ESFRs Allowed on Single Interlock Preaction?

4/24/2026

Would ESFR K25.2 be permitted to be installed on a single interlock pre-action system?

I have a system conversion that is currently a gridded warehouse with K25.2 ESFR pendents that the client wants to convert to single interlock. The system will be converted to not be gridded anymore, but I am not seeing any clear information on whether the existing ESFR can remain.

If we were to remove the sprinklers, it would now dive into possible in-racks to protect the class IV storage. Warehouse is 35ft max height, bar joist.

Thanks in advance.

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9 Comments

Pete H

4/24/2026 06:14:02 am

Depends if the listing states that it's for wet systems only. Some will list that, they'd be right out. Some don't mention it.

The Viking VK510 ESFR, when used with the Viking Preaction valve has a write up about using it for cold storage in a preaction system, so while it's doesn't say "Wet/Preaction" or "Wet only", we can read about it being tested with UL for a preaction system.

https://www.vikinggroupinc.com/sites/default/files/databook/freezerstorage/120805.pdf

Brett

4/24/2026 07:50:36 am

That pdf is from 2005 so I wouldn't recommend referencing it without contacting Viking. The listing for the VK510 says wet systems only.

Anthony

4/24/2026 08:48:31 am

they tyco/JCI Quell / VanQuish system is used in freezer applications if you're asking about a dry type system.

NFPA13-22 14.2.2

ESFR sprinklers shall be used only in wet pipe systems unless specifically listed for use in dry systems or preaction systems.

Jonathan Griffin

4/24/2026 09:22:29 am

If using NFPA 13 (2019 or better), Pendent & Sidewall sprinklers can be used (w/return bends) where in an area maintained above 40'f. This may address the orientation issue... ESFR sprinklers are listed for Wet-only as far as I can determine (there may be one out there, I just don't see it). Using ESFR sprinklers that are also listed for non-storage use may be a way to go (K14 & K16.8 are available in this activation (CDMA - ELO) mode.
If the client wants to go to Pre-action then there may be some extra work involved... In-rack becomes a possibility for sure! Good luck

Glenn Berger

4/24/2026 09:31:49 am

Check the listing of the proposed mfg. and make sure the applicable ones get installed.

danefre

4/24/2026 01:23:55 pm

ESFR is out of the question, no listed product available.
CMSA doesn't give you Dry options per Table 22.4 for Class IV.
CMDA will require in-rack at your storage/building heights and Class IV
Chapter 24 has no alternative designs for Class IV dry.

Short answer is put a ceiling over the "sensitive" area that requires pre-action. And/or separate it with full height walls. Leave the wet ESFR at the roof alone, it was put there for future flexibility.

John D

4/24/2026 03:53:18 pm

Wouldn't it be possible for Table 24.3.1 to be utilized since in some cases you can consider a single interlock to be a wet system?
An ESFR would be redundant in pre-action but what about a extend coverage k25.2 upright?

danefre

4/27/2026 10:08:08 am

Single interlock can't be considered a wet system. The only connection is that you are not required to increase your remote area for SI when using the Density/Area method.

EC25 design is not applicable per chapter 24. All options for Class IV are for wet systems only.

I can't even imagine how they would test these with so many variables around electronic detection, tens of different preaction systems and strict activation time to not overtax the system.

4/24/2026 06:27:40 pm

There's not enough information here regarding commodity classification and proposed storage height, but here's an idea.

Change the ESFR to CMDA (high temp), leave the near main, run a new connecting feedmain from the near main to the far main, replace the far main with the same size pipe as the near main (if necessary for calcs, install a new center fed main, disconnect the branchlines to have 3 trees (1 using of the existing near main, 1 using the existing far main now replaced with larger pipe, and 1 with the center fed main). Figure out how high of a density you can achieve without exceeding 750gal (or highest capacity with working fluid delivery calcs). Lower the storage height based on density achievable for ceiling only (depends on your water supply) and/or add in-rack sprinklers (also preaction) with protecto wire.

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ESFRs Allowed on Single Interlock Preaction?

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