any obstruction tight to the ceiling (or where the top of the obstruction is above the plane of the deflector and of course the bottom of it is below the deflector) including big pipe, must be applied since you have to satisfy 8.6.5.1 BEFORE jumping to 8.6.5.2. So if you are truly in 8.6.5.2, continuous obstructions kick you back to 8.6.5.1 BUT we clarified this issue in the 13 edition since if the top of the duct/big pipe/whatever is 8 inches below the deflector, applying the beam rule is kinda idiotic. So, it now says continuous where the top of the obstruction is level or above the plane of the deflector. If this is not the case, then in LH only structural members are addressed. Naturally there is a caveat. There was a case where an architect didn't like the looks of the sprinkler so placed a hanging light directly below all sprinklers, Literally, this is not a continuous obstruction but since the effect is the same as a continuous obstruction, so the last paragraph of A.8.6.5.2.1.4 was added. One could say that the end of the first paragraph should be deleted since we added the text about the top of the obstruction to 8.6.5.2.1.2 but that wasn't flagged as part of the proposal.
For a shorter version, your designer is closer to being right. Roland Huggins, PE - VP Engineering American Fire Sprinkler Assn. --- Fire Sprinklers Saves Lives Dallas, TX http://www.firesprinkler.org On Jan 22, 2014, at 7:36 AM, "Martinez, Dewayne" <[email protected]> wrote: > NFPA 13 (07ed) section 8.6.5.2.1.8 > > Can we ignore the size of the pipe and not apply the 3 x rule if we are > in a light hazard occupancy (8.6.5.2.1.4)? I have always applied the > rule but one of my designers has questioned me on it. > > Thanks, > > Dewayne > > > > _______________________________________________ > 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
