sprinklernotes Cloud Ceilings and Different K-factor Sprinklers “For an open area in an education facility, there are cloud ceilings installed that will require sprinkler protection below. Is it permissible to utilize K-11.2 EC sprinklers above the clouds and K-8.0 EC sprinklers below the clouds?”
We have reviewed NFPA 13, Standard for the Installation of Sprinkler Systems, 2019 edition as the applicable standard. Our informal interpretation is that the use of different K-factors is permitted in this scenario. Section 27.2.4.9.2 prohibits the mixing of sprinklers to minimize discharge: 27.2.4.9.2 Unless the requirements of 27.2.4.9.3 or 27.2.4.9.4 are met, mixing of sprinklers of different K-factors by reducing the K-factor of adjacent sprinklers on the same branch line leading back to the main for the purpose of minimizing sprinkler over discharge shall not be permitted. While the different K-factor sprinklers are adjacent on the same branch line, it is not for the purpose of minimizing over discharge. Only the overhead sprinklers or the sprinklers installed in the clouds would be included in a single design area, so there would be no mixing of K-factors in the hydraulic calculation. As long as all of the sprinklers installed in the clouds are the same K-factor, they would be permitted to be different from the overhead sprinklers. Additionally, Section 27.2.4.9.4 explicitly permits an allowance for extended coverage sprinklers with different K-factors as long as they are installed per their listing.
