What is a Furnace Blower Motor?
Once your furnace has heated the air within it, the blower motor is responsible for turning a fan to circulate that warm air out of the furnace and into your home. It's up to this device to ensure that your home reaches the temperature set on your thermostat.
Blower motors work in one of two ways: as single-speed or variable speed blower motors.
Single-speed motors turn on when the thermostat indicates the interior temperature has dropped and turn off when that temperature has been reached. Because they operate at only one speed, these motors are using the maximum amount of energy when turned on.
A variable speed blower motor, however, moves at different speeds to better control the flow of air throughout your home. Furnace manufacturers say that these variable speed motors provide better energy efficiency because they are able to operate at lower speeds when appropriate, thereby consuming less energy than single-speed motors. In addition, by operating at a low speed for long intervals, these motors are more frequently circulating the air in your home than their single-speed counterparts and preventing cold spots. Operating at this low speed also helps to minimize the unit's noise.
Types of Motors
You also might see furnace manufacturers advertising permanent split-capacitor (PSC) motors versus electronically commutated motors (ECM). ECMs are used primarily in variable speed furnaces as they are controlled by a microprocessor within the unit that signals as to how much heat is needed. ECM motors, which are comparatively new to the scene having been introduced in the 1980s, are more efficient than PSC motors, even when used in single-speed applications, according to HVAC technicians.
HVAC technicians say that one of the first indicators that your blower motor is in need of maintenance is that your furnace is running non-stop while your house remains cool. This happens because the air is being warmed by the furnace but not dispersed into your home. To prevent such problems, regular maintenance is important. If your furnace has a PSC motor, a licensed contractor should regularly lubricate the blower motor with oil ensures that the fan is able to turn easily (ECM motors use ball bearings and therefore require little or no oiling). Consult your furnace owner's manual for directions on properly oiling your blower motor and other maintenance suggestions.