I have received a few quotes to install my Tesla Wall Connector for my model 3. The biggest difference between the quotes is wire size. All electricians have their reasons, i’d like to know what you think
My setup:
60A circuit breaker
48A max charging amps (wall connector setting #9)
35 ft. From breaker box to connector location
Wire Ampacity Ratings
6/3 Romex = 55A
4/3 Romex = 70A
Contractor #1
6/3 Romex
NEC 240.4(B) exception allows rounding to next highest breaker size if wire ampacity is in between breaker sizes.
Contractor #2
4/3 Romex
+$220 more expensive
As a side note, what wire size are you running to your Tesla Wall Connector (HPWC)? Also I am doing the 3 wire so I can replace my HPWC with a NEMA 14-50 when I move.
Contractor #1 is proposing something that violates electrical code. They are correct in that you would be allowed to use a 60a breaker on 6/3 NM cable (Romex), but you still have to make sure the load you are attaching to that circuit is 55 amps or less (or in the case of a continuous load, 80% of 55 amps which is 44 amps). EVSE's (like the HPWC) are always considered continuous loads per NEC.
Contractor #2 is proposing a valid solution, though if using 4 AWG Romex you could even install a 70a breaker and give yourself a little more power if you ever plugged in a different vehicle that could make use of it (assuming your load calcs allow this much capacity on your service/feeder/panel).
Other valid options would be 6 AWG in conduit which allows using the 75c rating which allows 65 amps. This is what I did. 60a breaker, 48a usable for my Model 3 LR.
I use THHN/THWN copper ...for your setup u can get by with 6...4 is better but the contractor is gouging u on material go Home Depot buy yourself from bulk roll
Yes, #6 AWG THHN/THWN is fine as stated, but it must be installed in conduit. If Romex works better for this application then #4 is required.
I also find it interesting that I read on the forum the conductor size for the HPWC 25' cable is #8.
The cable from the HPWC to the car falls under totally different rating systems. First off, it is more of a UL issue than a NEC issue I think since it is part of an appliance rather than permanently installed wiring (though the NEC does have code around it, so I am not 100% sure to be honest). But that cable is generally rated for pretty high temperatures, and most importantly, it is not installed in walls - it generally hangs in free air and so it can let off heat easier.
I agree go #4 ...however if you go out and buy #4 cost differential is approx 1.25/ft so for 35ft run I don’t see how his contractor is quoting 220 more
#4 is probably a lot more of a pain in the ass to deal with through walls, studs, etc... This is likely not something they "keep on the truck" so they may be sandbagging a bit to cover needing to buy a spool. #6 is probably a lot more common.
Go 6/3 and use 50 Amp breaker and 40A HPWC setting. Yields full charge in 8 hours (only 7 mph lower rate than 48 Amp).
The electrician may not be aware that EV charging is concidered continuous loads, not intermittent.
If you charge at 48A, the circuit needs to be rated for 125% of that or 60 Amps, which exceeds 6 AWG NM-B at 60 C.
Is #6 Romex ok on a 60 A breaker
I personally would want to be able to charge at the full 48a (requiring a 60a branch circuit and breaker), but to each their own. My car charges from my daily commute in about an hour at 48a which is crazy fast. I could get away with a much slower charger, but if already spending the money on an HPWC and electrician, paying for the slightly larger wire makes sense to me.
@SDRick ...#8 is too small ...maybe for the ground
..but not for the hots
#8 THHN in conduit would be fine up to 50a (40a continuous which is what the car needs). I would probably recommend at least #6, but #8 on a 50a breaker, run in conduit, and with the HPWC set to position eight, 40a would be completely safe and code compliant.
