Lennox 34M74 Pressure Switch SPST 0.33" WC

The Lennox 34M74-is a SPST pressure switch used in Lennox HVAC products. It serves as a safety device since it measures air pressure within the system and responds electrically in an on/off manner when the pressure gets to a certain level. For the 34M74, this level is normally 0.33 inch WC. With a stable compression rate coming from the Lennox 34M74, the pressure switch also protects the other parts of the HVAC system within from being damaged by pressure changes. For example, a pressure drop may be due to a blocked air filter or a faulty blower fan, while high pressure may be undue stress on the system.