Protection under soffit

[jkampana]

I am doing NFPA 13 system in a senior housing project. The living quarters are a residential light hazard occupancy. I want to make sure I am designing these rooms correctly.

The heating ducts will be ran below the floor joists then box around creating a soffit on one side of the room. In the main living room the soffit 15" wide x 24" deep. another is 33" x 12" and another 15" x 12". If I am reading NFPA correctly I will have to have a pendent sprinkler installed under that soffit if it projects away for the wall more than 8"(8.10.7.1.5.1)? Is this correct and if not would I use figure 8.10.6.1.2(b) for the soffits under 30" wide? What then is the ruling for soffits wider than 30"?

Thanks in Advance.

 

[TravisMack]

Are you protecting the area with sidewalls or pendent sprinklers? If pendent, get far enough away from the soffits and you good. If using HSW, then you need a pendant under the soffit.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[jkampana]

First floor will have pendents and the second level will have sidewalls.

So on the level where pendents are used I would use Figure 8.10.6.1.2(b) to determine the distance I would need to be away from the soffit correct? What do I do in instances where 'D' is greater than 30"? Id assume put another head beneath the soffit.

 

[TravisMack]

Use the beam rule for soffits >30" in width.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[jkampana]

Thank you for your help Travis.

The soffit in question is 33" wide and 12" deep. According to the beam rule in 8.10.6.1 and table 8.10.6.1.2 I would have to be 7' from the side of the obstruction making me 9'-9" from the wall. and there is a notch in the room near the door greated by the outcropping of a closet. It wouldnt even be possible to get that far away from the soffit. What then is the procedure? Head under the soffit also?

 

[TravisMack]

Yes. If you can't space sprinklers to throw under obstructions, then you need to place a sprinkler under the obstruction.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[cdafd]

Agree with travis' last post

If you can get water on the floor you are good to go

Sounds like it would be easier to position heads so water gets to the wall at floor level