I can't believe I'm asking this question after all these years. Anyway, swallowing pride and asking.
2010 NFPA 13 strict Density/Area method 11.2.3.2 and 22.4.4.1.1. Great big room being subdivided. Existing system with a new wall added between heads on a BL. Contractor had to add a head on one side to preserve the existing spacing (area) of the heads. Without head over 130 sq.ft. I take the 1.2 ^.5 of the area and get 46.5' required along the BL. Original system lets say calc'd 5 heads on the BL. But now in the same 46.5' there are 6 heads on the BL. Do I ignore the wall and require a new calc? What if the wall is rated 1 hour do I ignore it? I looked all over and can't seem to find anything definitive. Room design is out so not a consideration. 22.4.4.1.1.1 simply says all the heads in the 46.5'. I can't find anything that says either to count the wall as a break so measure 46.5' from the wall in each direction and still see if there are 5 head or ignore it and there are now 6 heads. I find 11.1.2 that clarifies to extend the density or not. I don't think that's applicable exactly. The question is not about whether to extend the density on either side. Let's just say it's all OH. It gets a little more complex as on the one side of the wall they cut a head in on the BL but on the other side there is a perpendicular new wall and they come off same BL and arm over to two more head so if I ignore the walls there are now 8 heads off the 1 BL. Prefer a code section or written reference 'cuz this is going to be a big deal if we ignore the walls. Ordinarily with unrated walls they are ignored in density/area (of course can't find that reference). I think I'm getting tripped up with the rated portion? Or maybe I'm just tired???? Chris Cahill, PE* Associate Fire Protection Engineer Burns & McDonnell Phone: 952.656.3652 Fax: 952.229.2923 [email protected]<mailto:[email protected]> www.burnsmcd.com<http://www.burnsmcd.com/> *Registered in: MN Proud to be #14 on FORTUNE's 2014 List of 100 Best Companies to Work For _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
