Power Source for Fire Pumps
Power Source for Fire Pumps
(OP)
I'm designing for 3-100HP electric fire pumps. Per NFPA 409 two of the pumps are to be adequate for the system demand with the 3rd pump as a standby. It's my interpretation that the transformer would be sized for 125% of the full load of two of the pumps, not three.(NEC 695.5(A)) The pumps are controlled by pressure. It takes two pumps to maintain the required pressure. I guess it's conceivable that a leak in the system could cause enough pressure drop during a fire so that the 3rd pump would come on, in which case I can see the need to include all pumps in the sizing.
A similar question arises with the Overcurrent Protection (NEC 695.5(B), which is to be sized to carry the locked rotor current of the "fire pump motor(s)". It's not likely, but it's not impossible for all three motors to be in locked rotor condition, which would lead me to include all three motors in the selection of rating.
I would appreciate comments.
A similar question arises with the Overcurrent Protection (NEC 695.5(B), which is to be sized to carry the locked rotor current of the "fire pump motor(s)". It's not likely, but it's not impossible for all three motors to be in locked rotor condition, which would lead me to include all three motors in the selection of rating.
I would appreciate comments.





RE: Power Source for Fire Pumps
That probably also mean the ability to handle simultaneous locked rotor current of all three pumps indefinitely without tripping.
You could always make one engine-driven instead of electric.
RE: Power Source for Fire Pumps
As dpc suggested, you should have at least one engine-driven; probably two. If one pump is engine-driven, the other two electric pumps should be powered by both a emergency and the main power sources.
Best of luck.
RE: Power Source for Fire Pumps