Use QR Reduction for Miscellaneous Storage?

7/25/2023

We have a wet system. Inside the system is a walk-in freezer, which has less than 10-ft of rack storage, Class I-III commodities, protected by dry pendent sprinklers from the wet system. Ceiling height is 11'-9".

Using the chart for Miscellaneous Storage up to 12-ft in Height (Table 13.2.1 of NFPA 13, 2016 Edition), thi is to use the design curve for OH2 on Figure 13.2.1.

Since the ceiling height is so low, and it's equivalent to an OH2 design curve, there's a request to apply Figure 11.2.3.2.3.1 and reduce the design area within that freezer by 37% and use the smaller hydraulic design area.

However, it's not an Ordinary Hazard area, it's a Miscellaneous storage area that is equivalent to an OH2 curve.

Are you permitted to use the remote area reduction for Miscellaneous Storage here?

Thank you for your time.

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9 Comments

Pete H

7/25/2023 06:43:46 am

So I think I may have asked this one... and it's one I'm pretty sure I've answered in the mean time:

NFPA 13 (2016) 13.2.2: Installation criteria as permitted by NFPA 13 and design criteria and modifiers as permitted by the density/area method of Chapter 11 for ordinary hazard Group 1, ordinary hazard group 2, and extra hazard group 1 and extra hazard group 2 occupancies shall be applicable.

Yeah, you can do it.

Anthony

7/25/2023 08:09:23 am

The system is wet but the drops will have to be dry for the freezer. Does anyone think that would affect the "wet system only" stipulation on 11.2.3.2.3.1?

Anthony

7/25/2023 08:10:42 am

I'd also note that high temp heads should be used in all freezers so heads don't go off during a defrost cycle.

Taylor

7/25/2023 08:17:50 am

No, that doesn't change that it is a wet system. Dry sprinklers do not have the same delayed discharge inherent with a dry system.

Casey Milhorn

7/25/2023 08:17:07 am

I was about to say no until I saw Pete's reply. If you were to read the reduced area section for QR sprinklers (see below) you would have to say no at first. But I'm with Pete on this one, it appears you can. Make sure you are using QR dry pendent sprinklers. Sometimes those can get hard to find in the larger orifice sizes, so make sure the model used does indeed have the QR listing and it's applicable to the spacing and intended use.

11.2.3.2.3 Quick-Response Sprinklers.
11.2.3.2.3.1 Where listed quick-response sprinklers, including
extended coverage quick-response sprinklers, are used
throughout a system or portion of a system having the same
hydraulic design basis, the system area of operation shall be
permitted to be reduced without revising the density as indicated
in Figure 11.2.3.2.3.1 when all of the following conditions
are satisfied:
(1) Wet pipe system
(2) Light hazard or ordinary hazard occupancy
(3) 20 ft (6.1 m) maximum ceiling height
(4) No unprotected ceiling pockets as allowed by 8.6.7 and
8.8.7 exceeding 32 ft2 (3.0 m2)
(5) No unprotected areas above cloud ceilings as allowed by
8.15.24

Jesse

7/25/2023 08:31:01 am

I'm confused by the statement

However, it's not an Ordinary Hazard area, it's a Miscellaneous storage area that is equivalent to an OH2 curve.

OH 2 is Ordinary Hazard. There really isn't anything just Ordinary Hazard. Its either Ordinary Hazard Group 1 or 2.

Pete H

7/25/2023 12:43:17 pm

Similar to the code itself, "ordinary hazard" can be used as a generalized term when it is either ordinary hazard group 1 or 2, and whichever it is isn't actually important to the discussion.

As seen in NFPA 13 (2016) 11.2.3.2.3.1(2) - Light hazard or ordinary hazard occupancy.

Dan Wilder

7/25/2023 08:37:56 am

As long as you're not in the 2002 edition (Sept 2010 #4 Tech Notes NFSA), the QR area reduction is applicable and to give Pete some backup. It is not as clear in the more current versions from digging around a bit.

From the 2016 handbook excerpt:

13.2.2
The most popular modifier from Chapter 11 is the reduction in the design area (based on the ceiling height) for the use of quick-response sprinklers. This reduction is not allowed for storage protected in accordance with Chapter 12 or any of the requirements in Chapter 14 through Chapter 21, but the reduction is allowed for miscellaneous storage and low-piled storage based on 13.2.2. Any of the adjustments that apply to ordinary or extra hazard occupancies under Chapter 11 also apply to the corresponding miscellaneous or low-piled storage. This adjustment includes the 30 percent increase to the design area for steep ceiling slope (greater than 2:12 or 16.7 percent), which is not permitted to be used with other types of storage but is allowed to protect storage covered under Chapter 13.

Franck

7/25/2023 10:05:55 am

Yes you can
Storage below 12 ft (class I-III) is not considered as storage, but as ordinary hazard occupancy (whether it is is miscelaneous or pure storage does not matter).
All reductions apply.
Note that you can also have a slope at ceiling gretaer than 17% and apply the 30% area penalty (while it is not allowed to have a 17% slope at ceiling if height is above 12 ft).

But to be honest, for a new project and if your water supply allows it, I won't do it. This will give you margin for possible future changes of commodity classification (use of plastic containers, for example).

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Use QR Reduction for Miscellaneous Storage?

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