fire pump inquiries

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vincedigital

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Location
caribbean
Occupation
electrical cad technician
can i have a fire pump panel (120/208v 3phase) with the following loads; or fire pump needs to be directly fed from the utility company?
- fire pump, jockey pump, fire pump and jockey pump controller, light and receptacle in fire pump room
if the fire pump is 50hp and looking at table 430.251 (B) it says 802 amp on a 208v 3phase service. is there a 850amp breaker? or i can get away with 800amps?
 

don_resqcapt19

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Location
Illinois
Occupation
retired electrician
The fire pump and the jockey pump can be on the same feeder, but that needs to originate from a separate service or from a isolated compartment in the service switchgear. This circuit is not permitted to supply lights and receptacles.

You can't use Table 430.251 to get the locked rotor current for a fire pump. Per the heading of the table, the table is only for use only with 430.110, 440.12, 440.41, and 455.8(C).

You need to find the locked rotor code indicating letter on the motor and apply Table 430.7(B).

695.4(B)(2)(a)(1) says: " Where the locked-rotor current value does not correspond to a standard overcurrent device size, the next standard overcurrent device size shall be used in accordance with 240.6. "

A locked rotor current of 802 amps would require a 1000 amp OCPD.
 
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