240.3 tells us to use table 240.3 for overcurrent protection of equipment as specified by it's article in the table...
440.6(A) guides us on how to do this...
Use 440.32 or 440.33 to size branch circuit conductors...
example: (440.32): 20.8 RLA x 125% = 26amps
Then table 310.16 75 degree terminals require #10 copper
Then go to 440.22 for breaker or fuse size...
example: 20.8 amps x 175% = 36.4amps
So this manufacturer went with the 40amp Breaker because your allowed up to 225% per 440.22.
Hope this helps. Think I nailed it.
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