Fire Pump Starting
Fire Pump Starting
(OP)
I have to start a 100HP fire pump motor; the maximum allowed voltage drop at motor starting is 15%.
Can this be accomplished with a stand-by generator of 300kW? Thanks for your help.
Can this be accomplished with a stand-by generator of 300kW? Thanks for your help.






RE: Fire Pump Starting
David Castor
www.cvoes.com
RE: Fire Pump Starting
RE: Fire Pump Starting
You may have to feed the controls and the AVR power with a UPS. This starting method is the poor mans VFD and is the easiest on both the motor and the generator. One point to be aware of, should the fire pump be stopped for any reason, the generator will have to be stopped and restarted to restart the fire pump.
But back to your original question:
300 KW should start a 100 HP motor. A PMG option on the AVR will help hold the voltage up.
Why a 15% limit on voltage drop? Who has set this limit?
Will there be other loads on the gen-set?
With regards to David's suggestion of an engine driven pump;
I was involved in discussions concerning back-up power for a fire pump where a diesel engine was suggested. This was in an area exempt from most codes and operating procedures were seldom followed. A strong argument was made to use a back-up generator for both lighting and A/C in the offices and for the fire pump. Human nature and local conditions being what they were, a problem with the backup supply for lights and A/C would probably be fixed fairly soon, whereas a problem with an engine dedicated to a fire pump would probably NOT be fixed until after the next major fire.
There are good reasons to not run a diesel generator at 20% load or less, but if other loads are available so that the fire pump is part of a greater load the total load on the generator is over 50% or the rating, David's suggestion has merit.
Bill
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"Why not the best?"
Jimmy Carter
RE: Fire Pump Starting
RE: Fire Pump Starting
But I won't waste time on voltage drop until I know why you must limit the voltage drop to 15%. The best way to check this is with software from Caterpillar, Onan, F.G. Wilson or other manufacturer. The locked rotor KVA/HP may vary from an extreme low of about 1.6 KVA per HP for a code A motor to over 20 KVA per HP for a code U or V motor.
If you have to know the voltage drop to three significant figures you may want to check the locked rotor code letter.
Bill
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"Why not the best?"
Jimmy Carter
RE: Fire Pump Starting
waross, I'm just trying to help: the start-up voltage drop has to be 15% or less, per the Fire Pump Standard (USA):
NFPA 20, 2010 edition: Article 9.4 "Voltage Drop."
There is an exception for bypass operation with a VFD, but if we're talking across-the-line, the original timm333 post is correct: voltage drop is limited to 15%.
timm333: you might consider a VFD. I was able to easily start a VFD-driven fire pump, 125 HP, using "only" a 235 KW diesel generator. When I was trying to size the generator with manufacturer's software, some of their selections were as high as 500 KW. I finally got together with a sales rep who worked with me to get the KW down, using an over-sized alternator and some other techniques. The job worked just fine. If you're interested, here is contact info for that sales rep:
Contact:
Scott Gagliardi
Alternative Power Systems
412-951-4080 (Pittsburgh, PA)
800-894-4455
Tell him Jeff Miller, P.E. of Upstreet Architects gave the referral.
RE: Fire Pump Starting
Assuming it's a centrifugal and not a gear pump for chemical foam... Different story there.
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
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RE: Fire Pump Starting
Bill
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"Why not the best?"
Jimmy Carter
RE: Fire Pump Starting
RE: Fire Pump Starting
Yes, for several years variable speed drives have been allowed for fire pumps. The VFD job I referred to in my post was built around 2005 - 2006. Get the edition of NFPA 20 Fire Pumps that applies under your Bldg Code. The latest NFPA 20 is the 2010 edition. The VFD requirements for electric motor-driven fire pumps are in 10.10 of the 2010 edition of NFPA 20.
The VFD manufacturer I used was Master Controls; here is a link:
RE: Fire Pump Starting
I want the automatic shedding of HVAC at the time of starting of fire pump. What kind of circuit breaker shall be required for this?
RE: Fire Pump Starting
The load shedding is not done with a breaker. I shed the non-motor loads during start-up with timing relays inside the automatic transfer switch (ATS). Your best bet is to call the sales rep I named in my previous post. He sells the ATS as well as the generator. He can help you work out the starting sequence; he knows all about this stuff. Even if he doesn't cover your territory, he can tell you who your rep is.
By the way, do you realize that an emergency generator is not necessarily required for an electric motor-driven fire pump? If the generator is absolutey required by the scope of work, or your plant standards, OK. But you might want to study 9.3 in the 2010 edition of NFPA 20. An emergency generator is not always required, believe it or not.
RE: Fire Pump Starting
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies