Since the CB is protecting the wiring, not the device, if the WIRING is sized for 50A, you could install a 50A breaker, but that would allow a maximum of a 40A EVSE to be placed on it.
When designed, a device does not generally rely on the CB at the panel for its protection...if there is some required internally, they'll install a fuse or other protection IN it...again, the CB at the panel is to prevent the wiring going TO the device is not overloaded and potentially overheat and burn in behind walls, etc. There may be exceptions where the installation instructions call for it to be a dedicated circuit for the device, though. When you put a plug on the wall, it's always best to ensure that the wiring can handle anything designed to plug into that receptacle. For whatever reason, though, the 'dryer plug' is on exception to the rule, but then, someone may buy a new one that needs more power and not know the wiring won't support it.
Last edited by jadnashuanh
on Thu May 10, 2018 11:46 am, edited 1 time in total.
2014 i3 BEV, 2021 X5 45e
(The i3 will be sold soon, <17K-miles, interested?)