Fellow forumites, I guess I need to back up and expand my comments a little. When I said that I agree with Mark, I was trying to say that if what Mark described in his comments about the head spacing (which none of us know for sure except John) was accurate, and the pendant heads indeed provided adequate coverage for the EH occupancy, then I believe that the sidewall heads should not adversely affect the coverage for the room.
I had envisioned a fairly small room with 4 to 6 heads at the lower ceiling and the ceiling pocket being something like an 8 x 12 area above the table. (The problem is, since we don't have a "picture" of what John is describing, it could be a 3000 sf room with a small ceiling pocket). If it is similar to what I envisioned, this seems like a case where 13 can't possibly cover ever known scenario and some sound engineering judgment needs to be made. (Which I can't actually do since I am not an engineer and don't play one on TV). Maybe someone on the forum with a modeling program could get the actual layout from John, run a model and let us know what the results are. Cliff Whitfield, SET Fire Design, Inc. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Thursday, April 17, 2008 1:11 PM To: [email protected] Subject: RE: Extra Hazard Ceiling Pockets The fire plume knows it is being generated by an EH event and acts differently when it comes into contact with the sprinkler? I don't think so. So what is the issue when you attempt to use a sidewall for EH? 1. Failure to respond at all - NO 2. Responding differently - MAYBE since the ceiling jet flow characteristics for the sidewall position could be different than the upight/pendent position. 3. Delivering too little water - NO, the discharge rate is easily controlled. 4. The discharge pattern from a sidewall cannot control an EH fire no matter how close the sprinkler is or how much water it discharges - Don't know this answer. 5. NFPA 13 says no - Definitely YES. 6. Responding too late because the position of the fire can be farther from the sidewall sprinkler than any EH 100 sq ft or 130 sq ft spacing - YES if the basis for the prohibition is the EH fire is liable to grow too big too fast for the sidewalls to keep up. I think you would have to show a comparable response and comparable discharge characteristics between the sidewall position and the ceiling position. I don't think you can have an OH design in the middle of the room and a EH design on the perimeter. Bill Brooks William N. Brooks, P.E. Brooks Fire Protection Engineering Inc. 372 Wilett Drive Severna Park, MD 21146 410-544-3620 Phone 410-544-3032 FAX 412-400-6528 Cell -------- Original Message -------- Subject: RE: Extra Hazard Ceiling Pockets From: "Cliff Whitfield" <[EMAIL PROTECTED]> Date: Thu, April 17, 2008 1:02 pm To: <[email protected]> John, I agree with Mark. The one thing I would add is that until the last issue of 13, sidewalls under overhead doors were not specifically addressed and I still don't think they are "listed" for that application. It may be a valid point of discussion for the exception when you are talking with the AHJ. Cliff Whitfield, SET Fire Design, Inc. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Sornsin Sent: Thursday, April 17, 2008 11:50 AM To: [email protected] Subject: RE: Extra Hazard Ceiling Pockets You seem to be stating that the pendant sprinklers at the lower ceiling are spaced to cover the entire floor area; the sprinklers in the ceiling pockets are essentially in place ONLY because the pocket doesn't meet any of the criteria in NFPA 13 for omitting sprinklers within. Their coverage of the floor below over-laps the coverage from the pendants. Under that scenario, I would argue that the sprinklers in the lower ceiling should adequately protect the hazard. The sidewalls in the ceiling pockets with reduce any delay in sprinkler operation due to the pockets and essentially provide "extra water" to the floor area below. If your calculations can support full flow of the design area, plus the sprinklers in the ceiling pockets, it seems that you should be fine. But this will require buy-in from the AHJ. The sidewall sprinklers are still not listed for Extra Hazard. This could result in a ruling against using the sidewalls for the sole reason that "the standard says so" - and so it may not matter if the arrangement will work. Mark A. Sornsin, PE Fire Protection Engineer Ulteig Engineers, Inc. Fargo, ND 701.280.8591 [EMAIL PROTECTED] -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Thursday, April 17, 2008 8:09 AM To: [email protected] Subject: Extra Hazard Ceiling Pockets Forum, Let me know what you guys think about this situation. I have a college lab building where the AHJ bumped us up to Extra Hazard Occupancy in the Basement due to storage of flamabile liquids. The labs in the basement have a 3 foot deep ceiling pocket above the experiment table in the center of the room. We spaced pendents at extra hazard spacing throughout the room at the lower ceiling level. We then added two sidewall sprinklers in the ceiling pocket itself. The question as arisen whether we can use sidewalls because the room is to be designed at extra hazard. My therory was that the floor level is protected to extra hazard from the pendents and the sidewalls are only protecting the ceiling pock itself and not the room below. Does anyone agree/disagree with my reasoning. 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