In a forced air system, there are two main types of blower motors, a PSC and ECM. PSC (permanent split-capacitor motors) were the norm, and if your furnace pre-dates 2009, it probably has one. An ECM (electronically commutated motor) is typically found in newer furnaces with an AFUE (Annual Fuel Utilization Efficiency) of 95 percent or higher.

A PSC motor runs only at full speed, so any time that the blower is on, it blows the air at full force. Because they always run at full speed, they are not the most efficient. PSC motors are louder than an ECM motor; and, unless properly adjusted by a professional, they may not be providing optimal airflow within the proper range of external static pressure. For instance, higher static rates result in lower airflows, and since a PSC motor cannot adjust speed or torque, its performance drops off.

An ECM motor is a variable speed unit based on direct current design. This makes the ECM motor more efficient than the alternating current-designed PSC motor, resulting in much lower operating costs for the year. Unlike standard blower motors, ECM motor technology provides continuous and gradual fan speed changes. The result is optimized humidity control, dramatically reduced sound levels, and greater comfort.

With an ECM motor, air is circulated for longer periods of time compared to a standard PSC motor, but at a fraction of the cost. The results are reduced air stratification while making your home more comfortable. Because ECM motors are more efficient, they may also qualify for government and/or manufacturer rebates.


If you would like to learn more about what furnace is best suited for your situation, contact the professionals at Langton Mechanical.