Waterflow Req'd for HVAC Shutdown in 90A?

3/30/2023

An engineering firm has insisted that a waterflow activation shutdown the HVAC system and cited NFPA 90A: A.6.4.3.

A.6.4.3 Where automatic water sprinklers are provided and zoned to coordinate with the HVAC zones, their water flow switches should initiate devices for the functions described in Chapter 6.

Each floor of the building has one HVAC zone and one sprinkler zone (floor control valves).

The HVAC system has the appropriate duct detectors and functions.

The only instance I have experienced using flow switches for HVAC control is when there is no automatic smoke detection and the flow switch is used to start the smoke control system for that zone.

What are your thoughts?

Is a waterflow switch required to shutdown an HVAC system on this premise?

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9 Comments

Dan Wilder

3/30/2023 07:48:41 am

I've only ever used this approach in Casinos, large open areas to start an exhaust cycle within the zone of water flow and the adjacent zones went into supply venting (no AC or Heat) to slow the spread of smoke across large open areas. More recently Data centers to control the CRAC/CRAH units within individual data halls along with the shutdowns of the large HVAC units to prevent over pressurization of the hall or blowing out the dampers.

I would think the main trunk fire/smoke dampers that supply any floor would automatically close and any HVAC units on the floor would only be recirculating the air from that floor (this is separate from the pressurized stairs or any refuge floor considerations). In that case, any unit with a damper would just close upon smoke detection anyway so the end result is the same.

It's a BMS controls side issue and doesn't affect anything on our fire/life safety side....was there a concern you had that impacts the fire sprinkler systems that I am missing?

Jesse

3/30/2023 08:07:32 am

I'm curious as well. Is there a requirement from the engineering firm that impacts fire-protection other than the provision of a flow switch?

Glenn Berger

3/30/2023 08:13:48 am

This is a new one for me. You can use the intro paragraph to the Appendix - that the Annex A is not of the NFPA document ...

Todd E Wyatt

3/30/2023 08:16:01 am

When a Code (IBC) or standard (NFPA 90A) uses “SHOULD”, it “indicates a recommendation or that which is advised but not required.”

When a Code (IBC) or standard (NFPA 90A) uses “SHALL”, it “indicates a mandatory requirement.”

This engineering firm can “request” that A.6.4.3 be met but they cannot “insist” this “recommendation” be met.

REFERENCES
2021 NFPA 90A Standard for the Installation of Air-Conditioning and Ventilating Systems

Chapter 2 Definitions
3.1 General.
The definitions contained in this chapter shall apply to the terms used in this standard. Where terms are not defined in this chapter or within another chapter, they shall be defined using their ordinarily accepted meanings within the context in which they are used. Merriam-Webster’s Collegiate Dictionary, 11th edition, shall be the source for the ordinarily accepted meaning.
3.2 NFPA Official Definitions.
3.2.4 Shall.
Indicates a mandatory requirement.
3.2.5 Should.
Indicates a recommendation or that which is advised but not required.

Chapter 6 Controls
6.1 Wiring.
The installation of electrical wiring and equipment associated with the operation and control of air-conditioning and ventilating systems SHALL be in accordance with NFPA 70.

6.4* Smoke Detection for Automatic Control.
A.6.4
The use of smoke detectors in relationship to HVAC systems and high air movement areas and the details regarding their optimum installation are covered in NFPA 72.
Protection provided by the installation of smoke detectors and related requirements is intended to prevent the distribution of smoke through the supply air duct system and, preferably, to exhaust a significant quantity of smoke to the outside. Neither function, however, guarantees either the early detection of fire or the detection of smoke concentrations prior to dangerous smoke conditions where smoke movement is other than through the supply air system.
Where smoke-control protection for a facility is determined to be needed, see NFPA 92.
6.4.3* Function.
6.4.3.1
Smoke detectors provided as required by 6.4.2 SHALL automatically de-energize their respective fans upon detecting the presence of smoke.
6.4.3.2
Where the return air fan is functioning as part of an engineered smoke-control system and a different mode is required, the smoke detectors SHALL not be required to automatically stop their respective fans.

A.6.4.3
Where automatic water sprinklers are provided and zoned to coordinate with the HVAC zones, their water flow switches SHOULD initiate devices for the functions described in Chapter 6.
Sprinklers are often tested weekly. Where it is desirable to prevent the accompanying automatic shutdown of the fan system(s) referred to in 6.4.3, a means can be permitted to be used to avoid such shutdown temporarily, provided one of the following occurs:
(1) A trouble signal is sustained in the sprinkler supervisory system until the automatic shutdown provision is restored.
(2) The automatic shutdown provision is restored at the end of the time period necessary to test the sprinkler system, its alarms, and related elements.

Todd E Wyatt

3/30/2023 08:35:00 am

“A.6.4.3” is part of “Annex A — Explanatory Material” :

“Annex A is NOT a part of the requirements of this NFPA document but is included for informational purposes only. This annex contains explanatory material, numbered to correspond with the applicable text paragraphs.”

Accordingly, information in Annex A is not enforceable ... regardless IF it uses "SHOULD".

Todd E Wyatt

3/30/2023 09:47:07 am

... regardless IF it uses "SHALL" ... which it does not.

Brad K

3/30/2023 10:49:11 am

This looks to be a case of the "SHOULD" costs an extra and the "ANNEX A" costs an extra (unless Annex is adopted in amendments by AHJ).

Chad

3/30/2023 02:41:00 pm

That's a big ol RFI that should sound like:

Why? and who is paying for this annex material you reference?

James Pazuchanics

7/25/2025 10:29:51 am

This requirement would come from the IMC or the Local amendments to the IMC for fan and damper control. New York City has this requirement in the NYCMC along with any automatic fire detection device within the HVAC zone. The issue is that most HVAC zones are not coordinated with sprinkler zones and this can become very complicated. Which leads to a over-simplified approach of any automatic fire alarm shutting down all fans and dampers. Have seen local amendments that require a switch at the FACP panel to do just that.

Waterflow Req'd for HVAC Shutdown in 90A?

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