Lennox 12L81 SPST Pressure Switch 3.00" WC

The Lennox 12L81 SPST pressure switch serves as an indicator of pressure within the system of air. It works like an SPST switch. Specifically, when air pressure reaches a certain point, which is 3" WC, this switch is activated. Depending on the type of switch, N/O or N/C this will create either an opening or closing of the circuit. Typically, if the pressure drops below this set point, the switch will snap open, and this will result in the cutting off of power to the furnace or air conditioner.