supply mode calculations for NFPA13

[6877263]

Hello all,

I'm reviewing plans for a sprinkler system that is designed for OH-2.

The water supply for the sprinkler system is a diesel engine pump (1500 GPM @ 100 PSI), that is supplied from a water tank with the capacity of a 20,000 gallons.

The hydraulic calculations were executed in the "Demand mode", and they require 300 GPM @ 50 PSI, for a duration of 1 hour, which means a total demand of 18,000 gallons.

On the paper everything looks fine, but I'm a bit concerned and would like to hear your opinions on this issue.

I'm affraid that the pump is to large for this project, and the actual amount of water that will come out of all of the sprinklers in the MDA will result in the usage of the water tank in less than 1 hour, thereby violating the necessary duration.

I asked the designer to submit calculations for the system using the "Supply mode", but he said that there is no reference to my request in the NFPA 13.

What is your opinion on this matter?


Thanks,
Issac

 

[TravisMack]

He's correct. There is no reference to that in NFPA 13. It is easy to do with all software packages on the market.

I can't think where water tanks are based on supply calcs for sprinklers.

NFPA 13 (2016 ED) 11.2.3.2.1.1 The water supply requirement for sprinklers only shall be calculated from the
density/area curves of Figure 11.2.3.1.1 or from Chapter 22 where density/area criteria are
specified for special occupancy hazards.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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