If your pellet stove is failing to light, shutting down unexpectedly, or refusing to run the combustion blower circuit, a failed vacuum pressure switch is one of the first components to check. The Lennox H5889 is the correct OEM-spec replacement switch for Lennox Bella, Winslow PI40, and Winslow PS40 pellet stoves. It monitors negative pressure (draft) produced by the combustion blower and signals the control board that proper airflow is present before allowing the ignition sequence to continue. Sold individually and also cross-referenced as NBK Parts number 20212.
Pellet stoves use a sealed combustion chamber and a dedicated combustion (exhaust) blower to create a controlled draft. The vacuum pressure switch is a safety interlock -- it confirms that the blower is running and generating adequate negative pressure before the control board proceeds with ignition. If the switch fails open, the stove will not light or will fault out immediately. If it fails closed, it can create an unsafe condition by signaling airflow when none is present.
Common symptoms of a failed H5889 switch include a stove that clicks through the start cycle but never ignites, an "air flow" or "draft" fault code on the control board, or a stove that lights briefly and then shuts off. Replacing this low-cost switch is a logical first diagnostic step before condemning the combustion blower motor.
Closes at .10 inches water column (WC PF), matching the factory specification for the Bella, PI40, and PS40 combustion systems.
Designed to drop into the existing switch bracket and hose barb connection on compatible Lennox and Winslow pellet stove models -- no modifications needed.
Prevents ignition when combustion airflow is insufficient, protecting the stove and the flue system from incomplete combustion conditions.
Listed under both Lennox part number H5889 and NBK Parts number 20212, making it easy to verify you have the correct replacement before ordering.