Vacuum Switch for Napoleon Pellet Stove NPI40/45, NPS40/45, TPS & TPI35 Part Number: W660-0056
The vacuum switch is the stoves way of knowing it has an airflow through the venting in the proper direction. If the vacuum switch doesn’t see a pressure difference it will not remain closed. When it opens the auger is stopped depriving the stove of fuel and leading to shutdown.