6-Sprinkler EC Calculation Apply to All Systems?

6/22/2022

I was milling around in NFPA 13 and I saw the “alternative” design approach chapter (Chapter 21) that it mentions that in the case of Extended Coverage sprinklers that the 6 flowing sprinklers must meet a minimum coverage area of 768 sq ft.

I haven’t run into a scenario where this would be an issue… but is that generally applicable to all systems or is there some sort of “alternative” design trigger where this is necessary?

I was just always under the impression that I only needed to calculate 6 Extended Coverage K25.2 sprinklers and that was it.

This is Section 21.1.8 in the 2016 Edition of NFPA 13. I appreciate the clarification.

4 Comments

Alex

6/22/2022 07:03:58 am

Hi,

I have never used Chapter 21 personally. I'm confused on how you would ever have a design area less than 768 ft2 with (6) sprinklers flowing 14x14 (1,176 ft2).

I'm looking forward to seeing what others have to say here and learn something new today!

Alex

Dan Wilder

6/22/2022 08:17:54 am

This section 21.1.8.1(3) is a subsection specific to a storage area design (21.1.1 "Sprinklers intended to protect storage fire risks....criteria that are different from the design criteria specified for the sprinklers described in Chapters 12 through 20..." and are based on results from full scale fire tests as described in the annex with a required safety factor.

This isn't for use in a light or ordinary hazard (non-storage) hazards.

.

Anonymoose

6/23/2022 03:31:39 pm

I think it's referring to listings by the sprinkler manufacturers, who will sometimes go and see if they can't fill specific niches by proving their product with full scale fire tests. So they're setting minimums for these specialized design criteria. I don't do a lot of storage so I can't speak to specifics, but, for example, I think I've seen some EC K25 heads that have listings for specific storage commodities and configurations.

Casey Milhorn

6/24/2022 12:04:47 pm

I believe a few years ago we did have this situation where we wanted to use EC25s at the roof and under some mezzanines. The mezzanines (from memory) had solid steel beams with pockets at 10'x12'. To keep consistency and to save 1 head per pocket, we went that route, but had to calculate 7 EC-25 heads in lieu of 6.

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6-Sprinkler EC Calculation Apply to All Systems?

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