Duct under sprinkler

[FireFreak08]

Is it possible to put an pendent under and off to the side of a large duct? I would be putting an upright at a higher elevation, dropping the deflector of the pendent just below the bottom of the duct and providing a water shield.

I've done similar things in the past without issues but I'm not sure if the lower head will actually be set off properly if not placed directly under the duct. See attached for my two thoughts

http://files.engineering.com/getfil...4a04-b4c3-dffb2cfe02cf&file=ductsprinkler.png

 

[cdafd]

I do not approve air heads, ( heads stuck out in the air with no heat collector.


AND, I try very hard not to approve pie plates attached to the head.

Heard one theory that the hot gases will possibly go around the pie plate.

Head should be under duct.

 

[FireFreak08]

Yeah I went with under the duct for the similar reason of no place for the heat to collect. I P.E. here mentioned the water sheilds are really intended for rack type systems which makes sense.

 

[cdafd]

have seen an employee of a recognized code consulatant approve pie plates as an alternative.

Like I said I do not like them and try very hard not to approve them, though it seems I have not seen them proposed in a long time.

 

[FFP1]

Pie plates used as "heat collectors" do not work.......they actually make the situation worse by increasing the activation time of the sprinkler heads. This issue has been thoroughly tested and confirmed by FM. Sprinkler heads under ductwork should be located under the duct (in my "opinion" a minimum of 12 in. from the exterior edge, but I do not think this is addressed by NFPA 13). The problem is the draft caused when heat rises around the edge of the ductwork.........the air speed increases and prevents heat accumulation; the same effect which causes problems when pie plates are utilized.

 

[sfallows]

i would agree with under the duct drawing 2