Use 4-Sprinkler Residential Calc in Highrise?

5/31/2022

Have a design criteria question;

I am using Tyco LFII k4.9 sprinklers in a residential renovation for a 20-story highrise. Mostly light hazard, non-combustible building structure. The building does have commercial offices, but the floors being renovated are all completely residential.

Based on a design density of 0.10 gpm/sqft, would I need to abide by the 1,500 sqft remote area size for Light Hazard from NFPA 13, or by the product data from Tyco stating the 4 most demanding sprinklers?

This is falling under the 2013 Edition of NFPA 13, not NFPA 13R of course.

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6 Comments

Alex

5/31/2022 07:08:47 am

Hi,

NFPA 13 (2013) 11.3.1 outlines the special design approaches for residential sprinklers. 11.3.1.1 states that the design area must include the four adjacent sprinklers that produce the greatest hydraulic demand.

Note, you still need to calculate the corridor per NFPA 13.

Thanks,
Alex

Todd E Wyatt

5/31/2022 08:25:00 am

I recommend reviewing the applicable, adopted Building Code (e.g. 2021 IBC) as it pertains to automatic sprinkler systems (ASPS) in high-rise buildings (HRB).

Per 2021 IBC 403.3 Automatic Sprinkler System, ASPS requirements in HRB include a secondary water supply. For HRB >420 feet (probably not applicable in your case), there are additional requirements relating to number of sprinkler risers and to fire pumps.

Patrick Drumm

5/31/2022 08:31:50 am

Another item that may be sometimes overlooked. Confirm that you are flowing the 4 heads according to Note C from Table A in the sprinkler's product data sheet.

"For NFPA 13 residential applications, the greater of 0.1 gpm/ft2 over the design area or the flow in accordance with the criteria in this table must be used."

Jesse

5/31/2022 08:34:32 am

While the building does fall under full 13, NFPA 13 gives you latitude for a 4 sprinkler calc. in 2016 NFPA 13 11.3.1. However, because the full version of 13 still governs, you'll need to remember that the common areas such as lobby, corridors, etc still need to be calc'd Light Hazard.

Eric R

5/31/2022 09:17:33 am

Everyone has things pretty much covered this morning, so I'll just add emphasis on a few things.

From Alex's post: When selecting the 4 most demanding sprinklers you disregard walls, and base it solely on the piping arrangement. This is different from NFPA 13R where you would follow the room layout for picking adjacent sprinklers.

From Patrick's post: Paying attention to both demand requirements really comes into play with sidewall sprinklers, especially if you are using a model that has higher demands if the sprinkler is lower than 6" from the ceiling.

For my own 2 cents: Most brands now have a residential sprinkler line that comes with 5.8K orifices. Unless the residential rooms are all pretty small you will get better design characteristics upsizing from the 4.9K heads due to the 0.1 density requirement for NFPA 13 systems.

Christopher Anderson

6/2/2022 03:46:56 pm

I agree with the comments above and would also recommend that the scope section of 13R be reviewed. Those clauses clarify the building types where NFPA 13R is applicable.

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Use 4-Sprinkler Residential Calc in Highrise?

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