When calculating a sprinkler system using the area/density method, I have heard several schools of thought:
I tend to go with the most demanding as I don't worry about bidding projects most of the time, but in short, I was wondering what the consensus was concerning validity of each of these methods.
Thanks in advance.
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2/21/2022 07:52:47 am
1 & 2 would be the "most" correct and interchangeable, with #3 be applicable in some specific circumstances but still allowable.
2/21/2022 08:00:47 am
Assuming you're doing a demand calculation, the purpose of the calc is to determine the minimum water supply required to ensure all sprinklers are providing the water density for the hazard classification given the system layout.
2/21/2022 08:10:21 am
Item 1 is standard practice.
2/21/2022 08:24:49 am
What say NFPA about that ?
2/21/2022 08:25:19 am
With in the D/A method there is a clear method to determining coverage area per sprinkler ie:S x L as defined in section 8.5 (NFPA 13 2016).
2/21/2022 08:26:10 am
Item 1 would be standard.
2/21/2022 08:37:35 am
I always use #2.
2/21/2022 10:44:51 am
2/21/2022 01:34:41 pm
2022 edition of NFPA 13
2/21/2022 10:59:37 am
I will explain you how I review hydraulic calculation as a loss prevention engineer working for an Insurance Company.
Carlos E. Jara Fire Protection P.E. (Ca. license #1056)
2/23/2022 11:29:10 am
Franck, the required minimum pressure is 7.1psi, not 8.1
2/21/2022 02:40:18 pm
I have always used the square footage the sprinkler is covering. Like mentioned above, software will determine the most remote sprinkler and work backwards. Therefore, a sprinkler in a closet might require far less pressure than it will receive. If you use software like Revit (HydroCalc), you can input Sq.Ft. per head. Old old software like Hass, you are stuck with a single Sq.Ft.
2/21/2022 02:42:18 pm
Method #1 is correct when using extended coverage, residential, or other heads with specific areas and pressures. Also acceptable for CMDA standard spray heads but kind of a lazy way to do it.
2/22/2022 09:41:15 am
I always use method 2. This comes in handy in trying to see what heads are driving up the flow and thus the pressure.
2/22/2022 10:42:55 am
I usually use Option #2, but I will use #3 if each sprinkler area is similar. For example, if there were three sprinklers covering 94, 98, and 100 sq.ft respectively; I might calculate them each at 100 and call it a day.
2/23/2022 07:14:03 am
Would agree with the consensus that 1 works for extended coverage, 2 works for standard coverage.
2/23/2022 01:35:04 pm
Might I ask the question from a fire district plan review perspective? If I am reviewing a fire sprinkler plan and let say these are the design parameters used:
2/23/2022 02:40:23 pm
Great question Brad. If during initial review you discovered a head in the calc area spaced at 225 sqft lets say, when the designer had 200 sqft max in the calc, then yes. I would ask them to revise their calc. If you happened to find some heads outside of the calc area spaced more than 200 sqft, then personally no I would not ask for more calculations to be done, or the original revised.
2/24/2022 07:17:05 am
Casey, thanks for your response and explanation. It is always good to get feedback from others within the same field!
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