When to Apply Minimum Area for High-Temp?

12/24/2019

If I have multiple compounding remote area adjustments, when does the minimum remote area size for high-temperature sprinklers get applied?

For example, if there is a dry system protecting storage starting at 2,500 sqft, which calculation is correct?:

(a) 2,500 sqft x 0.75 (high-temperature reduction) = 1,875 ... rounded up to 2,000 sqft for minimum area, then 2,000 x 1.3 (dry system area increase) = 2,600 sqft.

or

(b) 2,500 sqft x 0.75 (high-temperature reduction) = 1,875 ... 1,875 x 1.3 (dry system area increase) = 2,437 sqft, which is greater than the 2,000 sqft high-temperature minimum.

Thanks in advance!

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3 Comments

Wayne Ammons

12/24/2019 09:45:56 am

Referencing NFPA 13, 2013 Edition

Mathematically, it doesn't matter in which order you make the adjustments to the remote area in accordance with sections 11.2.3.2.3 (Quick-Response Sprinklers), 11.2.3.2.4 (Sloped Ceilings), 11.2.3.2.5 (Dry Pipe and D.I. Preaction Systems), or 11.2.3.2.6 (High Temperature Sprinklers). I think there is a misinterpretation of the minimum 2,000 sq.ft. requirements of section 11.2.3.2.6. In my opinion, the math shown in example "b" would be correct. The math shown in example "a" is more conservative, but I do not think that is the intent of the standard.

Interested in if someone else has a more definitive answer.

Juan M

12/24/2019 10:50:39 am

This is a good question. After going over NFPA 13 section 11.2.3.2.7, A.11.2.3.2.7, & 11.2.3.2.7.1 (2016 edition), I think "b" is correct. If you do the math as follows, accounting for the dry system increase first, then take the high temperature reduction you get "b".

2,500 SF x 1.3 (dry system area increase) = 3,250 SF
3,250 SF x 0.75 (high temperature reduction) = 2,437.5 SF

Jonathan Joseph

12/24/2019 11:14:35 am

I believe the intent of the 25% high temperature reduction for Extra Hazard occupancies is to give additional 5% reduction to dry systems but keeping a wet system above 2000sqft as a standard for Extra Hazard.

You want to use (b)

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