400 CFM per ton is useful—until it isn’t.

In this episode, Bryan and Ty take on one of the trade’s favorite rules of thumb. It can be a reasonable starting point for many systems under moderate, near-sea-level conditions, but it is not a universal target. Proper airflow depends on actual delivered capacity, sensible and latent load, air density, climate, manufacturer data, and what the system is supposed to accomplish—not just the tonnage stamped on the cabinet.

They explain why dry-climate and high-altitude applications may require more volume airflow, why humid applications often use less coil airflow to improve moisture removal, and why mass flow matters more than volume alone. They also cover nominal versus actual capacity, suction-line pressure drop, equipment-specific performance at 208 V, Manual S and expanded performance data, and field verification with measureQuick and the TrueFlow® Grid.

The takeaway is simple: use the rule as scaffolding, then measure the system and follow the equipment data.

This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, NAVAC, and Filtrete.

Resources:

• Not All CFM Are Created Equal
• Impacts of Decreasing Evaporator Airflow
• Troubleshooting With DTD
• AHRI Data vs. Manufacturer Expanded Performance Data
• Bypass Dehumidification Airflow Design
• HVAC School calculators
• Submit a podcast question
• Learn about the GRIT Foundation

Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.