Understanding the Basics of a Variable-Speed Furnace

Understanding the Basics of a Variable-Speed Furnace

Understanding the Basics of a Variable-Speed FurnaceA variable-speed furnace offers more comfort, increased energy savings and greater longevity than a single-stage heating system. The term “variable speed” refers to the motor inside the air handler that powers the fan. These types of motors embed the most advanced motor technology available in residential HVAC systems.

Variable-speed motors are actually electronically-commutated motors (ECMs), and use electricity differently than the more common permanent split capacitor (PSC) motor used in HVAC systems. ECMs use inverters to change the power from alternating current (AC) to direct current (DC), a fundamental improvement in power usage. They also contain circuitry that adjusts their running speed based on the amount of heating or cooling a home needs.

Their use of DC and adjustable running speeds increase their energy efficiency measurably, though it won’t change the furnace’s energy efficiency rating because of how the U.S. Department of Energy (DOE) evaluates furnace efficiency. The DOE rates furnaces based on how much of the fuel they use goes toward heating the home directly instead of being wasted as combustion gases. However, forced-air furnaces rely on blower motors to distribute the air, and will lower electric bills.

Besides reduced electrical consumption, a variable-speed furnace provides these benefits.

  • Greater indoor comfort. The fan adjusts its running speed to the amount of heat your home needs. It will run more slowly than a PSC, which distributes the heat more evenly throughout your home, especially in rooms further from the air handler.
  • Quiet operation. ECM motors ramp up quietly as they start and stop their cycles, reducing blower noise.
  • Better indoor air quality. Because the motor runs more slowly, it pulls more air through the air handler’s filter, resulting in better filtration of your air. The motor also senses when the filter is excessively dirty, and compensates for the reduced airflow, preventing harm to your system.
  • Increased durability. ECMs last longer than PSC motors because they avoid frequent starts and stops in their running cycles.

To learn more about a variable-speed furnace, contact Powers Heating & Cooling, serving homeowners in the Peachtree City area since 2001.

Our goal is to help educate our customers in Peachtree City, Georgia and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about variable-speed furnaces and other HVAC topics, download our free Home Comfort Guide or call us at 770-487-2040.

Credit/Copyright Attribution: “iQoncept/Shutterstock”

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