Furnace Fan Operation

Furnace Fan Running Continuously (ON setting) vs during heating/cooling cycle (AUTO setting)

Pros to running continuously (ON setting at thermostat)

  • circulates the air within the dwelling constantly, this creates more temperature uniformity throughout the house and reduces hot spots / cold spots
  • cleaner air within the dwelling as the constant circulation forces more air through the filtration system and UV light system (if equipped)
  • possible extended life span of fan, the frequent starts and stops on auto cause startup stress to the motor

Cons to running continuously (ON setting at thermostat)

  • Furnace air filter will clog up quicker, requiring change out of filter more often
  • Electricity costs will increase, the fan motor could draw upwards of 500 watts
  • Ducts that run through attics, unconditioned crawl spaces, or close to exterior walls can pick up heat during summer months and cause your air conditioner to run more often to counteract this heat gain
  • House may feel colder in winter as you feel the air flow when the burner is off. The airflow from the ducts will be the same temperature as the ambient room temperature air, but will feel cooler