Beyer Boys Logo

Airflow 101: How It Works

Airflow 101: How It WorksIf you’ve ever called a qualified professional HVAC technician to diagnose a problem with your air conditioner or furnace, you may have noticed that system airflow is among the very first things he or she checks. This single parameter reveals a great deal about the condition of the system and points the way to possible problems.

Your central HVAC system is divided into two distinct segments that move air:

Supply Air

Heated or cooled air leaving the air handler flows through dedicated supply ducts to individual rooms. The exact volume of air moving through the ducts is carefully calibrated to match the output of the furnace or A/C and the square footage of the house.

Return Air

Air is drawn out of rooms through the return grille—or through a single central grille usually located in a hallway—then conveyed through the dedicated return ductwork back to the central air handler where it is filtered, then heated or cooled again. Airflow then re-enters the supply ducts.

Problems related to the flow of conditioned air include:

  • Clogged filter. A dirty air filter is a common cause of insufficient airflow. Filters should be changed at least every other month.
  • Air imbalance. A balanced system means air volume entering a room through supply ducts equals the volume removed through return ducts. Positive pressure means supply air entering a room exceeds the rate of return air being removed. Negative pressure is the opposite: return air is being drawn out of the room faster than supply air is entering. An unbalanced system can cause inconsistent heating and cooling performance, higher operating costs and also degrade indoor air quality.
  • Ductwork isssues. Residential ductwork often develops leaks that worsen over time. Conditioned air may leak out of ducts into zones such as the attic, crawl space or inside wall voids. Duct leakage wastes energy as a furnace or A/C runs longer cycles to compensate. It also unbalances the system airflow and may allow unfiltered or contaminated air to enter rooms.

For professional service to diagnose and correct potential HVAC airflow problems, contact Beyer Boys.