QR vs Res Sprks

[mx272]

Can anybody explain why in NFPA 13 you can use either QR or Res Sprks in a residential (light hzd) facility and in 13R you can only use Res Sprks (there is an exception in 13R to use QR's if no more that 4 sprk in a unit). Any thoughts would be appreciated.

 

[sfallows]

they allow you to use either qr or residential sprinklers just that you use the appropriate density.


most space listing for residential sprinklers will have a density of .05 gpm/sq ft

example


tyco TY2234 20x20 20 GPM (75,7 LPM) 16.7 psi (1,15 bar)

PDF:

http://tyco-fire.com/TD_TFP/TFP/TFP400_01_2006.pdf

so this head covers 400 sq ft with 20 gpm flow, which works out to .05 gpm per sq ft and if you wanted to use it for light hazard you would need to have a density of .1

I hope this helps

 

[firepe]

Residential heads and NFPA 13R are designed with survivability in mind, personal safety, as opposed to property conservation as the main focus as in NFPA 13.

As Tindey alludes to, there is a definite density difference between 13 and 13R. There is also the "wall wetting" ability of the head. Wall wetting is the performance objective with residential style heads, and not so much with standard spray quick response heads.

So while the fusible elements may be the same or similar in response time, the actual performance of the head is different. NFPA 13R limits us to just 4 QR heads, as previously stated, and NFPA 13 mandates that the density be 0.10 for residential heads to "compensate" for the performance objective" differences.

 

[firepe]

As a second follow up,

Yes, you can use QR heads in NFPA 13 as well as residential heads, but at the cost of a larger design area and more heads in the design area, than that required when using residential heads in a residential application.

The NFPA 13 residential design requirement is 4 heads regardless of walls for design, while the QR design could be largest room, or more likely an area/density design. In addition, there is no hose allowance required for residential design, while a hose allowance is likely required for a QR design.

There, hope that was clear as mud.