The "On" and "Auto" settings on an air conditioner (AC) thermostat refer to different fan operation modes.
"On" Setting: When the thermostat is set to "On," the fan of the air conditioner will run continuously, even when the cooling or heating system is not actively cooling or heating the air. In this mode, the fan circulates air throughout the space regardless of whether the AC is actively cooling or heating. It can help maintain a constant airflow and provide better air circulation in the room. However, running the fan continuously can consume more energy and may result in slightly higher energy bills.
"Auto" Setting: When the thermostat is set to "Auto," the fan operates only when the cooling or heating system is actively cooling or heating the air. In this mode, the fan turns on automatically along with the AC unit or furnace, and it shuts off when the desired temperature is reached. Once the cooling or heating cycle is complete, the fan stops running until the next cycle starts. The "Auto" mode tends to be more energy-efficient since the fan operates only when needed.
Choosing between the "On" and "Auto" settings depends on your preferences and the specific requirements of your indoor environment. Here are some factors to consider:
Comfort: The "On" setting can provide more consistent airflow and help with air filtration, which may be beneficial for individuals with allergies or for maintaining a more even temperature throughout the space. However, some people find the constant fan noise bothersome. The "Auto" setting can be quieter when the fan is not running.
Energy Efficiency: The "Auto" setting is generally more energy-efficient since the fan runs only during active cooling or heating cycles. This can result in lower energy consumption and reduced utility costs compared to the "On" setting, which runs the fan continuously.
Air Quality: If you have concerns about indoor air quality, running the fan continuously ("On" setting) can help circulate and filter the air, potentially reducing the concentration of airborne pollutants. However, it's important to maintain clean filters and ensure the system is properly maintained to prevent the accumulation of dust or contaminants.
Ultimately, choosing between the "On" and "Auto" settings depends on your personal comfort preferences, energy considerations, and the specific requirements of your indoor space.