I believe they put that section in the code to deal with a code logic error that gets made when applying the obstruction rules. (2007 edition referenced) If you had a 4'-0" obstruction against the wall with 18" of clearance, generally people would try and make you put sprinkler heads underneath it because spray does not reach both sides of the obstruction. They try and apply 8.6.5.1.2 (b) or 8.6.5.1.2. The error occurs when they reference 8.6.5. Which should not be applied because of 8.5.5.2 & 8.5.5.3. 8.5.5.2 only applies to obstructions within the 18" plane and tells you to go to 8.6. The correct section to apply would be 8.5.5.3. As far as the water on the floor, what you seeing makes a lot of sense to me. I never understood why if its open on top everything is fine. If its solid up to the ceiling/deck, somehow the area doesnt get enough water. Which shouldnt really happen, because the sprinkler head cannot spray underneath the obstruction no matter if it's open above or solid, so it's just the "pooling" effect that reaches the hazard.
-----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Brad Casterline Sent: Tuesday, July 22, 2014 3:49 PM To: [email protected] Subject: RE: stepped obstructions Thanks Jeremy. I'll have to study this a little more this evening. I was wondering what difference that top 18" makes, whether open or closed off, then it is further complicated by SC or EC! I also measured the Accumulated Mass Per Unit Area of water on the floor and, when open at the top (4' wide projection) there was a very slightly less amount of water on the floor, which makes sense, but is negligible. -----Original Message----- From: Jeremy Frazier [mailto:[email protected]] Sent: Tuesday, July 22, 2014 1:23 PM To: [email protected] Subject: RE: stepped obstructions No thats not a typo, new section added in 2013. If you look in your obstructions, near the start of the section where they talk about 4'-0" rule, obstruction against the wall rule. -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Brad Casterline Sent: Tuesday, July 22, 2014 2:11 PM To: [email protected] Subject: RE: stepped obstructions Well I modeled open on top and closed at the top and got no difference in activation time or extinguishment time, with standard coverage pendent. Then I looked at 13-2013 FIGURE A.8.8.5.1.2 (bottom of page 338 in the handbook), the extended coverage counterpart of FIGURE 8.6.5.1.2, and saw "No additional protection required when 2 ft or less"!! (For standard coverage it is 4 ft or less). Is there a typo somewhere? Brad Casterline -----Original Message----- From: Brad Casterline [mailto:[email protected]] Sent: Tuesday, July 22, 2014 8:27 AM To: [email protected] Subject: RE: stepped obstructions 4' if the fascia does not extend up to the ceiling, but stops a minimum of 18" below the ceiling, hence called a projection, otherwise 2'!! The difference between 13-2013 FIGURE 8.6.5.1.2(c) and FIGURE 8.6.5.1.2 (top of page 309 in the Handbook) is a real head scratcher. There is not much one can do, other than model it with hope of ANY additional insight. Brad Casterline -----Original Message----- From: Cahill, Christopher [mailto:[email protected]] Sent: Tuesday, July 22, 2014 7:04 AM To: [email protected] Subject: RE: stepped obstructions I think you are OK without the sprinkler in the lowest soffit. But I'm not sure it's because of that section from the upper most head. Perhaps from the lower head in the higher soffit. I always thought the section while saying protected really is/was an area that wouldn't get water there but was OK because it was small. Look at the latest edition too. I think you can get up to 4' wide now with soffits without heads under them in some circumstances and 2' in other. Chris Cahill, PE* Associate Fire Protection Engineer Burns & McDonnell Phone: 952.656.3652 Fax: 952.229.2923 [email protected] www.burnsmcd.com *Registered in: MN Proud to be #14 on FORTUNE's 2014 List of 100 Best Companies to Work For -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Todd - Work Sent: Monday, July 21, 2014 4:04 PM To: [email protected] Subject: stepped obstructions I have a situation where I have a stepped obstruction against a wall. The occupancy is Light Hazard. The primary ceiling is 9'. There is a 4' wide soffit against a wall that is 1' lower. Under that soffit, there is one that is 1'-10" wide that sticks down an additional 1'. I presently have a sprinkler in the high area that is 3'-2" from the edge of the higher soffit. A sprinkler is going to be required under the under the first soffit because the sprinkler in the high area cannot protect underneath it based on section 8.6.5.1.2(1) (NFPA 13 - 2002). However, the sprinkler in the high area can protect under the lower soffit per section 8.6.5.1.2(3). Can I install a sprinkler under the upper soffit and call it a day? Todd G Williams, PE Fire Protection Design/Consulting Stonington, CT www.fpdc.com 860-535-2080 (ofc) _______________________________________________ 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 _______________________________________________ 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 ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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