SINGLE INTERLOCK PREACTION (Type A)

A Single Interlock Preaction Type A system, as defined in EN 12845, is a fire protection system designed to provide both reliability and protection against accidental discharge. It operates primarily as an electrically actuated single-interlock system, where detection by an electric fire detection system energizes a solenoid valve to release the preaction valve, allowing water into the sprinkler piping only upon confirmed fire detection. However, EN 12845 requires Type A systems to function even in the event of a power failure. This fail-safe capability is achieved through the integration of a dry pilot actuator connected to the system piping and the valves pressure chamber. Under normal conditions, this actuator remains closed while the solenoid valve controls the system electrically.

If power is lost, a secondary solenoid valve opens, allowing communication of the dry pilot actuator with the system piping. Should a sprinkler open due to fire, air pressure will be vented from the system piping, opening the actuator, venting the valves pressure chamber, allowing for the preaction valve to open, ensuring water delivery despite the power loss. This design prevents inadvertent operation from isolated sprinkler or pipe damage when power and backup systems are intact yet guarantees valve operation during electrical faults or power failure. Thus, the Type A preaction system provides both enhanced reliability and continuity of protection, automatically defaulting to a dry-pipe system mode under loss of power.