I have a LR RWD Model 3 that states on my display that the max charge amps are 48 A. When my electrician installed my wall connector, he put in a 40A breaker. If I leave things alone, the charger will charge at the full 40 A so I have dropped the max charge amps to 39 A to include a 1A "factor of safety" - I am a little uncomfortable maxing out the circuit. My questions are:
1. Is this worth doing? Or should I just let it max out and charge at the full 40 amps?
2. Should I call the electrician back and ask him to install a 50 A or 60 A breaker so that I can charge at the full amps the car can do? Is there any advantage to charging at the lower rate? I assume my electrician installed the 40 A breaker because that's what he thinks my circuitry can safely handle.
Thanks!
Others have this pretty well covered but I will recap and add some pieces:
This was done wrong. There is no way around that. Even if the wire is good for say 50 amps, by setting the Wall Connector wrong, your electrician has created a situation that will likely result in nuisance trips of the breaker as they are not intended to operate at 100% for extended periods of time.
NEC says that all EVSE’s are “continuous loads” and that you must size the circuit as if the load was 125% of what it actually is (hence people saying the 80% derate which is the inverse of 125%).
The real concern here is that let’s say your electrician only ran say 8 awg romex which is only good to 40 amps (32 amps continuous). Running it at 40 amps continuous takes away that safety margin. I would not do it period.
If you were in a pinch and needed a solution for a day or two I would charge manually at 32 amps using the display screen, but this is *not* a long term solution. As others have stated, you could do the work yourself to tweak the dip switch down by one setting, but I personally would not want to have paid for a wall connector only to get just 32 amps out of it...
The real questions are:
What kind of wire was installed? Romex (NM cable) or something like THHN in conduit? What AWG (size) was it?
Does your “service” (breaker panel) have sufficient ampacity to support a circuit larger than 40a?
What was the agreement with the electrician for? Did they commit to install any particular size circuit? Or was it just to “install the wall connector”? If so, they may have fulfilled their contractual obligations (other than to set the dip switch correctly which is a trivial change).
If I were you, I would optimally want a 60a (or even higher) circuit installed. This is what I have and I love it. My M3 charges so fast!
(though 32 amps may be completely sufficient for your needs)
P.S. Your electrician may need to go back and check any other units they installed this same way. I am not sure how to politely point that out to them.
P.P.S. We are also assuming that the wire is of sufficient ampacity for even 32 amps continuous. We have no evidence of that and very little confidence in your electrican based on the double whammy of only installing a 40a breaker AND setting the dip switch wrong.