please can you send a direct message to me with the contact details? The electricians I've spoken to so...

forums.mikeholt.com

I was today sent this note from the NJ which comes to the opposite conclusion

https://www.nj.gov/dca/codes/publications/pdf_ccc/CCC_Fall_2023.pdf

 

[curt swartz]

Because NJ and MA are amending their code allowing NM wire with a 60C termination limit on a 75C termination, and liability from insurance claims due to failed terminations (especially failed aluminum) and or melted inferior receptacles.
110.3(B) is their last resort to insure their product is used as they intended, hardwired only and with a copper 75C THWN-2 wire. Or wire how you want (with copper) and adjust it to a appropriate setting for the wire you used.

NM cable has 60C conductors but has not been manufactured in over 40 years. NM-B has 90C conductors. NM-B is not limited to 60C terminations. It can be terminated on 75C terminals. The ampacity of NM-B is still limited to using the 60C column.