What is the air pressure requirement for single interlock preaction systems?
NFPA 13 requires that sprinkler piping and fire detection devices for preaction systems must be automatically supervised where there are more than 20 sprinklers on the system. The air pressure is only provided to ensure the overall integrity of the piping system. NFPA makes no stipulation for minimum air pressure requirements for single interlock preaction systems for two reasons: 1. Since a single interlock preaction system is considered a “wet” system, there will be adequate water pressure at the sprinkler to ensure proper sprinkler operation. 2. The loss of pressurized air does not take part in the operation of the deluge valve. Therefore, low air pressures, as little as 2 psi, may be used for sprinkler piping supervision. This can be accomplished through the use of the Reliable Model B Air Compressor Panel, or, where a source of pressurized air is provided, with the Model C Air Maintenance Device.
