I hate to state the obvious, nor sound like a d....e, but it's because it os the rule. It's the same if I have a duct that is 48" wide I need to place sprinklers under the duct but i can have multiple ducts 47" wide with a gap 1" wide between them, and I can have then all across the room and don't have to sprinkler under them. So at some point you have to look at common practice and you'd never see my scenario. What about yours? Do you regularly run into 2' 11" and 3' 1" stems?
On Thu, Apr 28, 2016 at 3:02 PM, Larry Keeping <[email protected]> wrote: > It may be of help if you reference the 2016 edition of NFPA 13. > > There, in Section 8.6.4.1.2(5) the 3 ft limit has been deleted. > > The Committee Statement for that revision was that concrete tees are > capable of withstanding the heat long enough for sprinklers to activate > even when the tees are closer than 3 feet on centers. > > Larry Keeping > > -----Original Message----- > From: Sprinklerforum [mailto: > [email protected]] On Behalf Of > [email protected] > Sent: April-28-16 5:35 PM > To: [email protected] > Subject: NFPA 13 (2013) 8.6.4.1.2(5) - why the 3ft minimum? > > Forum, > > We have concrete tee construction. Bottom of stems measured from the > ceiling is 26" down. Centerline of stems are spaced apart in an every > other fashion of 7', 2'8", 7', 2'8", etc. Ideally we would like to use > NFPA 13 (2013) 8.6.4.1.2(5) to protect the area so we don't have to add > additional sprinklers/piping. However it states this is only applicable > for 3ft to 7.5ft stem spacing. Can someone tell me the purpose behind the > 3ft minimum threshold? Even though we have some 2'8" sections, do you > believe the intent of this code was for my situation? Or do you believe > the intent is for concrete tee construction where every stem is 3ft or > less? I can see people interpreting this passage either way as all stems > are spaced away from another stem more than 3ft, yet all stems are spaced > away from another stem less than 3ft. > > To me, it seems ridiculous that I can have stems with any depth (let's say > 10ft) and spaced 3'1" apart and the deflector can be located 1" below the > bottom of the stem (10'1") and branchlines can be spaced 15ft apart. Yet > if the same depth stems are spaced 2'11" apart the deflector can't be lower > than 22" below the ceiling and because they are now obstructed, they have > to be in every pocket. > > I appreciate anyone's opinion on my situation and/or knowledge/history of > this codes development. > > Note: As I allude to, I know there are other ways to design this system > utilizing 22" and beam rule. I am more looking for the "Why's" or the "You > missed this blurb" that agrees with your stance . > > Thanks, > Sean VG > > > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > -- Ron Greenman 4110 Olson Dr., NW Gig Harbor, WA 98335 [email protected] 253.576.9700 A problem well stated is a problem half solved. -Charles F. Kettering, inventor and engineer (1876-1958) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
