FIre Pumps, CT Cabinets and Generators

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jjs

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Puryear, TN, USA
After reading through 5 pages of fire pump threads I could find on this forum, I still have a couple questions. I was able to get enough info to answer most of my questions, but I am posting my conclusions here so that someone can tell me if I made any mistakes based on what I learned from the forums and through reading the code. Thanks in advance.

I have a 208V, 3P 75HP fire pump. The utility was declared not reliable by the AHJ, so we have a NG genset for backup located outside.
The motor for the fire pump is a Baldor FPM2549T-2/4 SCI Ball Brg UL Listed, Class Insulation TYpe: Cls F Ins 40 Deg Amb 1.15 service factor http://www.baldor.com/mvc/DownloadCenter/Files/FL441

The nameplate FLA of the motor is 192.8 and LRA with ATL starter is 1170A. The NEC FLC is 211A. The NEC LRC for a 208V 75HP is 1200A.

The generator was sized based on using a Wye/Delta starter. The LRA for wye/delta should be ??????

The generator software provided a 230KW generator to supply the fire pump, which is the only load on the generator.
Normally this generator would get an 800A CB output. According to 2011 NEC 695.4(B)(2)(b) it seems i use 430.62 for sizing the CB for SC protection only. 430.62 refers to table 430.52 which sets the maximum rating for an inverse time breaker at 250% of FLC = 211*2.5 = 528A, so a 600A CB could be used. Is this correct?

What is the smallest CB that could be used? Is it 126% FLC? Assuming it actually starts the motor without tripping.

The feeders from the generator shall be sized based on 695.6(B)(2) which refers to 430.22 and VD requirements of 695.7 which requires no more than 15% voltage drop during starting and no more than 5% VD during running at 115% FLC
430.22 requires conductors be rated 125% of motor FLC = 264A which means 300 kcmil minimum.
For the 695.7(A) starting voltage drop calculations, if I plug in 1200A for LRC and 200’ of length, at 0.8PF I get 13.55%VD using 300KCMIL CU in RGS
For the 695.7(B) running voltage drop calculations, if I plug in 211A *1.15% for FLC and 200’ of length, at 0.8PF I get 2.74%VD using 300KCMIL CU in RGS
Fire Pump Controller can handle (1)#3-350MCM PER Ø

Feeder from utility transformer would also be 125% FLC so would also be 300kcmil. The generator and utility transformer are similar distances to the fire pump.

The utility requires a CT cabinet and meter for the fire pump. Do I size the CT cabinet on the 125% of FLC? Or LRC? Is there a direct code section I could cite for this?

Also, it is my understanding that the pressure maintenance pump (jockey pump) does not need to be backed up by the generator according to NFPA 20 4.25.8 “The pressure maintenance pump shall not be required to have secondary or standby power.” Any exceptions to this that would require me to put it on the generator?

The generator is located outside in a manufacturer’s enclosure. It is in a northern climate and requires some heaters and a battery charger. Do any of these auxiliary items need to be backed up by generator power?

Did I make any mistakes?
Thanks for your help.

JJS
I have not posted in a while, but I really appreciate the knowledge of all the people that answer.
 
1. Are the heaters required once the generator is running?
2. Will the generator ignition and controls keep running indefinitely without a battery charger? I.e. is there an alternator to supply the ignition (if any) and maintain the battery for restarting?
The answer to those questions should tell you whether the mains powered charger needs to transfer to the generator output (or have a second unit driven directly from generator output.)

Sent from my XT1585 using Tapatalk
 
Several things to consider

Starting power factor would be around 40%.

Many AHJs do not consider natural gas to be reliable, and require propane backup.

The CTs should be based on running current, not starting. It isn't covered by NEC.
 

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dkidd said:
Several things to consider

Starting power factor would be around 40%.

Many AHJs do not consider natural gas to be reliable, and require propane backup.

The CTs should be based on running current, not starting. It isn't covered by NEC.
Click to expand...


So do I use the 1200A starting current and the 40%PF? If I run it with those values for 200' of length the 300kcmil still work, the VD software program gives about 13.00% VD
So it will still work with 300's which is good.

So I think the only question remaining is whether the auxiliary items require backup. I will ask the generator rep about the alternator and report back what I hear.

Thanks.
 
Generator spec lists a battery charging alternator under the "Engine Electrical System" section.

so it is really just the heaters I think. The genset should start as soon as power is lost, so the heaters should have been working to that point, and the engine should keep itself warm once running.
 
I'm working on a project similar to this and I don't understand the requirements of 695.3(A). If none of the available power sources (utility, standby generator, etc.) are capable of carrying indefinitely the locked-rotor current of the fire pump motor, is the installation in violation of the NEC? I'm adding a 75hp, 208V fire pump to a warehouse currently served by a 75kVA, 208V utility transformer. Do I need to ask the utility to upsize the service transformer to 500kVA? I realize the NEC does not have jurisdiction over utility equipment, so this one really has me stumped.
 
jjs said:
So do I use the 1200A starting current and the 40%PF? If I run it with those values for 200' of length the 300kcmil still work, the VD software program gives about 13.00% VD
So it will still work with 300's which is good.

So I think the only question remaining is whether the auxiliary items require backup. I will ask the generator rep about the alternator and report back what I hear.

Thanks.
Click to expand...

Still looking through 695, but for sizing the generator 695.3(D)(1) says (emphasis added):

(1) Capacity. The generator shall have sufficient capacity
to allow normal starting and running of the motor(s) driving
the fire pump(s) while supplying all other simultaneously
operated load(s). [20:9.6.1.1]


Automatic shedding of one or more optional standby
loads in order to comply with this capacity requirement
shall be permitted.

So, you shouldn't have to use the 1200 amps to size the generator.

While the AHJ may be OK with an NG fired generator, NFPA 20-2013 may not:

9.6.2.3 The generator fuel supply capacity shall be sufficient
to provide 8 hours of fire pump operation at 100 percent of
the rated pump capacity in addition to the supply required for
other demands.

To me that means you need on site storage. See what the fire subcode official has to say.
 
Fire Pump ATS locations

Fire Pump ATS locations

I know NFPA 20: 9.6.4 says "shall" take place with in the pump room. Is there any exceptions where the fire pump ATS can be outside with only (1) feeder coming in? Very difficult to bring in (2) encased feeders.

Job notes:
Existing bldg:
Fire Pump is in electric room with controller
75 HP = 5 hp booster pump
Fire pump feeder will be moved to the utility xfrmr

Thanks
 
jneeld said:
I know NFPA 20: 9.6.4 says "shall" take place with in the pump room. Is there any exceptions where the fire pump ATS can be outside with only (1) feeder coming in? Very difficult to bring in (2) encased feeders.

Job notes:
Existing bldg:
Fire Pump is in electric room with controller
75 HP = 5 hp booster pump
Fire pump feeder will be moved to the utility xfrmr

Thanks
Click to expand...

I don't know of any exceptions that would ease your pain.

I'd say discuss it with the AHJ. You'll need buy-in from at least the fire sub-code and the electrical sub-code, and the building official will have the final say. In my experience, AHJ's don't generally view "very difficult" as grounds for waiving a requirement. YMMV.

P.S. Don't forget that the whole "2 hour fire rated assembly" who-ha stops at the boundary of the fire pump room. Once inside the room, normal wiring methods are allowed, with some restrictions (has to be in RMC or MC?). Does that help?
 
jjs said:
The genset should start as soon as power is lost, so the heaters should have been working to that point, and the engine should keep itself warm once running.
Click to expand...

Any reason not to run optional standby loads (as permitted), too? Seems like a waste to have the generator spinning, unloaded, on the far-off chance that the fire pump is needed.
 
jneeld said:
I know NFPA 20: 9.6.4 says "shall" take place with in the pump room. Is there any exceptions where the fire pump ATS can be outside with only (1) feeder coming in? Very difficult to bring in (2) encased feeders.

Job notes:
Existing bldg:
Fire Pump is in electric room with controller
75 HP = 5 hp booster pump
Fire pump feeder will be moved to the utility xfrmr

Thanks
Click to expand...

I'm confused. Is this an older existing installation that is being modified? The pump is in the "electric" room? This has not been allowed for years. Same with controller and ATS-must be in the fire pump room. Also,while technically code possible, as a practical matter the controller and ATS are 1 factory built and listed unit. An ATS used with a fire pump system can't be just any listed ATS, it must be listed for fire pump service.
 
texie said:
I'm confused. Is this an older existing installation that is being modified? The pump is in the "electric" room? This has not been allowed for years. Same with controller and ATS-must be in the fire pump room. Also,while technically code possible, as a practical matter the controller and ATS are 1 factory built and listed unit. An ATS used with a fire pump system can't be just any listed ATS, it must be listed for fire pump service.
Click to expand...

Where are fire pumps not allowed in "electric rooms"? As long as everybody plays nice on clearances where's the code restriction?
 
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