Greg,
A couple of thoughts come to mind for me.
First, I would regard the large circular duct as similar to
unobstructed construction. The location of the deflector of the
sprinklers below the duct would have to be as called out in 8.12.4.1.
So, for those purposes the position below the duct would be driven by
the k-factor you're using.
Second, the use of an ESFR system to protect LH/OH occupancies is
allowed by 12.6.7.1, provided that the original design was per the
criteria in chapters 12 through 20. I don't think the manufacturers are
going to stand behind designing ESFR's to meet obstruction rules for
standard spray sprinklers. To my way of thinking the continuous
obstruction rules of 8.12.5.3.1 would still be applicable. I don't
agree that it would be possible to eliminate the concern over
obstructions less than 48" wide, as items (3) and (4) of that section
suggest 24" is the cutoff width.
I don't know if that's correct, however those are my initial thoughts.
*Ken Wagoner, SET
*Parsley Consulting***
*350 West 9th Avenue, Suite 206
*Escondido, California 92025
*****Phone 760-745-6181*
Visit our website <http://www.parsleyconsulting.com/>
***
On 09/02/2015 2:18 PM, Gregg Fontes wrote:
Looking at a building that has ESFR fire sprinkler protection. Half is being used as open office area.
They are installing circular ducts from 32" to 84" diameter with the top of the duct
approximately 36" below the ESFR deflector (right below the roof trusses). In reading 8.12.5.3
2013 edition, in most cases if not all, Table 8.12.5.1.1 cannot be met, so sprinklers will need to be
installed under the ducts. With the duct being 32" to 84" diameter, where would the fire
sprinkler be placed? Per NFPA 13 is a flat barrier required to be installed under the circular duct? FM
give you a guideline, but 13 does not. Owner does not want the ESFR sprinklers change out, so again
where would you place the sprinkler and/or is a flat barrier required by NFPA 13? (With a flat
obstruction you can either be under it or within so many inches of the end, but a huge diameter
obstruction, is it the edge, center ,etc.?)
Second thought, since this is no longer a storage application, can you apply the
standard spray sprinkler obstruction rules? (This still does not state where to
install the sprinkler below the obstruction, but you could eliminate the obstruction
less than 48".)
Thanks,
Gregg Fontes
Cen-Cal Fire Systems, Inc.
209-334-9119
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