Is it ok to hookup a 25A (20A conti) EVSE to 40A breaker?

[ericsf]

Which brand of circuit breakers are you using that will only allow 15 amps continuous on a 20 amp breaker?

Yes, you are correct, I didn't remember the #s correctly. It's 16A continuous.

My point about fuses in appliances was just that IF the wire can't handle the breaker's rating there has to be a fuse. But you're bringing up a good question: Most small appliances do NOT have fuses and they do use 18 wiring. I've looked that up and found some postings of people who wrote that 18AWG cords are safe on 20A breakers. But didn't find a satisfying explanation as of "how".

As you pointed out, ratings depend on many factors. I just looked at the cord of the lamp on my desk: 18AWG - 105C. As far as I can tell, in free air this is rated for 14.4A (18A single in free air - 2 conductors - derating is 0.8). So technically on a 20A breaker this could get submitted to 16A continous and will overheat without tripping the breaker. It would be *missing* 1.6A more capacity to be safe. I'm guessing the rating calculations for appliances have exceptions - maybe on the fact that the length of the cords can't be longer that a certain limits - and that 16A in a 18AWG 2 conductor cord is safe.