This strikes me as overthinking run amok. I'm surprised it made it through to the final document. Is the logic that the area/density method requires flowing over the entire area? Thus, if your area is smaller than the required area you have a choice: use room design method, or add this phantom flow.
Mark A. Sornsin, P.E. | Karges-Faulconbridge, Inc. | Fire Protection Engineer | Fargo, ND | direct: 701.552.9905 | mobile: 701.371.5759 | http://www.kfiengineers.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Cahill, Christopher Sent: Wednesday, March 13, 2013 4:46 PM To: [email protected] Subject: Phantom Flow Not what you think by the subject. Working out of NFPA 13 '13 23.4.4.1.1.5. This is new and confusing us greatly. I have a 20,000 sq.ft. heated LH building. And a 2,000 sq.ft. area that needs a dry system. Not an auxiliary dry system. My starting required design is 0.1/3,900. I calc the system at 2,000 sq.ft. (cuz that's all I have) and get for discussion sake 220 gpm. Then I subtract from 390 (3,900 x 0.1 per 23.4.4.1.1.5) and I get 170 gpm. Then I go back to the calc and redo but this time I add 170 at the end of the main. Now this has the effect of overflowing all the rest of the BL's such my final calc is more than 390. !@#$^# What if I have a 500 sq.ft. building and the next building is 20 miles away @#$@# are we calc'ing this extra area for? Can someone 'splain if we got it right and then why in the world this got into the standard? Chris Cahill, PE* Senior Fire Protection Engineer, Aviation & Facilities Group Burns & McDonnell 8201 Norman Center Drive Bloomington, MN 55437 Phone: 952.656.3652 Fax: 952.229.2923 [email protected]<mailto:[email protected]> www.burnsmcd.com<http://www.burnsmcd.com/> Proud to be one of FORTUNE's 100 Best Companies to Work For *Registered in: MN _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
