Fire Pump Backup Power Source 695.3

[nhee2]

I rarely deal with fire pump electrical feeds, but am now looking at a one-line for a large process facility. It includes 2 electric 4160 VAC fire pumps. Each are fed by a dedicated 4160 VAC feeder from a common switchgear that also includes a feeder to the balance of plant loads. The switchgear is parallelling gear, fed either from the utility supply, or from two. parallel standby, natural gas generators.

As I review 695.3 I am struggling to see how this would meet many of the requirements there, including 395.3(F) and (G).

Is the configuration I describe a common configuration for larger facilities? Are there exceptions which allow this configuration in other articles and/or NFPA standards such as NFPA 20?

Thanks for any insights

 

[JoeStillman]

I've never done a fire pump at 4160V. It seems to me from 695.3(A)(1) that your feeder in the main gear complies as long as it is connected ahead of the utility main, but I assume that puts you ahead of the paralleling breakers. If the 4160V system feeds a multi-building campus, you would be under 695.3(C).

If it was my design, I would have transfer gear in the pump room (a pair of 5kV breakers), fed from one side (the normal) by a line upstream of the paralleling gear and on the other (the backup) by the line from that gear in your original post. The breakers or fuses in the backup line are not required to carry the locked rotor current, but the normal ones are. Both feeders have to be concrete encased or outside the building everywhere but the switchgear room and the pump room.

Your AHJ may not require the backup feed, but if I was the owner, I would want it. Are the two pumps feeding separate systems, or is one a spare?

 

[nhee2]

I've never done a fire pump at 4160V. It seems to me from 695.3(A)(1) that your feeder in the main gear complies as long as it is connected ahead of the utility main, but I assume that puts you ahead of the paralleling breakers. If the 4160V system feeds a multi-building campus, you would be under 695.3(C).

If it was my design, I would have transfer gear in the pump room (a pair of 5kV breakers), fed from one side (the normal) by a line upstream of the paralleling gear and on the other (the backup) by the line from that gear in your original post. The breakers or fuses in the backup line are not required to carry the locked rotor current, but the normal ones are. Both feeders have to be concrete encased or outside the building everywhere but the switchgear room and the pump room.

Your AHJ may not require the backup feed, but if I was the owner, I would want it. Are the two pumps feeding separate systems, or is one a spare?

Thanks for the reply.
- The Fire Pump feeders are not tapped upstream from the switchgear mains. In fact the switchgear is fed from owner-supplied transformer. Three potential incoming sources - normal utility (via owner transformer), Gen 1 and/or Gen 2. With a single feeder from there to each pump.

I don't think it meets 695.3(A)(1) since it is not ahead of the service connection.

If the AHJ agrees that the service is a 'reliable' service as defined in 695.3 (A) then it might meet the requirements for 695.3(A)(3).

I think it could be considered a multi-building campus style installation - but as I read 695.3(C) it would seem that designing per 695.3(C) would require multiple feeds to the fire pump building, and transfer equipment at that location.

So, I am just trying to understand whether the proposed installation is 'typical' for this type of facility, or (as I suspect) it is not compliant with 695.

 

[nhee2]

Your AHJ may not require the backup feed, but if I was the owner, I would want it. Are the two pumps feeding separate systems, or is one a spare?

The pumps are proposed as 2, 100% capacity pumps, each capable of supplying all required firewater.

 

[JoeStillman]

Maybe skip the transfer gear then and feed one from upstream and one from downstream of the main gear. The transfer gear in the pump room adds complexity that you don't need. I think the AHJ would approve of this application of the KISS rule.