Wet-Pipe Sprinkler to Circulate Heat/Cool Water?

11/30/2021

Is a wet-pipe sprinkler system allowed to be used to circulate water for heating and cooling purposes?

I am designing a wet-pipe sprinkler system under NFPA 13-2019 Edition.

The building owner would like to use the sprinkler system as part of the building's heating system. I can find this described as "allowed" in NFPA 13-2016, but not in the 2019 Edition.

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12 Comments

Pete H

11/30/2021 07:00:57 am

I'm not sure where this is allowed in 2016 edition. I know 2013 edition talks about that situation as a "Circulating Closed-Loop System" in section 7.7 "Automatic Sprinkler Systems with Non-Fire Protection Connections", but that was removed in 2016 (more here: https://www.csemag.com/articles/combining-hvac-fire-suppression-piping/ ).

Can someone show where it's allowed in 2016? It might be easier to figure out where the verbage got moved to in the 2019 revision from that base point.

Nick Pierce

4/27/2022 11:24:57 am

Can anyone provide a sequence of operations for a closed loop system? More specifically the order of events when a head is opened. Trying to test a system and a water flow alarm is not reporting back to the fire panel.

Moderator

4/27/2022 11:50:44 am

Hi Nick, to get traction you might consider posting this as a new question here:
https://promote.meyerfire.com/ask

Thanks!

Jared

11/30/2021 08:14:27 am

From the NFPA 13 2019 Handbook. Chapter 8 - "Prior to the 2016 edition, NFPA 13 provided guidance on circulating closed-loop systems. The technical committee on sprinkler system installation decided to remove the language related to circulating closed-loop systems because they were concerned that additional fluids used to extend the life of nonsprinkler system components, such as heating units, chillers, or companion equipment associated with heating, ventilating, and air conditioning (HVAC) systems, might create a compatibility issue with some sprinkler system components. "

Glenn Berger

11/30/2021 08:15:51 am

In the 2016 version - See 25.3.

This information was move to Chapter 28 in the 2019 version. However I do not see evidence of any allowance for a circulating closed loop systems.

Franck

11/30/2021 11:23:09 am

At the end of NFPA 13 Edition 2019, there is a table with correspondences of section numbers between 2016 edition and 2019 edition.
There is no correspondence for section 25.3, which means that the use of circuakting closed loop systems have been abandonned.
In the 2019 Edition, there are 2 references for closed loop systems, one is in chapter 30 (Marine Systems) to indicate that "Circulating closed loop systems shall not be permitted", and one is in teh Annex section of 27.1.5 where there are 2 Working Plans for Circulating Closed-Loop Systems. But probably a mistake to remove the drawings as they have not been reproduced in the 2022 Edition.

In the 2022 Edition, the only reference for closed loop systems is in chapter 31.3.4 (Marine Systems) to indicate that "Circulating closed loop systems shall not be permitted".

Jesse

11/30/2021 08:22:25 am

I'm not a fan. We have several of these tri-water systems our service division attends to. They were pretty popular a few years ago. The concept is defined in 2016 NFPA 13 3.4.2 just as a general concept. Its not disallowed per se. Thankfully in my area they have fallen out of favor

Franck

11/30/2021 11:30:47 am

In addition to all above comments, I see many possible issues with such systems.
First one is to be sure that all materials used on the heating systems are pressure compliant with the sprinkler system (175 psi ?)
Second, as you will circulate water, eventhough this is a closed circuit, with no introduction of "new water", you may accelerate corrosion issues and spread other problems such as MIC.
Third, any time you need to make maintenance on the heating system, and it should be more frequent that for sprinkler systems, you may need to empty the water in a portion of the system and bring new water + air afterwards = more corrosion potential.

And now, my personal opiinion: a sprinkler system should be used for firefighting purposes only. If you add anything else, you will reduce the overall reliability of the system. And the cost saving at the initial stage can result in a huge amount of money spent afterwards.

Jack G

11/30/2021 11:49:44 am

Having installed these systems in the 90 s , there are many characteristics you have to follow, to make these things work properly .
1. Pressure rating of fixtures.
2. Sprinkler head temperature- must increase to intermediate temps.
3. Velocity: unlike sprinkler systems, velocity ( creates noise) in this type system— all the time it’s circulating if pipe size is too small—usually you can’t exceed 6-7 FPS in your piping. So your sprinkler system is way oversized.
4. Must check off flow switch to prevent movement.
I did my best to talk engineers out of this, but I did do a dozen or so of these.

Dan Wilder

11/30/2021 01:20:58 pm

I've only done TI's on these but some issues we ran into in addition to the above comments on design considerations:

Return Bends - the circulating system ended up putting deposits in the existing drops when piped from the side or bottom (as I have never designed one, my assumption is it should be a requirement).

HVAC shutdowns for chemical adding or flushing - this often times ended up taking out the entire system and we had issues with notifications back to the FD & building owner as to impairment with the ITM of the HVAC system.

Draining was a nightmare with the all the loops (HVAC tended to go up over then down vs under and back up) to avoid a low spots for sediment to build up.

Alex

12/1/2021 10:31:23 am

Hi,

For new construction, I would recommend you stay away. The cost savings would be negligible in the long run and you will have a ton of headaches on system maintenance.

Alex

sean

12/31/2021 06:37:39 pm

i would recommend against this as the design now has to meet plumbing and fire sprinkler rules

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Wet-Pipe Sprinkler to Circulate Heat/Cool Water?

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