NFPA 13 with Residential Sprinklers

[mattyd723]

NFPA 13 (2013) Figure 11.3.1.1(a) has always seemed ambiguous to me because it does not consider how the sprinkler heads are fed. What do they mean by adjacent in 11.3.1.1? Adjacent with respect to fire areas or adjacent on a branch line? I wrestle with this one frequently. Please have a look at the picture:

Riddle me this: which 4 heads are considered adjacent? A+BCD or A+XYZ?
A+BCD would have a higher demand, but are the heads considered adjacent?
A+XYZ are more likely considered adjacent (in my opinion), but they won't necessarily produce a higher demand.
Which ones would you calculate?

Thanks,
Matt

 

[TravisMack]

I would run a calc for both to size and just base my system on the most demanding.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[mattyd723]

Thanks for the input, TravisMack. I suppose that is the safe way to go, but is it the required way?
The question I'm really looking to address here is: What do they mean by adjacent in 11.3.1.1? Adjacent with respect to the piping or adjacent with respect to compartments, walls & openings?

 

[stookeyfpe]

I've always interpreted that Section 11.3.1.3 (2010 edition) dictates that both areas be calculated and the most demanding area be used as the basis for design. In many cases one will employ residential sprinklers with extended coverage. These sprinklers can produce higher demand when greater areas of coverage/sprinkler are called out by the designer.

 

[TravisMack]

In NFPA 13, we are directed to choose a remote area that will "go through walls," unless using the room design method. For that reasoning, my understanding is to go with heads A,B,C & D as they will have the highest demand, provided that all heads have the same minimum pressures.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com