Fire Pump CT and Disconnect size?

[gadfly56]

Not to argue you with you but that is not how the code words it. Also, by not including the full statement you are taking the code out context. But if I am wrong, please explain.

I did a little more digging, and the "assembly listed for fire pump service" isn't necessarily the fire pump controller, but it also isn't something you build yourself. It will be one of these. So, unless you're going to have UL field list your "assembly" you should buy one instead.

 

[scrypps]

This is kind of a funny post because everyone always gets confused about fire pumps. It seems like you could have installed 100 of them but would still need to re-read the code to make sure its correct. I think this diagram is fine. The only criticism is that 1000A is too big for the LRA, the breaker has dials on it so it could be dialed down to 900A, which is the correct amperage (which wouldn't matter since no controller will allow a pump to hit LRA anyway). Also the Jockey pump doesn't need to be sized to its LRA, per NEC.


I don't see a big difference by swapping the design with a 208v motor, if the motor were 208, then the LRA would more than double, which would require a service near 1000A anyways, so basically the added cost here is a 75kva transformer.

Ideally the utility would run straight to a 208V fire pump controller after the CT cabinet, the controller is listed for use as a service, and the code permits it, but many utilities won't allow it since they want a disconnect within site of their meter.

 

[gadfly56]

This is kind of a funny post because everyone always gets confused about fire pumps. It seems like you could have installed 100 of them but would still need to re-read the code to make sure its correct. I think this diagram is fine. The only criticism is that 1000A is too big for the LRA, the breaker has dials on it so it could be dialed down to 900A, which is the correct amperage (which wouldn't matter since no controller will allow a pump to hit LRA anyway). Also the Jockey pump doesn't need to be sized to its LRA, per NEC.


I don't see a big difference by swapping the design with a 208v motor, if the motor were 208, then the LRA would more than double, which would require a service near 1000A anyways, so basically the added cost here is a 75kva transformer.

Ideally the utility would run straight to a 208V fire pump controller after the CT cabinet, the controller is listed for use as a service, and the code permits it, but many utilities won't allow it since they want a disconnect within site of their meter.

If you use an "assembly listed for fire pump service", the breaker cannot be adjustable. You tell the manufacturer the HP and voltage and they send you the correct box.

The jockey pump service needs to carry the locked rotor current per NFPA 20. Remember, the information for LRA are from NFPA 20 NOT the NEC.

Well, if 685 amps is "near 1000" I'll go along with that.