When the inducer motor runs and reaches the specified vacuum

If the box is warped

protecting your damper hardware from premature failure

As a non-positional relay

Rheem-Ruud AP13147 Damper Assembly Freon When the inducer motor runsThe Rheem Ruud AP13147 is a heavy duty 5 inch vent hood damper assembly engineered for induced draft gas water heaters and commercial ventilation systems. This metal constructed damper assembly functions by mechanically regulating airflow, effectively preventing energy robbing backdrafts and ensuring that combustion byproducts like carbon monoxide are safely expelled from the building. Designed for compatibility with 5" diameter Rheem replacement