electric supply to fire water pump 1

[jacphi]

i have a controlgear rated for 1200A,480v. one of the feeder is a fire water pump.having a FLA of 240A(locked rotor current 1500A Approx. i am extracting the local std requirement for fire pump unit package.
"QUOTE"
The protection schemes for Fire Pump Unit (FPU) packages shall comply with NFPA 20 and NFPA 70. In general, these standards require that the motor be allowed to operate under locked rotor condition continuously and is only automatically disconnected under short-circuit conditions.
Exception :
The exception to these requirements is that where a FPU package is fed from a bus that has ground overcurrent protection on the incomers or supply transformers, the feeder to the FPU package shall have ground overcurrent protection, and all other feeders connected to the same buses or transformers shall have ground overcurrent protection.
"UNQUOTE"

my question is will this controlgear be sufficient to supply the locked rotor condition mentioned? does the exception above mean that by providing groung fault protection i do not have to comply with require that the motor be allowed to operate under locked rotor condition continuously. please comment.

 

[Sparkyonline]

No. The exception deal with the disconnecting portion of overcurrent protection. In other words, if you have the ground fault protection, you are 1) required to have it present at all the locations listed, and 2) now allowed to have the ground fault protection automatically disconnect in the ground fault instance and not only in the short-circuit instance.

With this requirement, the locked rotor "operation" could easily exceed the capabilities of the gear in question, even without considering the other loads involved.

Consideration should also be given to emergency requirements for this service.

Also, some locations will allow you to have separate service for the fire pump and associated equipment.

Hope this helps.