Approximately 400 CFM per ton is commonly used as an initial design reference for many ducted HVAC applications.

However, it should not be treated as a fixed rule for every heat pump or project. The final airflow should follow the selected equipment's blower-performance data and the actual building requirements.

What does 400 CFM per ton mean?

Using the common initial reference, a 3 Ton system may be around 1,200 CFM, a 4 Ton system around 1,600 CFM and a 5 Ton system around 2,000 CFM.

Actual design airflow can vary depending on equipment and operating conditions.

Why can airflow vary?

Cooling load, sensible and latent load, indoor humidity, coil performance, duct resistance and manufacturer requirements can all affect the optimum airflow.

Why is room-by-room airflow important?

Total air-handler airflow must ultimately be distributed to individual rooms. Each room should receive airflow according to its cooling or heating requirement, rather than simply dividing the total airflow equally.