the Branch Circuit Breaker may be sized to be Maximum 250% the FLA.
This is not true if the end use equipment is not a single motor and most 'packaged' units are not. 450.52 only applies to single motor circuits, I only mention this because I've seen this section applied to the wrong equipment too many times.
To further complicate things some engineers and AHJ's will view the circuit from the disconnect to the mechanical unit as a 'motor' feeder, but not the circuit from the circuit breaker to the disconnect and they will size or require the circuit between the breaker and switch to be sized per the breaker size, 110A (#2's) or 150A (1/0's) in the event it's a single motor device).
If you use an un-fused switch at the equipment then the breaker can be no larger than 110A (per the equipment label) and the feeder between the breaker can remain #4's (for a single motor).
