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We have a project with ESFR sprinklers near a roof deck and a large, round fabric duct (similar to "DuctSox") that is below the ESFR sprinkler. The round duct is as large as 6-foot diameter on one end, and gets down to as small as 3'-3" diameter on the opposite end (the run of duct is ~140 feet long).
The duct is almost perfectly centered horizontally between two ESFR sprinkler rows, and it is also located 6'-8" vertically below the sprinkler deflectors. Is this duct considered an obstruction that would require sprinklers underneath? Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
9 Comments
Mike
4/1/2020 11:08:44 am
Best read NFPA 13, 2016 8.12 and manufacturers data sheet. ESFR's have very strict obstruction guidelines. I have had to put extra heads beneath 6" roof drain piping.
Jesse
4/1/2020 11:13:47 am
Without seeing it, it's tough but I would err on the side of it being an obstruction. ESFR obstruction rules are very stringent. My guess is the fabric would interfere with the continuity of the water cone and cone development.
Wes
4/1/2020 11:24:43 am
NFPA 13 8.12.5.3.1 has allowances for obstructions to ESFR sprinklers, but these only allow continuous obstructions up to 2-feet wide.
John
4/1/2020 12:07:30 pm
We have amended our local code and use section 8.12.5.1.2. in NFPA 13 (2013 Ed.) Since this is a collapsible duct and placed in the center of the sprinkler lines we require the HVAC unit that supplies the air movement to shut down during a water flow alarm. Similar to the requirements for the High volume, low speed fans Section A.8.12.5.2.
James
4/1/2020 12:09:28 pm
This is great - and a very similar application to HVLS fans. Even without a local code amendment, that approach could be proposed to the AHJ under NFPA 13 Section 1.5 as an approved alternative approach. 4/2/2020 02:34:19 pm
That was my proposal as well, engineer of record did not agree with the idea.
Peter I
5/1/2020 10:24:27 am
I had a similar situation with fabric duct where extending sprinklers to cover the area below the duct would be cumbersome due to the arrangement of system/space. We ended up requesting AHU shutdown upon activation of a VESDA detection serving this space.
Nick
4/6/2020 09:42:27 am
According to NFPA 13 2016 Section 8.12.6, the clearance between the deflector and the top of storage is 36 in. Could you not reason that the spray of the sprinkler would be fully developed in relation to the duct (which is over 6'-8" below the deflector) and therefore would not be considered an obstruction? After all, one does not take into account obstruction rules with storage.
John Lane
4/13/2020 10:09:25 am
At greater than 48" it is still an obstruction even though it is 6'-8" below the sprinkler heads. A herd duct would require a head underneath, however with a cloth duct this would be difficult. Leave a Reply. |
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