Use NFPA 13 Table or Product Data for Spacing?

1/17/2023

The maximum allowable protection area for a sprinkler listed is in Table 8.6.2.2.1(a) of NFPA 13 (2016 Edition).

Section 8.5.2.1.1(1)(b) says to choose the larger of twice the distance to the wall, or the distance to the next sprinkler.

Do we use the protection areas in Table 8.6.2.2.1(a) when applying this code section, or do you use the maximum allowable protection area for a sprinkler that's listed in the manufacturer's data?

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9 Comments

Dan Wilder

1/17/2023 07:48:16 am

This is quick answer but a very deep subject, so I'll try to answer as best as I can.

Nearly every standard coverage sprinkler I can think of refers back to NFPA 13 for area maximums. Those areas are defined via 8.5.2.1 for standard coverage sprinklers using A=SxL. As in much of NFPA, as you read deeper into sections, it starts general and becomes more restrictive/specific.

If there is a MFG data sheet indicting a more restrictive maximum area, that must be followed.

8.5.2.1 - General definition (all sprinklers) how to find area of coverage and maximums.
8.6.2.2.1 - Area of Coverage maximums specific to Light Hazard

So, yes, use the Table 8.5.2.1 with 8.6.2.2.1 (a) to establish maximum protection areas based on the criteria to establish the "S" (Distance between sprinklers or 2x the distance to the wall when <7'-6") multiplied by the "L" (Distance between branch lines or 2x the distance to the wall when <7'-6"). In either case, both of those maximum distances will be 15' for Light Hazard (excluding small room rule).

Other sprinkler types and hazards carry their own separate requirements.

Anthony

1/17/2023 08:15:14 am

If the sprinkler is "listed" as a standard spray sprinkler it will have a maximum area a 225sqft. As that is the definition of such a sprinkler.

Anything larger than 225sqft is considered extended coverage and thus falls under the rules of 8.8 and 8.9 (generally).

NFPA 13-16
3.6.4.11.1 Standard Spray Sprinkler. A spray sprinkler with
maximum coverage areas as specified in Sections 8.6 and
8.7 of this standard.

Alex

1/17/2023 10:01:46 am

Anthony said it well!

Jesse

1/17/2023 08:32:09 am

Important to remember, that just because a standard coverage sprinkler is listed for 225-sq. ft coverage - or an Extended Coverage sprinkler is listed for 400 sq. ft. coverage doesn't mean you can space it that far.

Because sprinkler coverage area is an vital component of the area / density calc, (i.e. Sq. Rt of Pressure End Head * K-factor / Coverage Area) you might not have the water supply available to space standard coverage sprinklers at 225 sq. ft.. You might have to go a little less. Its a lot more noticable using EC sprinklers when the data sheet gives you the differing flow parameters based upon coverage, but the same principle holds true for standard coverage sprinklers.

Franck

1/17/2023 10:17:13 am

As a summary, use the manufacturer’s data if maximum coverage area is smaller than the one indicated in Table 8.6.2.2.1(a), as long as the final coverage area is fine with hydraulic calculations, as outlined by Jesse.

As an example, a manufacturer max area for a given sprinkler might be 225 sq ft, but when used in a specific storage arrangement, the final requirement might be 100 sq ft maximum, or even less if the required density ends up with a required pressure from the hydraulic calculation that can’t be supplied by your fire pump.

Jess L.

1/17/2023 10:29:23 am

Read your sprinkler cutsheets. Read your sprinkler cutsheets. Read your sprinkler cutsheets. Read your sprinkler cutsheets.

Bill

2/7/2023 02:40:40 am

So, in say a residential application (light hazard) or in other words 225sq ft max. But the head used is listed for 400sq ft given it has enough pressure and gpm. Assume this head has sufficient supply to spray the listed 400sqft. Do you follow NFPA (225sqft) regardless? Or does the listing supercede the light hazard code?

John

2/7/2023 02:42:03 am

Looking for the answer to this as well.

Wes

2/7/2023 07:52:44 am

Bill, what's the specific sprinkler model? Might be able to help by looking at the cutsheet.

Also, as it's residential, are we under NFPA 13, or NFPA 13R or 13D?

If it's NFPA 13, Residential Sprinklers (under Chapter 12 of NFPA 13 2022 Edition) have Areas of Coverage in accordance with their listing (Section 12.1.6.1). It would be a Residential occupancy hazard classification, not Light Hazard. So if it meets the pressure and flow requirements of the listing at 400 sqft, then it would be compliant with NFPA 13.

That's not necessarily an easy thing to achieve, because 400 sqft with NFPA 13 0.10 gpm/sqft is 40 gpm out of each sprinkler. That's quite a bit to flow for smaller k-factors.

If you're under NFPA 13R or 13D, then that density requirement falls to 0.05 gpm/sqft so you'd only need 20 gpm (400 sqft x 0.05 gpm/sqft) out of each sprinkler. The data sheets usually show tables for 13R and 13D and expect the reader to calculate their own minimum flow if it's a 13 system.

Post a link to the cutsheet and we can chat on this.

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Use NFPA 13 Table or Product Data for Spacing?

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