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Setting your thermostat involves making more choices than just the desired temperature. You also have the option to set the system to either “fan on” or “auto.” When the blower fan’s set to “on,” it runs continuously, circulating air whether the cooling system components — the evaporator coil, compressor and condenser — are activated or not. In the “auto” setting, the blower fan runs only when the thermostat signals the evaporator coil and other components to cool the air.

setting your thermostatChoosing Between “On” and “Auto”

Some homeowners choose the “on” option instead of “auto” to simply sustain air circulation. Continuously moving air helps keep the indoor environment from stagnating, but there are more effective and efficient ways to move air than a 300-watt A/C blower fan. Energy-efficient ceiling fans, for example, use as little as 30 watts and provide a continuous flow of air circulation in rooms as well as increasing the sensation of coolness.

Why “On” Isn’t Always the Best Choice

Other downsides of setting the blower fan to “on” also include the following:

  • Because many central air conditioners are oversized, the cooling function tends to run short “on” cycles, turning off before humidity extraction at the evaporator coil has reached 100 percent. This leaves the coil surfaces wet with condensation. Continuing to operate the fan after the cooling components cycle off blows all that moisture back into the living spaces, making the house feel humid and more difficult to cool.
  • In addition, ductwork leaks pose potential air quality issues by pulling contaminated air from outside the system into the duct airflow. When the fan runs continuously in the “on” setting, the volume of tainted air infiltrating the airflow and circulated into your living spaces is greater, as is the potential for unhealthy indoor air quality.

For more information on setting your thermostat for optimum comfort, efficiency and air quality, check out Aqua Plumbing & Air’s air conditioning solutions or call (941) 306-3715.

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