If the standard specifies that we don't have to calculate both complements when the obstruction is as narrow as 4'-1", I have a hard time imagining what would be the basis for a concurrent calculation where the obstruction is (generally) much larger. There's going to be a lot more heat moving past sprinklers below narrower obstructions than if they were installed on a 20' or 30 or wider cloud. I agree with your premise entirely, that flexible joints or unique conditions below the clouds could make them more demanding - that's what I said too. And yes, perhaps some will operate above and some below, based on leakage of byproduct and heat through and around clouds to the deck above, not to the extent that you have concurrent operation of two full design areas. Why would we put them under anything over 4' wide and not calc' those concurrently too?
Now I would go the extra mile and say no reduction of the design area for QR, just to be on the safe side ... Steve Leyton Protection Design & Consulting San Diego, CA -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Todd Williams Sent: Friday, February 06, 2009 4:29 PM To: [email protected] Subject: RE: CEILING CLOUDS - AGAIN Steve, I'm not sure I agree. Aside from what the book says, I look at this type of situation and I have a couple issues with it. Sprinklers at the deck are typically uprights directly off a branch line (or perhaps a short sprig). The pendent sprinklers may be fed by swing joints or flexible drops, which could make those sprinklers more hydraulically demanding. This could make the area below the clouds the most hydraulically demanding. However, I can't say if the ceiling jets on a cloud would be sufficient to activate sprinklers below them without the possibly activating sprinkler above. Without fire tests or other research to verify different, I would assume that some combination of sprinklers at the deck and below the cloud would operate. Since we are charged by NFPA 13 with calculating the most hydraulically remote area, my conclusion is that both levels would have to be calculated to conservatively predict what would actually happen. Typically, sprinklers below obstructions over 4 ft tend to be relatively widely spaced and be relatively small compared to the ceiling area. This may not necessarily hold true for ceiling clouds, especially given the arrangements I have seen. The dynamics of the clouds could be very different than that of a few sections of ductwork. We need some research and testing and hopefully it will happen before a significant fire loss. Todd At 06:51 PM 2/6/2009, you wrote: >Do not concur. If the cloud condition is such that your best judgment >is to provide a complete complement of sprinklers above, then you would >calculate either above or below the clouds, as we always have for >obstructions like ducts and in accordance with the exception spelled out >in 22.4.4.6.3 (2007 ed.). We often use SSP's above clouds and EC's >below, especially when existing sprinklered buildings are being >re-modeled or there's tenant turnover in an office shell, so sometimes >it's two separate calc' areas but not a concurrent calculation of two >different complements of sprinklers. > > >Steve Leyton >Protection Design & Consulting >San Diego, CA > > > > >-----Original Message----- >From: [email protected] >[mailto:[email protected]] On Behalf Of >[email protected] >Sent: Friday, February 06, 2009 2:21 PM >To: [email protected] >Subject: Re: CEILING CLOUDS - AGAIN > >And calculate both levels of sprinklers. You have no idea what is really >going to happen on a fire. > > >Sent from my Verizon Wireless BlackBerry > >-----Original Message----- >From: "Jeff Hewitt" <[email protected]> > >Date: Fri, 6 Feb 2009 16:07:37 >To: <[email protected]> >Subject: RE: CEILING CLOUDS - AGAIN > > >Travis, > >Since we have no specific guidance on this topic, my recommendation is >that >you must protect to deck first, and deal with the obstructions second. > >With this criteria, I would recommend both above and below the clouds. > >Just my thoughts > >Jeff Hewitt, PE, SET, SFPE (Professional Member) >Corporate Engineer >241 Hughes Lane >St. Charles, MO 63301 > >636-946-0011 >636-946-5172 (fax) >314-574-6989 (cell) > >Fire Sprinklers Save lives. >Can You Live Without Them? > >-----Original Message----- >From: [email protected] >[mailto:[email protected]] On Behalf Of Travis >Mack, >SET >Sent: Friday, February 06, 2009 3:50 PM >To: [email protected] >Subject: CEILING CLOUDS - AGAIN > >I have a project with lots of floating clouds. The clouds slope with >the >roof deck and are 1' below the roof deck. If I place a sprinkler in the >cloud, is one req'd in the space above the cloud? I would normally put >sprinklers above the clouds, but with the deflector already at 12" below >the >roof deck based on the cloud height, do you really need the sprinklers >above >the clouds? > >Please feel free to call if you have any questions or comments. > >Travis Mack, SET > <mailto:[email protected]> >_______________________________________________ >Sprinklerforum mailing list >http://lists.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 >http://lists.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) > > >__________ Information from ESET NOD32 Antivirus, version of virus >signature database 3834 (20090206) __________ > >The message was checked by ESET NOD32 Antivirus. > >http://www.eset.com > > > >__________ Information from ESET NOD32 Antivirus, version of virus >signature database 3835 (20090206) __________ > >The message was checked by ESET NOD32 Antivirus. > >http://www.eset.com > >_______________________________________________ >Sprinklerforum mailing list >http://lists.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) Todd G. Williams, PE Fire Protection Design/Consulting Stonington, Connecticut www.fpdc.com 860.535.2080 _______________________________________________ Sprinklerforum mailing list http://lists.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) __________ Information from ESET NOD32 Antivirus, version of virus signature database 3835 (20090206) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com _______________________________________________ Sprinklerforum mailing list http://lists.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)
