The PA404 is a series 40 (2-wire, SPST) pressure controller for use in 24, 120, 240 or 277 volt control circuits or in self powered (millivoltage) applications.
- The PA404A is a pressure actuated high limit, safety control for steam heating boilers, it breaks an electrical circuit to shut down the burner if steam pressure rises above a safe level
- The PA404B is used with suspension-type unit heaters to make the fan circuit when a pressure rise indicates the presence of steam
- Each model contains an SPST microns switch snap acting switch
- Sensitive pressure actuated diaphragm expands or contracts with pressure variations, moving a lever mechanism which operates the snap switch
- A screw on top of the case allows set point adjustments without removing the cover
- Differential is adjusted by means of a dial located inside the case