I'm new to this industry and I've been really trying to pick apart NFPA 13.
I have a question related to determining the area of sprinkler operation of a dry pipe system with high temperature sprinklers. The system is providing coverage of an outdoor chemical storage canopy.
Dry System due to freeze potential
Extra Hazard Group 1 (0.30 gpm/sf over 2500 sf) per NFPA 13 Fig. 184.108.40.206.1
High temperature rated sprinklers per NFPA 13, Section 220.127.116.11.4
My question is regarding adjustments to the area of sprinkler operation. Dry systems are to be increased 30 percent per 18.104.22.168.5, then it states in 22.214.171.124.6 that the area can be reduced by 25 percent when using High temperature sprinklers. Multiple adjustments can be compounded.
Increase: 2500*30% = 750 sf
Decrease: 2500*25% = 625 sf
2500 + 750 - 625 = 2625 sf
A conservative approach would be to ignore the 25% reduction, but I'm curious what is actually required per code.
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7/10/2019 07:52:21 am
To compound multiple adjustments to a design area the math would look like this (assuming you do not have to apply a 30% increase for sloped ceilings, section 126.96.36.199.4):
7/10/2019 07:55:00 am
While the conservative approach always sounds nice and comforting to us as engineers/designers, the reality is that extra coverage area is unnecessary per the code. The exceptions exist for a reason, and your salesperson will probably not be thrilled with the extra cost that is incurred by your safety margin.
7/10/2019 08:01:26 am
I stand corrected. Your (and my) design area adjustment is wrong and should follow what Wayne references and explains above. Can't overlook the annex material...
7/10/2019 02:56:57 pm
It is very important, you have an Ocupancy not an Storage Application.
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