Question 1: Look at A.8.5.4.1. (07 ed) The channels are filled with insulation so the bottom of the insulation becomes the new ceiling for you point of measurement in determining the distance between the deflector and the ceiling. Though not stated, it stands to reason that the construction category for the assembly would also apply the presence of insulation and call it unobstructed.
Question 2 Look at 8.15.1.2.17 (2010 ed). This is a new allowance that addresses just this scenario. It also finally addresses the obvious need for an air gap just below the roof assembly ( allows up to 2 inches). It also identifies that a non- or limited-combustible facing material must cover the bottom of the chords. Then no sprinklers above the drop ceiling (assuming no other combustible materials exist). Unfortunately, this new allowance in chap 8 was never submitted to the TC on Discharge for Chap 11 so no TC guidance on whether the 3,000 sf applies. Seems one should be able to apply the Equivalency clause without to much trouble (other than being at the mercy of someone else having to decide acceptance). Roland On Oct 23, 2009, at 8:55 AM, Steve Leyton wrote: > I'm pretty sure I know the answers to these already, but client just > called and they're in a meeting with an AHJ right now, trying to > negotiate the basis of design on a project that has been dragged out > by > differing interpretations of the standard. The building contains > multiple conditions where 22" and 30" TJI's are present, with > insulation > in the channels and batts installed such that the bottom of the > insulation is resting on the lower chords. There is a suspended > ceiling > below that in many areas: > > 1) If the insulation creates a smooth continuous surface, it can be > considered as a ceiling and deflector distances below the TJI's can be > measured down from the batts as a "smooth ceiling condition", thus > exceeding the 22" threshold below the deck for obstructed > construction, > yes? > > 2) This condition requires a 3,000 SF design area for unprotected > combustible concealed spaces, as there is no ceiling attached directly > to the underside of the TJI's - just insulation. The 3,000 SF design > area applies to both above and below the suspended ceilings, yes? > > Thanks, > > Steve Leyton > Protection Design & Consulting > San Diego, CA > > > > > > __________ Information from ESET NOD32 Antivirus, version of virus > signature database 4536 (20091023) __________ > > The message was checked by ESET NOD32 Antivirus. > > http://www.eset.com > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email to:[email protected] > (Put the word unsubscribe in the subject field) > _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
