compartments and calculated heads 1

[GlorifiedPlumber1984]

HELP!

We have been designing and installing 13D and 13R in a variety of townhouse applications, and recently we had a plan reviewer start questioning or most remote/demanding heads. Specifically, its a 4 story townhouse that we received a variance to run it as 13d "modified". All the bells and whistles of nfpa 13R, without the need for a listed fire pump.

We selected the 4 most demanding heads on a floor, and everything was good to go for about 18 of these type units. Now the plan reviewer is saying that we need to use a 4 head calc that involves heads on 2 different levels since the stairwell between floors makes it one giant compartment. In NFPA 13D/13R, we have never had this asked of us. The stairwell is a standard one you would find in a million townhome/single family applications, but now we are at a standstill due to this. We cannot make the system work with the heads he is asking for (2 on the 4th floor, 2 on the 3rd floor), and we already are using a 2hp booster pump, 1 1/2" copper incoming's, low flow 3.0k factor heads spaced at 14 x 14. There is no combination inside the house we can use to make this work without forcing a builder to run 4" incomings and upsizing the pump to ridiculous levels.

The point is, does anyone know of possible ibc/irc or nfpa language that address's this? If he is right, we will figure something out as we don't want to vary from code, but I honestly don't consider seperate floors with 1 small opening between them for the stairs the same compartment.

 

[TravisMack]

A couple things don't seem right. If you calculated 4 sprinklers on 1 floor, then taking 2 on 2 floors should be less demanding. It would be interesting to see your layout.

When things get unusual with an AHJ in things like this, I would go to the basics. Start with the definitions of compartment in 13R. See if that helps your case for using 4 sprinklers in one compartment.

Finally, I have never been asked to calculate the stair as a volume compartment with sprinklers on multiple levels.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

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[MGXFP]

Also too a fundamental idea of fire protection is only to protect one fire at a time in one place.

Modeling two level of fire sprinklers operating simultaneously sure seems more like arson than the type of fire the system is intended to protect.

If nothing else have the builder provide an 8" lintel separating the stairs from adjacent spaces. That should meet the definition of a compartment per chapter 3 and force calculations to be only within the compartment.

 

[GlorifiedPlumber1984]

Thanks all. I probably didn't describe it perfectly, but there is no compartment on floors 3 and 4 that have 4 heads. This is a standard townhouse with a roughly 25 x 15 footprint, and the top two floors are broken up into bedrooms, closets, bathrooms and small hallways. The second floor has a wide open family room so we have a 4 head calc there. We also calced 2 heads on the 3rd and 2 heads on the 4th as those were the most heads in a compartment on each floor. His "theory" is that because the stairs connect to the floors above, then floor 2 and 3 and 4 are a giant compartment.

When we select 2 heads on floor 3 in the hallway, and 2 heads in 4th hallway, we are negative 36% WITH a booster pump.

I guess we could ask the builder to build a lintel and that should be apllicable to the definition of a compartment, but obviously we are trying to avoid this not just for the extra cost on the builder, but to avoid setting a precedent for all future 13R/D calcs going forward in this Jurisdiction.

I saw that the IBC has language that pertains to fire compartments, and vertical openings (along with what size openings can be in place based on the type of floor structure to maintain a fire compartment), but honestly that's a little out of my league without going into an IBC reading wormhole.

Thanks again for the input, hopefully we can find a favorable outcome.

 

[TravisMack]

Based on that theory, tell him that the sprinklers on Level 03 are sprinklers below an obstruction (the floor) and that you only calculate one level of sprinklers when they are placed below obstructions.

If you had a commercial building and had sprinklers under ductwork >48" in width, you would not be calculating the sprinklers below the obstruction.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

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[SprinklerLifer]

The AHJ is, in reality, probably overthinking the situation. It would seem unlikely that a fire would travel up the stairs and activate two sprinklers. However, based on the application of the code, the AHJ is correct. Without some sort of obstruction, such as the lintel, if a fire originates at the base of the stairs, you could get activation on two levels. 13R does require 4, so I think you are in a tough one to win.

That being said, you indicated that you are using 3.0 k-factor sprinklers. Why? For comparison, the Tyco LFII 3.0 only requires 11 GPM, but it requires an end-head pressure of 13.4 at 14x14. The LFII 4.9 k-factor does require 13 GPM, but only at 7 PSI end head and you can increase your spacing to 16x16 at that flow pressure. Your booster pump might have to go from 50 GPM to 60, but I know it would still be able to be 2HP.

Give that s shot and see how it goes.