How do you properly size an air compressor for a dry pipe sprinkler system as well as for a double interlock preaction system?
NFPA 13 states that a compressor must have a capacity capable of restoring the required system pressure within 30 minutes, except for refrigerated spaces maintained below -5 deg. F, in which case the time requirement becomes 60 minutes. To properly size the compressor to meet these requirements, one must calculate the volume or capacity of the entire sprinkler piping system in cubic feet. Once this is known, the horsepower of the compressor may be chosen based on the cubic feet per minute of compressed air it provides. To determine the volume limitations stipulated by NFPA 13 for these systems, the total piping volume must be converted from cubic feet to gallons (1 ft3 = 7.48 gal.).
