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Single Versus Variable Speed

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Ask the expert: What’s the difference between Single and Variable Speed Systems?

Light switchIf your heating and cooling equipment is more than 20 years old, it probably came with a one-speed blower motor that cycles between ‘on’ and ‘off.’ These units have conventional split-capacitor electric motors that do not make speed adjustments.

single-speed air handler runs at full output all the time it’s on. It also draws maximum electricity and increases your utility bill. The ECM technology in a variable-speed unit allows the blower to run at slower, more energy-efficient speeds, saving as much as 40 percent on electricity costs.

Circulation diagramDuring the “off” cycle of a conventional one-speed furnace air handler, hot air in rooms rises to the ceiling and accumulates there. That is the reason that during the hot months of summer, we recommend that you run the fan for your furnace all the time as well as turn the ceiling fans on. A variable-speed blower can circulate air continuously at a lower volume with few “off” cycles. This prevents the stratification of hot air at the ceiling and keeps rooms more consistently comfortable.

Your heating and cooling system filter requires air circulation to do its job. During the intervals when a one-speed blower is off, airborne particulates are not drawn into the ductwork and filtered. Instead, they remain in the air, contaminating the air in living spaces. The continuous circulation provided by a variable-speed air handler keeps air moving through the filter at all times to maintain healthy room air quality.

Nathan on Kare 11

Nathan KareFor more tips on how to maintain your HVAC system, go to Heating and Cooling 101. Many homeowners have no clue about what it will take to replace their HVAC system. If you find yourself in that situation, read our blog post on HVAC replacement costs.

Ready for a no-obligation estimate on a new or replacement system?


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