Fire Pump Main Service

[Tcwaggs]

I am hooking up a fire pump on a project. It has it's own service. The main fire pump and the jockey pump are the only 2 things this service is for. I do not have a main disconnect installed, rather each pump has it's own service rated disconnect. I have a wireway installed to tap the service entrance conductors.

The fire pump controller has a 150 amp service rated main breaker installed because it has to be sized 600 percent above the LRA of the pump which I understand. I have # 10 wire feeding the pump because the RLA is only 23.7 amps.

The jockey pump is is tiny, less than an amp, so I have a service rated disconnect with fuses feeding the jockey pump.

The ampacity of the entire load calculated at 100 percent of the LRA of the main fire pump and the jockey pump is less than 40 amps, so I have # 8 copper wire for service entrance conductors (that enter the wireway from the transformer). The inspector is telling me that the service entrance conductors have to be rated for the 150 amp disconnect in the fire pump controller, hence making them 2/0 copper conductors. I disagree with the inspector because this is a fire pump service, not a typical service.

Am I wrong?

 

[tom baker]

The fp controller internal 150 A disconnect is sized to interrupt short circuit current to the motor
Size your service conductors base on 125% from the motor HP table + 100% of jockey load, and limit voltage drop to 3% per art 695
Fire pumps modify the rules in article 230, for a reference please see section 90.3

 

[Tcwaggs]

Thanks for the reply Tom. So, calculating the service conductors that way gives almost the same results. It is still less than 40 amps. So, my service entrance conductors can still be # 8 copper, correct? I'm just wondering if a main service disconnect is required for this application. I don't think it is required because I have less than 6 disconnects (2 to be exact) and they are both service rated.

The inspector is adamite about using service entrance conductors rated for 150 amps. He's wrong, but how do I get him to approve this service?