When you’re setting your thermostat, you have the choice to run the fan in the HVAC system. You can have it constantly running by choosing the “on” setting, or running it only during the heating or cooling cycle with the “auto” setting. Both choices have advantages and disadvantages, depending on the circumstances.
Using the “On” Setting
Setting your thermostat to the “on” position will keep the air circulating through your home constantly. This has the following advantages:
- Improved indoor air quality since the air is constantly moving through the filter
- More even distribution of heated or cooled air after the HVAC system shuts off
- Less wear on the fan from constant cycling
The “on” setting also has some major drawbacks, including:
- Dramatically increased energy usage, as the fan can consume over 300 watts of power when running
- More frequent air filter changes due to constant filtration
- Increased humidity in the summer due to the constant airflow evaporating the remaining water from the evaporator coils between cycles
- Faulty ducts may leak more because of the increased airflow
If you have family members who suffer from allergies or asthma, the better filtration available with the “on” setting may be the best choice. In most cases, however, the increased energy usage outweighs the benefits.
Using the “Auto” Setting
In this mode, the fan will only run when the HVAC system requires it to distribute conditioned air. The benefits of using the “auto” setting include:
- Less energy usage since the fan stops between cycles
- The air filter lasts longer since it experiences fewer cycles
- Better dehumidification
The “auto” setting also has the following disadvantages:
- Less air filtration since the fan stops between cycles
- Possible hot or cold spots between cycles
- More wear on the fan from starting and stopping often
For most households, this is the best option, unless you have a variable-speed fan that can reduce airflow between cycles or a thermostat with a timed circulation mode.
For more information about setting your thermostat correctly, talk to our HVAC specialists at Ace Hardware Home Services, Inc. We’ve served the Dayton and Springfield areas for three generations.
Our goal is to help educate our customers in Dayton, Ohio about energy and home comfort issues (specific to HVAC systems).
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