number of sprinkler heads per riser

[crb7]

dear friends,

May you tell me is there any limitation in number of sprinkler heads per riser for multistory buildings? Table 23.7.3.4 in NFPA 13 determine the number of sprinkler heads for branch pipes based on pipe size. Shall we use that table for riser pipe size or we should use the area limitation?
Can we use 1 riser for multistory buildings if the area per floor is less than 52,000 ft but the total area is more than 52,000 ft?

 

[UFT12]

There is no sprinkler amount limitation rather area limitation per system riser. The table you are referring is practically obsolete and should not be used. There are some very few cases where you are allowed to go with pipe schedule. Otherwise new systems must be hydraulically calculated which practically means, as long as you comply with the area limitations you can install as many sprinklers as you need.

As far as concerns your second question, in general the rule goes, if your floors are separated fire areas and your system zoning is made per NFPA 13 (e.g. sectional control valves, check, water flow alarm etc), you can use one system riser for a total area of more than 52000 ft2 as long as each floor remains less than that. Note that I am only talking based on the minimum requirements of NFPA 13. AHJs have the power to apply other measures depending on building size, height etc.

 

[crb7]

Thank u UFT12 for your precious information. What if we have dry system and cant use system zoning?

 

[UFT12]

The criteria for dry pipe systems are totally different. The governing factor here is not the area rather the time limitation for water to reach the least favorable sprinkler. Study the standard, especially chapter 7 (ed.16).

 

[crb7]

thank u so much