Why is adequate airflow across the evaporator essential, and what are common causes of restricted airflow?

• A. Adequate airflow is required for proper heat transfer and to avoid high superheat; causes include dirty filters, dirty evaporator coils, closed or obstructed ducts, and undersized or faulty fans.
• B. Airflow affects only the condenser, not evaporator.
• C. Restricted airflow improves efficiency.
• D. Adequate airflow only affects noise; causes are irrelevant to coils.

Answer: (A)

Adequate airflow across the evaporator is necessary because heat transfer from the room air to the refrigerant inside the evaporator coil depends on moving air. If air flow is restricted, the coil can’t absorb heat efficiently, which lowers cooling performance and often leads to the refrigerant not vaporizing fully. That incomplete evaporation tends to drive the refrigerant leaving the evaporator into a state of higher superheat, putting extra strain on the compressor and reducing system efficiency.

Common causes of restricted airflow include dirty filters, which block air from reaching the coil; dirty evaporator coils, which increase resistance to airflow and reduce heat transfer; closed or obstructed ducts, which physically limit the path for air to reach or leave the coil; and undersized or faulty fans, which can’t move enough air across the coil.

The other options miss the key role of air movement in the evaporator and the real impact of reduced airflow on performance and compressor health, so they don’t fit the scenario as well.