Combining In-Rack and Ceiling Demands
“We are installing in-rack sprinklers in one double-row rack that is 50-ft long
and 8-ft wide. The required ceiling protection for our application is
0.40/3,000. When we balance the in-rack sprinklers with the ceiling sprinklers,
do we need to calculate the entire 3,000 sq. ft. at the roof or can we just
prove the 0.40 over the 400 sq. ft. area of the rack that we are protecting
with in-rack sprinklers?”
We have reviewed NFPA 13, 2016 edition that you indicated as the applicable
standard. Our informal interpretation is the entire ceiling demand is applied.
I can see where there can be some confusion regarding the text in 23.4.5.2:
“Water demand of sprinklers installed in racks shall be added to ceiling
sprinkler water demand over the same protected area at the point of
connection.” This text is attempting to avoid adding the water demand for
in-rack sprinklers to the ceiling demand in a different portion of the
building. It is not attempting to reduce the ceiling demand when over a rack
covering a smaller area than the ceiling remote area. As such, you calculate
your ceiling demand and the in-rack demand separately. You then balance the two
demands to the higher pressure at the point of connection for the in-rack
sprinklers (per Section 23.4.5.3).
The above is a description of the typical process. It should be noted that
there are scenarios whereby the in-rack sprinklers are not combined with the
ceiling demand. For instance, solid shelving where additional face sprinklers
are provided and a higher operating pressure is provided, combing the demand is
not required (see Sections 16.1.6.6 and 17.1.5.7).
ed. (see Sections 16.1.6.6 and 17.1.5.7).
=========
Technical Update is prepared by the Technical Services Dept. of the AFSA:
Roland Huggins, a PE registered in fire protection engineering, Vice President
of Engineering and Technical Services; and Tom Wellen, a PE registered in fire
protection engineering and Tom Noble E.T., a Technical Programs Specialist.
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 2017, American Fire Sprinkler Association. All Rights Reserved.
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.firesprinkler.org/private.cgi/sprinklernotes-firesprinkler.org/attachments/20170313/5a87673d/attachment.htm>
