The United Electric J21K-15979 Differential Pressure Switch 61-0418 is an electromechanical safety and monitoring device designed to detect pressure differences in HVAC and refrigeration systems. It uses sealed metal bellows to sense pressure variations between two sources and activates an electrical switch when the preset pressure threshold is reached. Common applications include chi... https://www.partshnc.com/united-electric-j21k-15979-differential-pressure-switch-61-0418