I have a mixed use Retail/Residential building protected per NFPA 13. I am calcing the retail area at 0.20 gpm. The space is not large enough to get the full 1500 sq ft so I have a few heads in the adjacent corridor in the calcs to make up the difference. Normally, I calc the OH heads at 0.20 gpm/sq ft and the LH heads at 0.10 gpm/sq ft. However, the engineer has asked me to calc the LH heads at the 0.20 gpm rate since the wall separating the two areas is not a rated wall. The problem I have with this is that the LH heads are spaced for LH occupancy so they will become the most demanding sprinklers (14 ft x 12 ft spacing = 168 sq ft x 0.20 gpm = 33.6 gpm as opposed to the OH heads at 125 sq ft x 0.20 gpm = 25 fpm). This doesn't seem right, but I cannot find a foothold in the standard to begin the "discussion". 2013 edition is the adopted standard and it reads "Each sprinkler in the design area and the remainder of the hydraulically designed system shall discharge at a flow rate at least equal to the stipulated minimum water application rate (density) multiplied by the area of sprinkler operation (23.4.4.6.1)" This seems to support his request. Any help out there?
Thank you, Micah Davis www.dynamicfiredesigns.com
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