Description
The Lochinvar & A.O. Smith 100308926 Air Pressure Switch senses negative air pressure generated by the inducer motor and closes its electrical contacts when the draft reaches -1.75 inches of water column, confirming adequate combustion airflow before ignition proceeds. It stays closed as long as sufficient draft is maintained through the heat exchanger and flue passage. Within condensing boiler and warm-air HVAC systems, it mounts at the inducer outlet or pressure tap port, connecting to the control board through spade terminals without additional hardware. At each startup call, it delivers a verified pressure signal that prevents ignition under inadequate draft conditions, safeguarding the combustion circuit.
