Senasys manufactures a line of firestat adjustable duct limit switches. The adjustable temperature duct limit switch features a helix bi-metal element that senses rapid increases in temperature, such increases often caused by fire in a HVAC duct system. The duct limit switch operates a single pole, single throw (SPST) switch that opens when temperature rises. The adjustable duct limit switch can be set by the operator to sense 100°F to 250°F. The enclosure has an ambient temperature of -40°F to 190°F. And the element’s ambient temperature is 350°F.
The duct limit switch is supplied with a manual reset lever, which requires human intervention to reactivate the limit switch after the high temperature condition has cleared.
Firestat duct limit switches are installed in air ducts to shut down HVAC equipment when air temperature exceeds a pre-set limit. These duct high temperature limits are indispensable in specialized HVAC applications and Building Automation Systems.