A pressure switch is often referred to as a vacuum switch. This sensor is looking for airflow within the stove to close the circuit to the feed system and the igniter. If your stove is feeding pellets, your pressure switch is ok. For the switch to work properly, the hopper and the front door must be making a tight seal. Almost all of the time, the switch is good but there is an air leak or point of failure somewhere else within the stove. For example, a clogged vent or burnt-out combustion blower motor.

This switch is calibrated to close the ignition and feed circuit at .10 WC PF.