This question actually involves two different settings that people often confuse, the system mode and the fan mode. For system mode, which is Heat, Cool, Auto, Off, or Emergency Heat, Auto mode is useful in spring and fall when you need both heating and cooling in the same day. In Auto, the thermostat will automatically switch between heating and cooling to maintain your desired temperature range. In summer, most experts recommend setting system mode to Cool only, and in winter to Heat only, to prevent the system from accidentally switching. For fan mode, which is Auto versus On, you should almost always leave the fan set to Auto. In Auto fan mode, the blower fan only runs when the system is actively heating or cooling, which saves energy and helps with humidity control. If you set the fan to On, the blower will run continuously 24 hours a day even when not heating or cooling, which increases your electricity bill, can make the house feel more humid in summer because moisture from the coil re-evaporates, and wears out the fan motor faster. The On setting is only useful if you have severe air filtration needs or want to circulate air constantly for a short period.
1 votes
Marked as accepted