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How do you size a circuit breaker for a fire pump to comply with NEC requirements?

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Per the NEC 695.4(B), a fire pump breaker has to be sized so that it provides short-circuit protection only. This requires it to be sized so that locked rotor current will not trip it, and that means it must be sized at about 6x the FLA. 
The circuit breaker protecting a fire pump circuit must have a current rating above the fire-pump motor's locked rotor current.  
For example, a motor with a FLA of 124 would typically have a locked rotor current of 6 x 124A = 744A; so we would recommend an 800A breaker such as PJL36080U31A.

A common misunderstanding is that “short-circuit protection only” means “instantaneous trip circuit breaker.” This drives an incorrect specification for equipment and results it an NEC compliance issue.  Instantaneous-only devices are Recognized Components (Not Listed); they have no marked short-circuit rating and are not (by themselves) suitable for branch circuit protection.

Please see attachment for more explanation.
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