Full disclosure: Article 695 is not my friend.

[charlie b]

(My computer is so archaic that I have no way to turn the attached image right side up. Sigh!)

This building is in final stages of commissioning. The switchboard is installed and energized. Panel FPP feeds two fire pumps, one jockey pump, and two hangar bay doors. It gets its power from upstream of the main breaker, but apparently not in a separate vertical section. Also, a 100 amp feeder breaker would not hold indefinitely with locked rotor current from even one of the fire pumps, let alone both. I gather that since these pumps supplied expanding foam, and not fire water, they weren’t initially treated under article 695. I need to find a solution.

Here is what I hope can be done:

• Move the 100 amp feeder breaker into the vertical section that shows the SPD. If necessary, move the SPD to the vertical section that presently shows the breaker.
• Replace the 100 amp breaker with one that can handle locked rotor current from two fire pumps. Unless I can pin down the exact motor and its catalog data, I have to use 21 amp full load, times two motors, times 6, or 246 amps. I would use a 250 amp breaker.
• I believe I can leave the conductor sized for about 60 amps (2 motors at 21 amps, one of those with 25% extra, and one motor at 11 amps). I don’t have to size the feeder for the entire 250 amps. Is that right?
• I will also move the two hangar bay doors to another panel, to get them away from the fire pumps.
• The breakers on FPP that serve the two fire pumps are 35 amps. Do they also have to handle locked rotor current for their individual motor?

Do I have to abandon this scheme, and try to find a way to get the fire pumps each connected to a separate breaker upstream of the main and on a different vertical section than the main?

 

[LIM]

I don't have a copy of 2017 so I am basing this on 2014---------I am sorting through your situation but one piece that stands out is the locked rotor current is only based on the largest motor plus the jockey pumps. You wouldn't have to include both fire pumps LRC the way I read this section. This value also does not apply to conductor sizing as you have mentioned.

 

[charlie b]

Thanks, LIM. But I will have to disagree. NEC 695.3(A) says that the power source has to be "capable of carrying 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." That is in 2017, but is not indicated as being a revision from 2014. Even so, that only impacts the degree of the problem, not the nature of the problem.

 

[texie]

Charlie,
A few questions/comments:
1) I don't think you can have that panel FPP. Both FP controllers would have to be fed separately from a tap ahead of the service. This is because only 1 disconnect can be between the source and the controller except in a campus setting as allowed in 695.3(C). See 695.4(B).
2) How is the supply wiring getting from the source to the FP controller? Is it fire rated?
3) Are the pumps/controllers in an NFPA 20 compliant room?
4) Maybe consider running each controller back separately directly to the POCO transformer as service conductors and not use any OCPD. The controllers are SUSE, right? They are listed FP controllers? Or use OCPD's located outside and set for locked rotor and use circuit integrity system to get to the controllers. My point is the wiring has to be protected thru the building to the fire pump room either as service conductors or a listed system.

 

[charlie b]

I will be visiting the site later today. I will see how the conductors are routed.

Follow up question: The 20 amp breaker upstream of the main breaker feeds a transformer, which in turn supplies the fire alarm system. Does this comply with 230.82(5)? Specifically, that article says, ". . . if provided with service equipment. . . ." Since the first thing downstream of the 20 amp breaker is not "service equipment," but rather is a transformer, is this installation legal?

 

[steve66]

I will be visiting the site later today. I will see how the conductors are routed.

Follow up question: The 20 amp breaker upstream of the main breaker feeds a transformer, which in turn supplies the fire alarm system. Does this comply with 230.82(5)? Specifically, that article says, ". . . if provided with service equipment. . . ." Since the first thing downstream of the 20 amp breaker is not "service equipment," but rather is a transformer, is this installation legal?

I don't think that section (230.82) applies, since its off a 20A breaker. The breaker is one of the 6 allowed service disconnects, so I don't see a problem with it.

I think 230.82 only applies it you tap of the service without a disconnect or OCP and then run to something with its own service rated disconnect and OCP (like a service rated surge suppressor).

 

[charlie b]

Thanks for the assistance. I visited the site yesterday and met with the GC and EC. The path forward is to tap the switchboard bus upstream of the main breaker, and run new conductors to the fire pump controllers. There will be no OCPD at the tap point. The tap point will be in a separate vertical section from the main breaker and the feeder breakers. The electric room and fire pump room are adjacent. So there is no need to put a fire barrier over the conduit.