Tesla Wall Connector was installed 5 months ago and it's been working great.
Last night the breaker tripped twice within 10 min of charging at 48v.
I lowered it to 40v and it tripped again and the breaker was pretty hot.
This morning I checked/re-tightened the wires connecting to the connector and tried charging and it tripped again.
What could be wrong?...
Thank you
All right, let's take it from the top. You need to do the following checks:
- Open up the breaker box front door and eyeball the breaker. If you're trying to charge at 48A, that breaker has to have "60A" or larger numbers on it.
- Dig out the papers that the electrician left with you. If you're lucky and the electrician's not a fly-by-night, said papers ought to have the wire type and gauge used on the install. If the guy put in the Wrong Size, this could be the problem.
Now for the basics: First off, everything about sizing copper wire and such is About The Heat. Wire has resistance per unit length. Call this Rl; if you put current through a wire, the power dissipated per unit length is Current*Current*Rl, or I^2*R. When power gets dissipated in a wire, it makes the wire get hot, just like the heater elements on an electric stove. Admittedly, unlike a stove, one doesn't want the wire to get red-hot. But the whole business of What Wire Gauge is to make
darn sure the wire in the wall never gets hot enough to singe the insulation. If it
does get that hot, the insulation carbonizes, starts conducting current, and, AND I AM NOT JOKING HERE, it's House Fire City.
So, along these lines, there's the National Electric Code (NEC) which professional electricians ought to have memorized. One of the important rules in the NEC is that if one has a constant heavy load (that's a Tesla, For Sure), then the maximum amount of current of that load cannot exceed 80% of the circuit rating. The circuit rating is the rating of the breaker; the rating of the wire; and the rating of the socket, if any. So, if you want 48A charging current, the circuit rating has to be 60A or greater, since 80% of 60A = 48A. Why that 80%? Because if you
don't do that, the wire will get too hot.
If you told the electrician that you needed 48A and, somehow, said electrician thought that you meant you wanted a 48A
circuit, rather than a 48A
load, said electrician may have put in a 50A breaker (too small!) and 50A wire (also too small!). In which case you're running that breaker Too Darned Close to its rating. Which is why I asked you to eyeball that sucker to see what's printed on it.
There's worse. Almost all breakers operate
thermally; that is, there's a thermostat-like bit of metal in a breaker that heats up and expands as the current increases. When it expands enough, it pops the breaker. But that 80% rule is there in part (and breakers are
designed around that 80% rule) so the breaker never runs near its limit and, therefore, doesn't get hot.
The danger of running a breaker right at its limit like that means that every time one runs full-bore current through the thing that bit of metal inside expands, then contracts when the charging session is over, That flexing on a Really Hot Breaker is just like flexing a paperclip back and forth; eventually, it breaks, just like the filament in an incandescent light bulb.
If you're lucky, it fails the breaker open, so it's obvious that you've got a dead breaker and need a new one. If you're not lucky, it fails
closed, in which case the breaker is no longer a breaker, it's a short. And, Come The Day When You Have A Real Short, said breaker will be on vacation and your house will be smouldering. So one doesn't dick around with the wrong breaker size.
Or the wrong wire size.
If the guy who did the work didn't torque the wires down properly, then things are loose. Loose things have more resistance, cause heat, and Bad Things Happen.
So: Check wire gauge and breaker size and report back ASAP.
We do get reports of dead breakers around here from time to time. As described above, breakers are thermal elements, kind of like light bulbs, and they do wear out with time. But five months is 'way too short for that.
