Allowed to Calculate ESFR at a CMDA Design?

12/21/2023

I have a K14 ESFR system in a tall building; 45-ft peak and 35-ft eaves, that was hit by the changes in NFPA 13 and there is now a recommendation to upgrade protection to K25 ESFR sprinklers due to the roof height.

The current design is a very strong 12 K14 @ 90 psi and the storage is low at 16-ft of palletized Class III and IV goods.

Based on the current storage arrangement, 2022 NFPA 13 allows for either K25 ESFR system or a CDMA design of .64/2,000 using ordinary temperature sprinklers.

Is is permissible to recalculate ESFR systems with a CDMA design?

If so, is there any specific mention or directive in code?

I am not a designer but back of napkin math indicates I have a 1.33 gpm/sqft. density over the first 1,200 sqft based on the ESFR design and probably a .80/2,000.

Thanks in advance.

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10 Comments

Anthony

12/21/2023 07:07:31 am

No its not acceptable to use ESFR in CMDA design. The problem is the different listing of the head. You can only use ESFR sprinklers in ESFR design.

I recently ran into a similar issue looking at roll paper design with K16.8 heads and the differences between CMDA, CMSA and ESFR and FM 8-21 vs NFPA13 ch19. Note also CMDA and ESFR sprinkler instillations have very different obstruction rules too. All that goes into the design considerations.

Lastly, K14 heads are 3/4'' outlets and K25 heads are 1'' outlets so you're going to need to drill a ton of new mech tees in or re-pipe the branch lines so I'm not seeing the benefit there.

Patrick

12/22/2023 10:40:20 am

Let me simplify the point of the question:

If I replace the K14 ESFR heads with K11 Storage heads and then calculate a CDMA design that is acceptable per NFPA 13 (.64/2000), I now have a system that is compliant/approved for class 4 storage.

Is my fire protection any better for having made this change or in fact am i spending a lot of money to decrease the actual effectiveness of my system.

Clarifications:
1. This is for insurance and determination if a sprinkler system will provide adequate protection. Will it put the fire out.

2. All density estimates considered current total system flow and flow per head based on the existing design (12 @ 90 or 134 gpm per head 1600 gpm for the system). I then extrapolated the design area out and the corresponding decrease in density. You will be pushing the same amount or less water over a larger design area so friction would not go up.

3. This is not orthodox, but goal is to prove existing system is acceptable as is.

Franck

12/21/2023 08:09:29 am

Answer is simple : no !
ESFR are not on control mode but extinction mode.
Design is very specific and minimum pressure is a « no deviation » requirement

Glenn Berger

12/21/2023 08:10:31 am

Anthony statement is spot on. Do not mix specific calculation methods that are applicable to specific specialize sprinklers.

Jes

12/21/2023 08:34:27 am

The short answer is "NO".

This is primarily due to the listing of the sprinkler. This sprinkler is a Suppression Mode sprinkler, not a Control Mode sprinkler.

However, I used to do loss control engineering for a property carrier that saw things differently. If we calculated a system at 0.64/2000 we could determine it "adequate for underwriting".

Dwight Havens

12/21/2023 09:22:37 am

"I have a K14 ESFR system in a tall building; 45-ft peak and 35-ft eaves, that was hit by the changes in NFPA 13 and there is now a recommendation to upgrade protection to K25 ESFR sprinklers due to the roof height.

Tell me more...

Has the existing protection been shown to be inadequate? Have the changes in NFPA 13 been adopted retroactively? Is this due to the slope of the ceiling (roof)? Who is the AHJ that is making the recommendation to change the protection?

Franck

12/21/2023 11:57:08 am

“but back of napkin math indicates I have a 1.33 gpm/sqft. density over the first 1,200 sqft based on the ESFR design and probably a .80/2,000”

This is unfortunately not correct.
You can’t make a simple calculation rule like that…
This does not take into consideration additional friction losses due to extended pipe length and corresponding extra flow requirements that does not follow a “straight” law, but logarithmic and exponential…
A .3/2000 is not equivalent to a .6/1000.

Not to speak about the minimum pressure required to properly operate ESFR, whatever the occupancy below. Remember that if you have a too high clearance, you have to consider as if the storage was higher.
And if the pressure is too low at the ESFR sprinkler, the water distribution pattern and droplet size and distribution are not correct.

Jay

12/22/2023 01:38:51 pm

Install a ceiling at the 35ft eave height and the sprinkler system won't need to be modified.

Jay

12/22/2023 01:43:51 pm

Clarification....obviously modifications will be needed to protect below the new ceiling, but the ESFR design of K14 heads can remain.

sean

12/31/2023 06:25:52 pm

I am not sure why we are mixing the versions of the standard?
Is new work triggering this? That would only affect the scope of work.

If the storage isn't changing I would not be applying a new standard.

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Allowed to Calculate ESFR at a CMDA Design?

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