The 80% derating only applies to 'continuous loads' which are defined by NEC to be anything >3 hours continuously at maximum current. Any circuit breaker will

The 80% derating only applies to 'continuous loads' which are defined by NEC to be anything >3 hours continuously at maximum current. Any circuit breaker will not trip at the rated current, though. They're designed not to. So, you can run all 48kW indefinitely without tripping a circuit breaker, assuming everything else is sized appropriately (i.e., wire, interconnects, etc).