LF31 Water Heater gas furnace pressure switch 20~200pa, debuggable. LF31 gas furnance air pressure switch senses positive, negative or differential air pressure Includes springs and orifice restrictors Hardware kit included. Electrical rating: 5A/24VAC. Factory set at 50pa. Set point range: 0.10" to 34.0" W.C. Maximum pressure:40"W.C. Contact arrangement: SPDT. Temperature range: -40 to 190 Deg F. gas furnace replacement parts. The molded silicone diaphragm converts very low pressure or vacuum into movement of an actuator disk, which operates the silver alloy contacts