NEC Fire Pump Requirements

[mrm]

Typically fire pump circuits are supplied by a tap made ahead of the main disconnecting means in the service equipment [per Article 230-82(5) of the 2008 NEC]. Per NEC Article 695-3(a)(1) the tap is not permitted in the same cabinet, enclosure, or vertical switchboard section as the service disconnecting means. So if the main service is supplied by a 2500kVA, 12470V-480Y/277V transformer (obviously not dedicated to the fire pump circuits) and the tap for the fire pump circuits is made as described above, then the code permits overcurrent protectective devices to be installed ahead of the fire pump circuits in the power supply for either utility or customer-owned supply systems as long as these protective devices are selected or set to carry indefinitely the sum of the locked-rotor current of the fire pump motor(s) and the pressure maintenance pump motor(s) and the full load current of the associated fire pump accessory equipment. See Article 695-4(b)(1) for verification of this requirement. My interpretation of the code is that Article 695-5(b) refers to transformers that are dedicated to the fire pump circuits (primary overcurrent protection only). Please advise if this is the industry accepted interpretation of overcurrent protection for fire pump circuits.

 

[DARUSA]

Where is your transformer inside or outside of the building?

 

[mrm]

In this scenario the 2500kVA service transformer is a padmount located outside the building.

 

[John Paul]

So if the main service is supplied by a 2500kVA, 12470V-480Y/277V transformer (obviously not dedicated to the fire pump circuits)QUOTE]

I have drawings on my desk that show a 1500 KVA, 4150V / 480V Xfmr whose secondary is tapped three times. One is the main switchboard, one is another switchboard, and the third tap feeds four 'Integral Fire Pump controller and Transfer Switch' feeding 200HP pumps. Each IFPTS is fed from the Xfmr above (N - and no protective device) and a generator switchboard (E - with 600A breakers feeding four 200HP pumps). There's a note on the drawings stating that the "instantaneous set above LRA of fire pump".

Does that help at all?

There is a fifth feed direct from the xfmr feeding a ATS for 'building loads'. This is for 480 and 120/208V panels. This feeds alternative source is protected by a 225A breaker.

It's an interesting one line.

 

[dcspector]

My interpretation of the code is that Article 695-5(b) refers to transformers that are dedicated to the fire pump circuits (primary overcurrent protection only). Please advise if this is the industry accepted interpretation of overcurrent protection for fire pump circuits.

Yes.......