Single-Speed vs Variable-Speed Furnace Blowers
Outdated PSC (permanent split capacitor) blowers standard in many older furnaces incorporate a low-tech motor that consumes substantial energy and offers only one operating speed. When the furnace burner cycles on, the blower runs at 100% output. When the burner turns off — the blower completely shuts down, too. On/off air circulation presents a number of performance and efficiency drawbacks:
- PSC furnace blowers consume as much as 400 to 600 watts of electricity per hour of operation.
- Indoor temperatures swing considerably, spiking above the thermostat setting when the blower turns on, blasting rooms with hot air. When the blower cycles off, cessation of air circulation causes room temperatures to plunge below the thermostat setting.
- The on/off noise of high volume air roaring in the ductwork is often distracting.
- Excess air volume stirs up dust and degrades indoor air quality. In addition, when the system cycles off, air filtration also ceases as circulation through the filter is interrupted.
Technology now provides a better option for furnace blowers. A variable-speed ECM (electronically commutated motor) blower runs almost continuously at lower output, adjusting speed and air volume to match heating requirements. This advanced air circulation is superior in several ways:
- A variable-speed blower consumes only about 75 watts of electricity per hour. Because the electrical expense associated with the blower is a substantial contributor to the cost of heating, upgrading to an ECM blower can reduce monthly heating expenses.
- ECM variable-speed furnace blowers are programmable. Speed ramps up to reach the thermostat setting, then gradually drops back down to lower output to maintain the temperature to accurate tolerances. This virtually eliminates noticeable temperature swings.
- Because air circulation is continuous, air filtration is also ongoing at all times.
- Variable-speed ECM blowers incur less wear and tear and last longer than on/off single-speed units.