In NFPA 13, 2007 ,
(2) Installed with the deflectors at or above the bottom of the structural member to a maximum of 22 in. (559 mm) below the ceiling/roof deck where the sprinkler is installed in conformance with 18.104.22.168.2.
Table 22.214.171.124.2 shows different (please see the attached sketch
and give a solution