I had a licensed/bonded electrician install the 6-50 nema 6-50 plug on a 2 wire 30amp line over 10/3 cable. When testing the car, I told him I was getting 32amps, he said it was no problem. Wouldn’t trip the breaker, 10/3 can handle it and it wouldn’t damage the car.
He was right, the car is fine, and I’ve never tripped the breaker. Am I missing something?
Yeah. The electrician's an idiot.
So, it's not immediately clear from your post, but I'm presuming that the duplex breaker in the breaker box is a 30A model. Under a steady load, those are supposed to trip at 30A, plus or minus an amp or two.
Thing is, nearly all breakers use
thermal elements to trip. Some or all of the current in the breaker goes through that thermal element, causing it to heat and expand. At some point, it'll pop. There are hard limits: For example, at 2X the rated current, there will be some maximum and minimum time for the breaker to pop. At 4X those times will be
much shorter.
But what this does mean is that you're
flexing the thermal element when you run a 30A breaker at 32A. This leads to metal fatigue.
Now, if you're
lucky, when (not if) the breaker fails, it'll fail open. If you're not lucky, it'll fail short. And then you don't have a safety leg to stand on when there
is a short. This is how houses get burnt to the ground.
A breaker is a safety device and not to be trifled with.
There's more. Let me check the current ratings on 10/3 cable... Found this
link. Not sure, but depending upon the cable, that cable's good for 30A to 40A, depending, and I don't know which one you've got.
Thing is, the 10Gauge wire sits in the cable. The wire is surrounded by plastic kind of resists the flow of heat from the power dissipated in the copper wire (I*I*R). The cable itself is surrounded by even more insulation, dry wall, wood, and all that. The more
thermal resistance there is between the copper and the ambient, the hotter the wire is going to get. So, the question is, given the thermal resistivity of all those different kinds of insulation, Just How Hot Is That Wire Going To Get? There are
reasons they wires have ampacity limits, and they all have to do with the copper getting hot enough to singe things and set the Darn House On Fire.
NEC says: The breaker, the wire, and the socket should all match. There's one exception of which I'm aware: One is allowed to put a 50A socket on a 40A line, with a 40A breaker, to handle things like clothes driers and electric stoves that present a 40A load.
You are running a 30A breaker and 30A wire on a 50A load and are so far out of code you can't see it from here. There's more: The National Electric Code (NEC) states that, with a heavy, steady load, one is not supposed to run more than 80% of the maximum current for the circuit. With 30A wire, 30A breaker, that would be 24A.
And your electrician is an idiot. And maybe trying to kill you. Did you offend him somehow?
Did the electrician give you his/her
real name, and a
real phone number? Or are they just hoping that Nobody Finds Out before they move to Florida?