Two Stage Furnace Operation

Identification

• According to Frigidaire, a two-stage furnace operates like two separate furnaces. The unit's variable-speed motor keeps it in the first operating stage about 80 percent of the time. During the first stage of operation, the furnace runs at about 68 percent of its total capacity, according to heating and cooling product manufacturer Hayes Heating. A two-stage only goes into the second operating stage when the temperatures drop and additional power is needed to adequately heat a home.

Benefits

• Two-stage furnaces decrease the occurrence of high-to-low temperature swings, Lennox explains on its website. According to Frigidaire, the temperature difference between the first and second stage of operation is just "a couple of degrees." Hayes Heating, a heating and cooling product retailer, notes that because two-stage furnaces operate in the first stage most of the time, they are quieter overall than traditional furnaces. The more consistent airflow of a two-stage furnace results in improved air quality.

Features

• Two-stage furnace models can come equipped with additional features that improve their operating efficiency. For example, you can buy a two-stage furnace with a low-speed fan that provides a continuous flow of warm air, or a secondary heat exchanger that captures additional heat to increase energy efficiency. Because a two-stage furnace runs at different speeds, it provides a controlled flow of warm and cool air in the home. This results in "enhanced humidity control," according to Lennox's website.

Considerations

• Lennox notes that some two-stage furnace models can be combined with electric heat pumps. This gives homeowners the option of switching between gas and electric heat as desired, and can further reduce utility bills. When selecting a two-stage furnace, Frigidaire suggests that consumers look for models that operate with an Annual Fuel Utilization Efficiency, or AFUE, of 80 percent or higher. The higher the AFUE rating is for a furnace, the lower your energy bills will be.