Two Fire Pump Disconnect switches?

[cvirgil467]

We have an installation where we have a service rated fusible switch in between the utility service and the fire pump controller. The service rated fusible switch is supervised via pad lock in the closed position.

The fire pump controller has a main circuit breaker and a transfer switch integral to the fire pump controller.

Per 695.4-B (2008 NEC), I am allowed a single disconnecting means.

Does the main breaker integral with the fire pump controller count as two disconnect, and therefore I need to remove either the service rated disconnect or remove the main circuit breaker at the fire pump controller?

Thanks
cvirgil

 

[texie]

We have an installation where we have a service rated fusible switch in between the utility service and the fire pump controller. The service rated fusible switch is supervised via pad lock in the closed position.

The fire pump controller has a main circuit breaker and a transfer switch integral to the fire pump controller.

Per 695.4-B (2008 NEC), I am allowed a single disconnecting means.

Does the main breaker integral with the fire pump controller count as two disconnect, and therefore I need to remove either the service rated disconnect or remove the main circuit breaker at the fire pump controller?

Thanks
cvirgil

No! You can't remove anything from the listed controller and you can have both disconnects. But that fusible switch between the POCO and the FP controller will have to be rated to carry the locked rotor current indefinitely. While you did not mention the HP, that usually makes for a very large switch.
I would add that for most garden variety FP installs it would not be typical to have a disconnect between the POCO and the FP controller as all full service FP contrllers are SUSE rated.

 

[gadfly56]

No! You can't remove anything from the listed controller and you can have both disconnects. But that fusible switch between the POCO and the FP controller will have to be rated to carry the locked rotor current indefinitely. While you did not mention the HP, that usually makes for a very large switch.
I would add that for most garden variety FP installs it would not be typical to have a disconnect between the POCO and the FP controller as all full service FP contrllers are SUSE rated.

^^^^^^^
What he said.

 

[cvirgil467]

Thanks to both of you.

FYI - It's a 100 HP motor @ 480v . We have a 800 amp bolted pressure switch fused at 750 amps.

 

[gadfly56]

Thanks to both of you.

FYI - It's a 100 HP motor @ 480v . We have a 800 amp bolted pressure switch fused at 750 amps.

LRC for a 100 HP motor at 480v is 725 per NFPA 20, so you are good to go.