The flow of return air ensures that air circulating through your home is properly filtered as well as heated or cooled to meet the thermostat setting. A central HVAC system actually comprises two distinct types of airflow and ductwork: supply and return. In operation, the total system forms a continuous circular airflow flowing from supply to return and back to supply.
How Return Air Flows
Supply air flows through supply ducts directly from the AC or furnace and enters rooms through the supply vent. Return air, conversely, flows in the opposite direction in separate ductwork, leaving rooms through individual return vents—or a single large vent typically located in a central hallway—and returning air back to the central air handler.
While supply air pressure is positive, the return airflow system is under negative pressure generated by the system blower. Here’s the basic path that air follows through returns:
- Air is pulled into individual return vents, which are typically not adjustable and remain open at all times.
- Airflow through dedicated return ductwork reaches the indoor air handler, where it is pulled through the system air filter.
- Return airflow is either reheated or cooled as it passes through either the furnace heat exchanger or the air-conditioner evaporator coil, respectively.
- As the filtered, conditioned return flow is pulled through the blower, it becomes supply air again. Pressure of the airflow is positive, as it is forced through supply ductwork into individual rooms.
Preventing Problems
Problems in the return system can impact indoor comfort, healthy air quality, and system efficiency. To keep system airflow moving in the right direction, keep these factors in mind:
- Make sure all return vents in rooms are unobstructed by any objects such as furniture, drapes, etc.
- Change the system air filter at least every other month.
- Have ducts inspected for air leakage that reduces return flow.
- Schedule annual preventative maintenance with your HVAC contractor.
For regular preventative maintenance—or professional repair—to keep return air flowing in your home, call Mowery Heating, Cooling and Plumbing.
