Can someone tell me what the requirements are for a new meter service supplying a fire pump. The pump draws 92A full load at 208V. The only engineering that was done is the main feed of #1 AWG conductors from the utility transformer. It is my understanding that the conductors must be protected by a 125A main breaker. Wouldn't a 200A main panel be sufficient for the load? Why must I supply a 600A rated panel when the main breaker must be 125A? What am I missing here?
Industrial fire pump
- Thread starter eurommk
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ibew501ed
Senior Member
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- danbury ct/work in white plains ny
the fire pump and the wire is rated at 125% of table 430.250
the service is required to be reliable as defined by the ahj and capable of providing 125% of table 430.250. But the ocpd must be sized to carry the current of 430.251b "locked rotor current"
also the wire needs to be sized to limit the voltage drop to 15% at start up
the service is required to be reliable as defined by the ahj and capable of providing 125% of table 430.250. But the ocpd must be sized to carry the current of 430.251b "locked rotor current"
also the wire needs to be sized to limit the voltage drop to 15% at start up
No. This is not correct. As was pointer out "But the ocpd must be sized to carry the current of 430.251b "locked rotor current" The LRA is about 6 x the FLA or 6 x 92 amps = 552 amps. Your can get the LRA from the name plate information on the pump. You overcurrent rating is about 500 amps. The conductor rating is 1.25 x FLA of the motor or 1.25 x 92 = 115 amps. This may seem strange but this applies only to fire pumps. The thinking is that you do not want to interrupt power to the pump and let the building burn down. The pump is to run until destruction.
I have done only one of these, in a coal yard, heavily battery backed up and was not allowed to use so much as a fuse in my panel. The focus seemed more on the physical ramifications of the panel where personnel could not be in the vicinity of the panel in a situation it could explode. It toggles seamlessly from utility to generator back up and is tested once a week by employees dedicated only to it's functionality. And they are highly paid. Think I would rather drive a school bus.
I've never seen a section in the NEC on what I encountered, but remain interested
I've never seen a section in the NEC on what I encountered, but remain interested
This is my first fire pump installation and I must admit that I am a bit puzzled. Do I supply a CT cabinet and tie the 30hp pump and the 3/4hp pump directly to the main lugs without secondary protection or do I provide a secondary distribution panel with breakers sized at 600% of the FLA? The main to the building is rated at 1600A/208V 
I was uncomfortable with my situation. Luckily, the budget allowed me to monitor parameters such as STP on the pump and VAT on the electrics at an HMI, but those were the only methods of protection, which we didn’t employ in the logic, simply used as watch dog parameters.
There were no devices allowed to interrupt.
There were no devices allowed to interrupt.
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