Your home’s central HVAC system incorporates two separate types of airflow: supply air and return air. While supply air is moving from the furnace or the AC through ductwork into rooms, return air is removed from rooms via separate ductwork. Though the consistent flow of supply air tends to be more noticeable, return airflow is also a critical factor that supports optimum heating and cooling efficiency, as well as a healthy indoor environment.  

How Return Air Flows

Return air is removed from rooms and “returned” to the central air handler to be cooled or heated again. In some cases, a return vent is located inside each individual room. This vent is typically not adjustable, nor can it be manually closed. Alternatively, the home may have one large central return vent typically located in a hallway. Return ductwork is under negative pressure from the blower that’s located in the central air handler. The path of airflow proceeds as follows:

• Return air is pulled into ductwork under negative pressure from the system blower.
• Return air passes through the air filter, which is located at the air handler. This is the point where irritating and toxic airborne particulates are removed from the home environment.
• Clean return air is drawn through the AC evaporator coil for cooling or through the furnace heat exchanger to be heated.  
• After passing through the blower, system airflow is now under positive pressure.
• Filtered, conditioned air is pushed through supply ducts into all rooms.

What Can Go Wrong

Because the flow of air in your HVAC system is a circle, any problem in the system potentially affects both supply and return airflow. Factors that may affect return air specifically include:

• Anything obstructing the return vent in individual rooms or the central vent. This could be furniture, drapes, or other objects.  
• Leakage in return ductwork at joints between segments or due to internal corrosion.
• A dirty or clogged air filter.
• A worn-out blower that does not move sufficient airflow. 

For professional advice about issues that may affect the flow of return air, contact Powers Heating & Air.