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

Keeping your Furnace safe when away

Heating with a mid or high efficiency propane or natural gas furnace? If you plan on leaving your home or cottage for an extended period of time during the heating season, you should only reduce your thermostat to 16 degrees C (60 F) to prevent damage from the following:

  1. Return air temperatures are too low, and condensation will form on the primary heat exchanger. This causes corrosion and leads to premature failure
  2. Outside air temperature can cause freezing of the condensation after the secondary heat exchanger. This causes cracking and can lead to water leaks damaging the electronic control board of your furnace.

To prevent expense repairs, leave your thermostat set to 16 C (60 F) or higher. If your furnace fails completely due to freeze-up, the results could be a frozen dwelling with split pipes leading to tremendous water damage.