I have heard it is most efficient to run the fan constantly for a central air-conditioning unit. Is that correct?
Central-air unit located in the Midwest; high temps and humidity.
Yes. Running the fan allows for the continuous flow of air and allows for mixing of the cooler air with the warm. This creates a balance throughout the home, reducing the amount of energy used by the AC unit.
It also helps control moisture and keeps air from getting musty in certain areas of the house.
The energy savings from reducing the AC workload are much higher than the energy lost from the continual running of the fan.
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