What Does the Return on an Air Conditioner Do?

Airflow

• Central home cooling systems supply cooled air through an air transfer system that runs throughout a house. This system converts, or conditions, the air in a home by removing heat and humidity from the air. Air transfer systems consist of a supply side and a return side. The supply side includes the vents that deliver conditioned air into the rooms of the house. The return side sends air back to the air handler to remove any existing heat or humidity buildup.

Duct Systems

• The duct systems within a home provide pathways for air to move from one part of a house to another. Duct systems come in different types depending on the kinds of materials that make up the ducts in a system. Metal ducts consist of galvanized steel shaped in a round or rectangular form. Metal ducts wrapped in insulation materials work well in terms of reducing air leaks. Flexible ducts consist of round, accordion-like tubes that contain plastic linings wrapped in insulation material. Rigid ducts or ductboard consists of foil-covered, rectangular passages with fiberglass linings. In effect, the type of duct system installed affects how well the air return system on an air conditioner works.

Return Air Transfers

• It's not uncommon for a home to have supply vents in each room, but only one return air vent in a centrally located room. In cases where air in a room, or a set of rooms, is blocked off from the remainder of the house, the return air vent has to make up for the loss of air contained in these rooms. Over time, ductwork systems can develop leaks in areas where tape adhesives have deteriorated and caulked areas have worn away. When this happens, the return duct will pull air through leaks or gaps in the ductwork to compensate for the lost air supplies. Oftentimes, this “pulled” air comes from basements, attics or crawl space areas. As a result, a cooling system has to work harder to supply conditioned air within the home’s living area.

Effects

• The return air vent on a central cooling system is designed to function within a closed air system. A system with no leaks in the ductwork operates as a closed air system. This means the air handler actually “reconditions” air that comes in through the return air vents. In cases where leaks appear in the ductwork, return vents have to pull air from attics and basements, meaning the intended closed air system no longer exists. When this happens, homeowners end up paying more in cooling costs since the system has to work harder to condition the non-conditioned air coming from attic and basement areas. In some cases, the extra work may actually overload a home’s cooling system, meaning living areas remain humid or muggy while the air conditioner is running.