Fire Pump Selection 1

[Ehendrix]

Got a quick question on Fire pump Selection(been a long time since I did this myself), I am sizing a pump for a non high rise NFPA 13 Building, light hazard attic with Attic Sprinklers.
#1 The City water is insufficient to supply the Attic Hip Sprinklers and 48' of elevation & a DCDA Backflow. So I need a small pump probably a vertical Inline 500gpm.

My issue and memory lapse is how to calculate the city water with highest sprinkler elevation to give me my pump head pressure so I can therefore size a pump for this project.

Any help to kind of bump me in the right direction? Thanks!

 

[TravisMack]

Height of sprinkler * 0.434 = elevation pressure
Starting pressure of sprinkler from listing
Estimated friction losses (20-30 psi)
Safety margin required
BFP losses
Losses through valves in riser

Add all of those up, and that is a rough estimate of your pressure demand. Subtract the pressure available from the city at system flow and you get how short you are. Choose a pump that will meet those requirements.

Remember that pump churn + static can not exceed pressure listing of system components. This is typically 175 psi.

This is just for estimate purposes. You should of course have actual numbers from your calculations that will nail down the friction losses and such so you can get your pump requirements.

If you are using Tyco Attic sprinklers, you may be able to get by with less than 500 gpm pump. The cost difference is pretty significant with a 300 gpm and 500 gpm pump when you figure in all of the stuff in the pump room.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[Ehendrix]

Thats about where I was at, thanks for your time sir!