Series RFS-4000 is a line of general purpose proving switches designed for HVAC and Energy Management applications. These switches can be used to sense positive, negative, or differential air pressure. The plated housing encloses a diaphragm, a snap-acting switch, and an optional calibration spring (in adjustable set point models). The sample line connections located on each side of the diaphragm accept rigid or flexible tubing. Various electrical connections are available. An optional enclosure cover can be provided to protect the operator from accidental contact with the live switch contacts. The enclosure cover has five knockouts for a 1⁄2″ conduit connection