American Fire Sprinkler Association
12750 Merit Dr., Suite 350 * Dallas TX 75251
Ph: (214) 349-5965 Fax: (214) 276-0908
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TECHNICAL UPDATE
FEBRUARY 18, 2009
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How do you approach a hydraulic remote design area where the branch
line is of insufficient distance to meet the 1.2 length?
We have reviewed NFPA 13, 2007 Edition as the applicable standard. Our
informal interpretation is that there are two basic requirements in
establishing the design area configuration. The first size is 1500 sq.
ft., etc., and the other is 1.2 times the selected design area to
establish a rectangular design area. The base requirement is that the
design area must be met.
Section 22.4.4.1.1.3 explains how to address deign areas where the
branch lines are not long enough to satisfy the 1.2 requirement. As an
example, lets consider a building that is 39 feet wide and 100 feet
long with purlins running perpendicular to the 39-foot dimension. The
head spacing on the branch lines are at 13 ft on center and 10 ft on
center between the lines on a side-feed crossmain. There will be 3
heads on each branch line. The selected design area is 1500 sq. ft.
The requirement of 1.2 times the square root of 1500 results in 46.48
ft that cannot be met. The design area of 1500 sq. ft. still must be
met which will require going down the crossmain picking up additional
branch lines. This will require traveling a minimum of 38.46 ft (1500
divided by 39) which in this scenario will require five branch lines.
An example of this scenario is given in Figure A.22.4.4.1 (a) System D.
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Technical Update is prepared by the Technical Services Dept. of the
AFSA: Vice President of Engineering and Technical Services Roland
Huggins, a PE registered in fire protection engineering; Phill Brown,
a NICET IV certified automatic sprinkler technician and NFPA Certified
Fire Protection Specialist (CFPS) and Tom Wellen, a degreed fire
protection engineering technologist. This is provided with the
understanding that the AFSA assumes no liability for this opinion or
actions taken on it and they are not to be considered the official
position of the NFPA or its technical committees.
Copyright ⌐ 2009, American Fire Sprinkler Association. All Rights
Reserved
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