Not sure I'm following the logic, but I'll give it a shot: First, just because there is an adjustment in sprinkler spacing for the 4:12 slope doesn't mean that adjustment has necessarily negated the effects of the slope in operating the right sprinklers. So both wet and dry sprinkler systems are 'charged' a 30% increase for large sloping ceilings. Now discard the slope issue.
Apparently, the committee feels it is warranted to 'charge' a dry system design an additional 30% in area (as compared to wet systems) because of the delay in getting water to the open sprinklers in dry systems. Makes sense to me. So whatever you came up with for a wet system design area, if you have a dry system, add 30% to the area. E.g.: if your wet system area happens to be 1,950 (perhaps because you have a steep slope) then add 30% to that number to get the dry system area. You seem to be uncomfortable with the lack of QR reduction allowed for a dry attic system under a steep slope. 200% area increase from a wet system (with QR reduction benefits) to a dry system (that doesn't get the QR reduction). Maybe you have a point- maybe the QR heads would open more quickly and contribute to fire control faster than standard link heads. OR... Maybe we have a situation similar to high-piled storage: in that situation we don't allow QR because we're afraid too many heads will open duet o the high heat release rate. But you notice we don't offer a larger design area as an option. Similarly, maybe the issue of heat by-passing sprinklers as it climbs the slope of the attic ceiling may lead to too many QR heads operating away from the fire. So the committee prefers that we ignore the QR reduction in this case. Another way to look at it is that the QR reduction is a little 'scandalous.' Not everyone agrees it is a good idea, even on wet systems (e.g. FM Global). So for the committee to allow it on dry systems may be considered 'going too far.' They'd rather have what amounts to be a 200% area increase in a fire scenario (steeply sloped attics) that has proven to be a challenge for standard system layouts to control. Or maybe it just hasn't been considered in detail. Maybe some fire testing is in order to prove your point that the design area discrepancy seems excessive. Anyone got some money to sponsor a fire test? Mark A. Sornsin, PE| Fire Protection Engineer Ulteig Engineers, Inc.| Fargo, NDÂ [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Brad Casterline Sent: Monday, February 07, 2011 11:51 AM To: [email protected] Subject: a glaring inequality in 13? I would appreciate thoughts and comments from all willing to take the time: Combustible attic, 4/12 slope, 10' to peak. 1500*1.3=1950 for slope exceeds 2/12. Light Hazard, so QR heads required. If DRY, 1950*1.3=2535. If WET, 1950*.6=1170. (QR Reduction). Doesn't this mean the area has to be increased over 200% for DRY, not 30%? For 20' to the peak, 1950*.75=1463~~ 170% increase for DRY. Using SSU, the increase would be for the exact same spacing and height in both cases. BB and SD Attic heads 'increase' the area 30% for DRY (from 5 to 7 heads), but without regard to height, and the slope MUST be minimum 4/12. They must be within 6" each side of the peak, at 6' max. SSU also have to be within 6" each side, and 8' max is cheaper than a pump. I know this has not come up in the 16 months since I discovered the Forum. If it did before that, I would appreciate being pointed to the location of all discussion about it. Many thanks, Brad _______________________________________________ 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)
