CFM (Cubic Feet per Minute) measures the volume of air moving through your HVAC system per minute. It’s the key number for blower sizing, ductwork design, and proper air distribution.
For air conditioning, the rule of thumb is 400 CFM per ton of cooling capacity. A 3-ton AC needs about 1,200 CFM of airflow. Heat pumps target a similar figure. Low CFM causes frozen coils, short cycling, and uneven temperatures.
Common CFM issues we diagnose
- Undersized return ducts starving the blower
- Closed supply vents reducing total airflow
- Clogged filter restricting flow (most common cause)
- Failing blower motor not reaching rated speed
- Damper closed or stuck
CFM is measured with an anemometer at supply registers, or calculated via static pressure measurement at the air handler. A maintenance visit can confirm whether your system is moving the air it’s rated for.
Related: Blower Motor, Static Pressure, Ductwork.
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Right Way Mechanical is a family-owned HVAC contractor serving Wheat Ridge, Arvada, west Denver, and the Colorado foothills.