An annual airflow check verifies that the heating and cooling system delivers design airflow rates through the evaporator coil and ductwork, measured in cubic feet per minute (CFM). Proper airflow ensures optimal heat transfer, prevents coil freezing, and maintains rated system capacity. Standard practice targets 350-400 CFM per ton of cooling capacity. Technicians measure airflow using anemometers, manometers, or calculation methods based on external static pressure.
Technical Details
Direct airflow measurement involves handheld anemometers positioned across return and supply ducts. Indirect measurement uses external static pressure readings compared against blower performance curves. A system rated for 3 tons should deliver approximately 1050-1200 CFM. Airflow restrictions from dirty filters, blocked ducts, or coil fouling reduce efficiency by 5-15% and decrease capacity. Proper airflow verification requires stabilized system operation at full load.
Practical Significance
Restricted airflow is the leading cause of evaporator coil freezing and reduced system performance. Annual airflow checks identify filter clogging, duct obstruction, and blower degradation early. Maintaining proper airflow improves comfort, efficiency, and system longevity while preventing premature coil failures.