This topic is covered in NFPA 13 -2022 edition: 28.2.4.7.3* <https://link.nfpa.org/publications/13/2022/annexes/A/groups/28#ID000130009750>
The requirements of 28.2.4.7.1 <https://link.nfpa.org/publications/13/2022/chapters/28#ID000130004847> and 28.2.4.7.1.1 <https://link.nfpa.org/publications/13/2022/chapters/28#ID000130004848> to include every sprinkler in the design area shall not apply where sprinklers are provided above and below obstructions. 28.2.4.7.3.1 Sprinklers under the obstruction shall not be required to be included in the hydraulic calculation of the ceiling sprinklers. ENHANCED CONTENT Collapse The basic idea behind hydraulic calculations, including reasonable safety factors, is to account for all the sprinklers that might open in case of a fire. Where sprinklers are installed both above and below obstructions, all sprinklers above and below the obstructions are unlikely to open. Rather than force the user to calculate both sets of sprinklers simultaneously, the user is directed to prove the most demanding situation with calculations. In most cases, ceiling sprinklers will represent the greatest demand, unless significant numbers of sprinklers are installed under obstructions with long runs of relatively small-diameter pipe. The presence of a permanent or temporary obstruction, such as an overhead garage door, is treated in a manner similar to that for a ceiling configuration that requires sprinklers to be located above and below the ceiling. 28.2.4.7.3.2 Where the piping to sprinklers under obstructions follows the same sizing pattern as the branch lines, no additional hydraulic calculations shall be required for sprinklers under obstructions. ENHANCED CONTENT Collapse The requirement in 28.2.4.7.3.2 clarifies that as long as the pipe sizing under the obstruction is the same as the branch lines, the sprinklers under the obstruction generally will not be more demanding because of the increased elevation head gained dropping down under the obstruction. Care still should be taken, however, where long runs of pipe are utilized to provide protection under an obstruction, where multiple sprinklers are fed off a single drop, and where the drop is a dead-end feed off a gridded overhead system. The 2025 edition of NFPA 13 might have some additional guidance on this issue. The first draft meetings were just held last month, Thanks, John John August Denhardt, PE *Vice President, Engineering and Technical Services* *American Fire Sprinkler Association* m: p: 301-343-1457 214-349-5965 ext 121 w: firesprinkler.org <https://www.facebook.com/firesprinkler.org/> <https://twitter.com/afsa/status/1039528345367732224> <https://www.linkedin.com/company/american-fire-sprinkler-association-afsa-/> <https://www.instagram.com/firesprinklerorg/> *Our members are at the heart of everything we do.* Don’t gamble; attend AFSA41! Click here <https://www.firesprinkler.org/register-for-afsa41/> to view the schedule and register for AFSA41: Convention, Exhibition, and Apprentice Competition at the Bellagio Las Vegas October 16-19, 2022. The regular registration deadline is August 26, 2022. On Tue, Aug 23, 2022 at 3:34 PM Fpdcdesign <[email protected]> wrote: > What I have is an ESFR system where i need to add a single sprinkler in 2 > locations under ducts. 23.4.4.7.3.1 states that sprinklers under > obstructions do not need to be included in hydraulic calculations. > 23.4.4.7.3.2 states that if the sprinklers are under obstructions are piped > with the same size branch piping, additional calculations under > obstructions are not required. I’m assuming that the difference is that > the first one is based on one or two sprinklers under obstructions in > isolated location. The other is if enough sprinklers are installed under > obstructions to create an new calculation area. Neither really address any > restrictions on pipe sizes for sprinklers under obstruction. > > Todd G Williams, PE > Fire Protection Design/Consulting > Stonington, CT > 860-535-2080 (ofc) > 860-554-7054 (fax) > 860-608-4559 (cell) > > > On Aug 23, 2022 at 12:35 PM, <Derrek Crigler <[email protected]>> > wrote: > > NPFA 13 2016 23.4.4.7.3.2 > > > > *From:* Fpdcdesign <[email protected]> > *Sent:* Tuesday, August 23, 2022 9:30 AM > *To:* Discussion list on issues relating to automatic fire sprinklers < > [email protected]> > *Subject:* [Sprinklerforum] Re: Sizing of pipe below obstructions > > > > Brett, any specific reference for that? > > > > > > > On Aug 23, 2022 at 12:21 PM, <Brett Peters <[email protected]>> wrote: > > Typically non storage sprinkler supplied with 1" > > Storage type sprinkler supplied with same size as branch line (typical for > ESFR sprinklers) > > > > Thanks > > > > Brett Peters > > General Manager Installation & Design > > Proudline Fire Protection Services Ltd. > > [email protected] > > 780 490 7602 office ext 202 > > 780 490 7605 fax > > 780 777 0568 cell > > 780 718 2676 24h > > Visit us at www.proudline.ca > > > > Proudline now offers ULc listed monitoring services, please contact > [email protected] for more information > > > > > > > > > > > > > > On Tue, Aug 23, 2022 at 10:09 AM Fpdcdesign <[email protected]> wrote: > > > > > > Todd G Williams, PE > > Fire Protection Design/Consulting > > Stonington, CT > > 860-535-2080 (ofc) > > 860-554-7054 (fax) > > 860-608-4559 (cell) > > > _________________________________________________________ > SprinklerForum mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > To unsubscribe send an email to > [email protected] > > _________________________________________________________ SprinklerForum > mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > To unsubscribe send an email to > [email protected] > > _________________________________________________________ SprinklerForum > mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > To unsubscribe send an email to > [email protected] > > > _________________________________________________________ > SprinklerForum mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > To unsubscribe send an email to > [email protected]
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