Other types of individual 6awg conductors such as THHN or THWN, RUN IN CONDUIT, can be used in circuits up to 65 or 75 amps, depending on the temperature rating you are allowed to use by code or local restrictions.
Other types of wire that can be used at 75c include SE wire and MC cable. Also, for the most part you can't use the 90c rating of wire since I don't know of any residential breakers that are rated at over 75c terminals so the fact that the wire can do more does not really help.
I don’t believe that’s true. On the contrary you MUST downsize to 50A in the case of 6awg romex, not upsize to 60.
So NM wire is limited to the 60c rating which is 55 amps. As mentioned elsewhere in the thread, the Wall Connector only has certain steppings. 40 amps or 48 amps are the relevant ones here. They would require 50 amps or 60 amps of conductor AND breaker ampacity respectively. So you are forced to set the Wall Connector to 40 amps with 6 AWG NM cable.
Now the question is if you can still use a 60 amp breaker even though at the 40 amp setting you only NEED a 50 amp breaker (which is a standard size breaker). 2017 NEC (NFPA 70) 240.4(B) is what defines the "next size up rule". I don't see anything in the rule that says you can only make use of that rule if you NEED it for the intended load.
So while it may be allowed technically, I would not do it normally. I see zero reason to oversize the breaker even more than the 125% rule requires.
It’s much less confusing to use the “circuit breaker” column in the installation manual for the rotary setting.
Yeah, that is probably poorly labeled. It should be labeled as "circuit ampacity" or something like that. "Circuit Breaker" is actually technically WRONG and could be dangerous if someone had sized it using the "next size up" rule.
I understand what you’re saying but it seems ambiguous at best, which is a bummer given my first post in this thread says the NEC is unambiguous on this topic.
This thread seems to be a good representation of thoughts on the topic and is specific to the use case of EVs.
Next size up: conductor size, too? - Mike Holt's Forum
The last post on that thread is salient. I’m 99% positive my local inspector would fail a 60 amp breaker on 6awg NM.
Completely agree RE your point that none of this makes a hill of beans difference with respect to the breaker itself heating up.
Yeah, I actually do think technically a 60a breaker on 6 AWG NM cable is allowed as long as the Wall Connector is set to a 40a max charge rate, but you are right, an inspector might give you a hard time for it. Honestly though, I generally find the inspectors just don't look that closely or know the code well enough to get to that level of detail. Never have I had them look that deeply. EV charging has a lot of very detailed gotcha's with some EVSE's being settable load wise, the 80 / 125% continuous load rule (the fact that they ARE always continuous loads), the next size up breaker rule, derating for ambient temp or number of current carrying conductors, terminal ratings, Article 625.54 GFCI rules, etc... are all very complex and perhaps beyond your average residential inspector.
I believe I'm using normal Romex, 6AWG wire that's not inside conduit except in the actual garage where the line comes down from the ceiling to the sub panel I installed for the wall charger.
I set my rotary dial to #7 which toned the charge rate down to 9kwh from #9 which was charging at 12kwh. I will use my infrared thermometer and take some temp readings.
I will also add this. On top of pretty warm breaker temps while the charger was set
@The #9 setting, my breaker would also have a slight buzzing/humming sound at the breaker for the first 15 minutes or so after I'd plug the charger in my Model 3. The buzzing/humming sound would go away after 15 minutes or so but that still alarms me why it does that.
So warm breakers are OK, hot is not OK. (warm is generally over your body temp to begin with, so I am not sure 115 degrees is actually outside the allowable range?) Note that "standard test conditions" in which they test breakers in (to 100% of their limit) is 40c (104f) in "free air" (so no other breakers up against them). Because they know other breakers will be around them and the temp of the breaker may exceed that, this is the reason the 80% rule comes into play (they only allow you to use 80% of the capacity for continuous loads so that when you go over 104f at the breaker you don't trip it).
Now, optimally though, it would run as cool as possible, that does sound a bit warmer than I would expect. And I don't like the buzzing. Buzzing is common in 60 cycle electrical systems, but it is not super common in residential breaker panels. I would probably inspect the breaker panel carefully (including removing the breaker with the panel powered down) and inspecting the bus bar behind it. I then would likely replace the breaker as they are only $10 or so. It is a cheap attempt at a fix for several issues you have (breaker size, breaker temp, and buzzing).
