Which of the following statements best describes the evaporator airflow requirement for residential AC?

• A. 300-400 cfm
• B. 350-450 cfm
• C. 400-500 cfm
• D. 200-300 cfm

Answer: (B)

Evaporator airflow is sized to deliver around 400 CFM for each ton of cooling. For a residential AC, that means the airflow through the evaporator should typically be in the 350–450 CFM per ton range. This target balances heat transfer and moisture removal: enough air velocity to carry away the heat absorbed by the refrigerant while allowing enough contact time for the coil to dehumidify the air. If airflow falls well below this range, the coil can be starved of air, reducing heat transfer, increasing run time, and risking frost on the coil. If airflow goes well above this range, the air moves too quickly to pick up much moisture, diminishing latent cooling and overall comfort. Therefore, the 350–450 CFM per ton window aligns with standard design practice, making it the best choice.