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Should I Run My Furnace Fan Continuously?

Some homeowners may wonder if they should run their furnace fans continuously, and it’s certainly a question that a lot of professional HVAC technicians hear. Some ask about the advantages and disadvantages of leaving the furnace fan in the On position. Others assume that a continuously running furnace fan signifies that something is faulty with the unit. The truth is, whether you should or should not run the furnace fan continuously depends on several factors.

First, What Is a Furnace Fan?

The fan is sometimes also referred to as a furnace blower, and it is the part of the furnace system that pushes and circulates warm air into the various areas of your home. These days, the vast majority of central heating systems are forced-air systems, and as the name suggests, they need access to air in order to function properly. They pull air in from an outside source, filter it, heat it, and then distribute the heated air throughout the home through the air ducts. A furnace fan is the easiest way for a system to pull in the air needed for the system to run.

In general, furnace fans are equipped with a motor that has a single horsepower or less. The actual size of the motor will depend on the model and size of the furnace. Alternatively, there are some instances when the size of the motor is actually relative to the amount of space that the furnace is aiming to heat, including the number of vents located throughout the house. Most furnace fan models are capable of about 1,200 revolutions per minute (RPMs), yet some revolve at a slower rate. When looking at a residential home, the maximum speed that would be appropriate is generally about 1,500 RPM.

Why Is the Furnace Fan Running Continuously?

Close up of furnace fan.

This has to do with how you’ve set the thermostat in your home. What setting is it on? Do you consistently have the air conditioning on? Or the heat? Most types of thermostats have three settings: Auto, On, and Off. If you’ve set your thermostat to a comfortable 69 or 70 degrees and have it On, the furnace fan will continually be running. If you switch the setting to Auto, it will only engage when the temperature drops below the set temperature.

This is all relative and assumes that the furnace fan has been well-maintained and working properly. A furnace fan that won’t stop spinning can also signify a problem. There can be a defect in the fan’s switch, for instance, and it might require a manual override. If you think there might be a defect in the way your furnace fan is operating, it’s best to call a professional HVAC technician to come out and investigate the issue.

Benefits of Continuously Running the Furnace’s Fan

There are a handful of reasons why you might consider running your furnace continuously, and they include better circulation of the heating or cooling, lower utility bills, and improved air quality.

Better circulation of heated or cooled air means that your system isn’t having to shut down and then start up again in a fractured back-and-forth cycle. This also contributes to a decreased energy bill, as you’re having a more consistent flow of heated or cooled air. In terms of air quality, when you’re running the furnace continuously, the air is pulled in and processed through the filter. If you have a highly efficient filter and UV light, the filtering is additionally cleaning the indoor air. This means there will be less dust, fewer particulates, and other microscopic particles circulating about the house and landing on your carpets or furniture.

Better air quality can make all the difference for someone with breathing issues, so having the furnace fan running throughout the day and night can keep the air fresh, clear, and breathable for all who reside in the house. Good quality air is important for all, even those who don’t have any respiratory health concerns and can keep you and your loved ones healthier throughout the winter season. Lastly, running the furnace fan can also contribute to a decreased level of humidity during the cold winter, by running the air through the evaporator, ultimately pulling more moisture out of the air over time.

When Should You Stop Running the Fan Continuously?

Homes built after 2015 are required to have all air ducts sealed and secured, which means that air doesn’t escape through any leaky ducts. If your home was built before 2015, it makes a lot of sense to have a professional come out to do a test and see how airtight your air ducts are. Up to 45 percent of the average utility bill can be due to leaky ductwork. It is very important to make sure that your system is running efficiently and that you’re not wasting any energy—or money.

Another time of the year when you’ll want to review how often your fan is running is during the peak of summer. This is especially true if you have air ducts in the attic. Temperatures can reach over 130 degrees in attics on the hottest days of the summer. Running your furnace fan nonstop would waste both energy and money in this case.

Entek is your local, knowledgeable, and professional HVAC one-stop shop. We have an array of air conditioning and heating as well as central HVAC systems, thermostats, and ducts to upgrade and update your system. Our technicians are skilled and trained for installations and repairs and have the know-how to help with any of your HVAC unit concerns. Call us today and let us help revitalize your system so it’s in its most efficient and environmentally friendly state.


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