EVDRIVER wrote: It is very common for people to move and have a Tesla plugged into a 14-50. That means you are drawing 40A on a 40A breaker which is more than the 80% rule. Since most 40A breakers are not rated for continuous use as the connectors on that type of breaker are designed so they do not come loose. Ones that do then create high resistance and then potential big issues. I have seen this heat related failure on more than one overloaded breaker.
To clarify this, there are two separate issues with using a 40A breaker at 40A continuously:
1) With a 40A continuous load, all the connections in the circuit are going to be put to the test. Any poor connections are going to quickly develop hot spots, and if not caught could start a fire. The same is true of a 32A continuous load on the circuit, but only 64% as much power would be dissipated at the poor connections. That would still be enough to cause most poor connections to show up, but obviously there could be a marginal connection that survives 32A but not 40A.
2) For a 40A breaker in the worst case environment (40C ambient temperature, in a panel full of other breakers), the thermal trip is only designed to hold at 32A continuously (80%). If the continuous current exceeds 32A, the thermal trip mechanism may trip. That thermal trip mechanism is the only part of the circuit that is not rated for 40A continuous.
Because of (2), when installing a 40A continuous load, it is necessary to specify a 50A breaker. And because the wiring needs to be adequately protected by the breaker, the wiring needs to be rated at 50A. The result will be a circuit in which everything is rated for 50A continuously, except the thermal trip rating of the breaker, which will be rated to hold at 40A continuous.
It is a poor product design choice that the Tesla Mobile Connector doesn't offer an option to plug into a 14-50 receptacle while restricting the EVSE current to the 32A maximum suitable for a 40A circuit.