ESFR design area with only two branch lines

[skdesigner]

I imagine this has been asked and answered before, but I must be using the wrong combo of keywords in my search.

I have a small storage room where ESFR sprinkler protection will be required in order to avoid in-rack sprinklers. It is a very narrow room, such that it can be protected with two rows of sprinklers. All of the adjacent areas are Ordinary Hazard, protected with standard spray sprinklers. In this unique scenario - what would be the correct design area for the ESFR sprinklers?

 

[UFT12]

I take it the area protected by ESFR sprinklers is enclosed and separated from the remainder area by walls. My sense follows the standpipes principle, that is, if I don't have 4 standpipes to reach 1000 gpm I do not include more connections. Similarly, if I wouldn't have 3 branch lines I would not include more ESFRS and therefore I would include only 4 on each of the 2 branch lines. Of course an AHJ could think otherwise.

 

[TravisMack]

You may want to look at the "phantom flow" provisions that were put in the standard starting with the 2013 editions. That provision is based on area/density design, so not sure it would fully comply, but that would be my first thought. That is assuming the room in question does not meet the rating for room design methods.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com

 

[skdesigner]

Thanks so much for the suggestions. Both make sense. I'm just hoping to avoid calculating 6 heads on 2 lines.

 

[TravisMack]

I think 6 sprinklers on 2 lines would be massive overkill and more than the intent of the standard for that type of protection. I would probably do 2 lines with 4 sprinklers and just add the phantom flow at the cross main. Hopefully the AHJ could see reason with that and not require the 2x6 calc.

Travis Mack, SET, CWBSP, RME-G, CFPS
MFP Design, a Ferguson Enterprise

http://www.mfpdesign.com

 

[skdesigner]

Thanks Travis, I fully agree!

 

[UFT12]

One could say that the ESFR sprinklers should get activated somewhat faster due the limited space that does not allow the heat to travel far at the lateral direction to the branches hence more heat remains above the fire and around the 2 x 4 sprinklers. Just a thought.