Waterflow for Each Floor in 47,000 sqft Building?

9/27/2023

We have a small building (less than 47,000 sqft) with basement, ground floor, first floor and roof protected with a sprinkler system. Fire pump room is in the basement.

In NFPA 13-2022, Section 16.9.10.3, there is no need to install floor control valve assembly (no need for sprinkler system either, but client insisted).

I've never designed such a small system; and as a result I have a couple questions:

(1) Is one flow switch after the fire pump sufficient for all floors? If not, do I need to provide each floor with a flow switch?

(2) Is an alarm check valve assembly required? If so, can it be used instead of a waterflow switch, or do we need to install both?

Any other tips for a smaller building would be greatly appreciated. Thanks in advance.

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6 Comments

Pete H

9/27/2023 06:44:36 am

One Flow switch and one alarm valve is sufficient provided you don't have further floor control valve assemblies separating them. As you stated there is no need to install a floor control valve assembly, but client insisted.

Since the client is insisting on floor control valve assemblies, you would not (in my opinion) be providing floor control valve assemblies without flow switches as flow switches are part of floor control valve assemblies. Since you are providing different control and checks at the floor control valve assemblies, they all need flow switches to be floor control valve assemblies.

Similarly, you could only use one alarm check valve, and you can technically void it calling each of your floor control valve assemblies separate risers on your system (as each floor control valve assembly contains a riser check valve), however this means your system cannot feed any sprinklers before hitting these respective floor control valve assemblies (including a sprinkler over the pump room), and I'll be honest.... wiring your fire alarm now sounds like a nightmare.

Also, it's weird you require a fire pump on a building that is so small it doesn't require sprinklers. Is this a commercial building in a residential neighborhood?

Anyway, as always, take with a grain of salt, it's early in the morning and I didn't open any books to double check myself on this one.

9/27/2023 08:17:33 am

1) As per NFPA 13, yes, however local building codes may differ.

2) An alarm check valve assembly (I assume something similar to the AV-1-300 Alarm Check Valve) has the ability to have a pressure flow switch installed on the typical trim package. Installing a vain type flow switch down stream of the alarm valve would be redundant.

Glenn Berger

9/27/2023 08:20:58 am

1) Is a flow switch required for each floor? Is the 47,000 square foot the total floor area in the building or is that 47,000 square feet per floor? What is this building occupancy?

The answers to the above questions will assist in giving a proper response.

2) If you provide an alarm check valve with an alarm pressure switch (with retarding chamber) than you are providing a means that indicates that there is sprinkler flow downstream of the alarm check valve and therefore a vane-type flow switch would not be required.

Jesse

9/27/2023 08:25:47 am

One flow switch should be sufficient provided your local AHJ doesn't have amendments that require them for each floor.

Inspector

9/27/2023 09:02:44 am

You must live in a big city if you think 47,000 sq ft is a tiny building LOL. You mention ground floor and first floor...Is this a 2 story building?

Connor R

9/27/2023 01:55:01 pm

I'm reading this as a building with a basement, 2 stories above grade, and a roof level which are all sprinklered. Is there a rooftop bar or something, or a mechanical penthouse? Do you really mean "roof," or do you mean "attic?"

Per NFPA-13-2019 16.9.11, floor control assemblies are required for buildings exceeding two stories in height. Depending on your local amendments, an occupied roof or accessible attic may count as a story.

If not, you will still need a flanged joint or mechanical coupling at the riser at each floor. This allows the main to be capped at that location so that the floor can be individually worked on for repairs or future alterations. See NFPA-13-2019 Figure A.16.9.11.5 for a basic detail on this configuration.

To answer your question, a single flow switch at the main riser is generally permitted as long as the total area of everywhere that is covered by the single sprinkler system riser does not exceed the coverage area limitation for that occupancy hazard (52,000 sq ft for Light or Ordinary Hazard, 40,000 sq ft for Extra Hazard per NFPA-13-2019 Section 4.5).

If you have an attic or roof dry system, that will either be its own system, or a subset of the larger system that it feeds off of depending on the configuration. If a subsystem, that area counts towards the totals above. The dry riser will need to be monitored for supervisory air and waterflow regardless.

P.S. For maintenance and installation reasons, an alarm check valves are less common than a riser manifold with a control valve, check valve, and flow switch. These require less trim and come pre-assembled for most sizes.

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Waterflow for Each Floor in 47,000 sqft Building?

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