When the Comfort Plus system receives a heat call from the room thermostat or forced air zone control panel, the supply air blower is signaled to operate at one of multiple air delivery volumes (CFM). The unit monitors the discharge air temperature and runs the core blower(s) to extract heat from the brick core and the variable speed blower delivers it to the appropriate heating zone through the ductwork.
The variable speed motor adjusts motor speed to achieve the appropriate air volume (CFM) for the thermostat input(s) received. The maximum CFM required is selected at the Variable Speed Motor Interface Board during installation. The Variable Speed Motor Troubleshooting topic describes when each specific CFM is targeted based on the various calls from the thermostat.