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January 28, 2023

Is It Ok for My Furnace to Run Constantly?

Reasons For A Furnace Running Constantly - LG Home Comfort

A furnace that has been running all the time should not be ignored. It’s because a constantly running furnace may signal a system malfunction. This blog post will cover why you shouldn’t allow this, the possible reasons, and what you should do if a furnace runs constantly.

Is It Bad for My Furnace to Run Constantly?

A furnace that’s running non-stop is not necessarily bad. During the coldest days in winter, it is normal for a furnace to run almost constantly to keep the home warm. As long as the furnace is running efficiently and not making strange noises, the constant operation is likely nothing to worry about.

But in general, your furnace should not constantly be running. Otherwise, it could indicate a problem with your heating system. In this case, have a qualified HVAC (Heat, Ventilation, and Air Conditioning) technician inspect your system and address issues that make it run constantly. This way, you can save time, money, and stress.

What Do Running And Cycles of a Furnace Mean?

When it comes to operating a furnace, understanding the concept of “running” and “cycling” can help you gain control over your home’s temperature. The term “running” means how long the furnace needs to operate to reach its desired temperature, while “cycling” refers to the on/off pattern it follows.

For example, if your thermostat’s setting is 65°F, your furnace will switch on and start running a cycle until that temperature is reached. But once it reaches that point, the furnace shuts off, which usually leads to a drop in temperature. As soon as this happens, your furnace will turn on again as part of another cycle until it can restore the set temperature levels.

What Is the Average Cycle of a Furnace?

The average cycle is an essential element to consider in maintaining a well-functioning furnace to keep your home comfortable during cold winter.

During regular operation, it will turn on for about 10 to 15 minutes and then turn off again, repeating this pattern twice every hour. However, if the temperatures outside are freezing or you are hosting a large gathering in your home and need more heat, your furnace may increase its cycles to 3 to 10.

What Are the Reasons for a Furnace Running Constantly?

When the temperatures aren’t so cold, and your furnace has been running non-stop, it can indicate a problem with the system. These include:

The Air Filter is Dirty 

The most common reason why a furnace run continuously is because of a dirty furnace filter. Dirty air filters restrict airflow and force your unit to work harder to heat your house. Be sure to check your air filter every month and replace it when necessary.

The Furnace Fan Is Set to “On”

Another possible reason your furnace is running without stopping is that the fan setting on your thermostat might be set to “on.” This will cause your fan to run continuously, regardless of whether or not the heat is needed. To fix this issue, switch the fan setting from “on” to “auto” on your thermostat.

The Temperature Is Set Too High

If you have a programmable thermostat, another potential reason why your furnace could be running constantly is that the temperature might be set too high. Try lowering the temperature slightly and see if that helps reduce the time your furnace runs each day.

The Furnace Might Not Be Derated Properly 

If all other potential issues have been ruled out, it could also mean that something is wrong with how your furnace was derated during installation. Your HVAC contractor should have derated (or sized) your system correctly when they installed it. Otherwise, it could result in an overworked system and constant running times for your furnace.

What to Do if Your Furnace Runs All the Time?

When your furnace runs without stopping, it is essential to identify and fix the problem as soon as possible. If your furnace runs constantly, here are some tips:

Tip #1: Check the Thermostat Setting

When troubleshooting furnace problems, check the thermostat settings first. Ensure you set the temperature correctly and that they reflect the desired temperature you want your home to maintain. If they are incorrect, adjust them to match what you want.

Tip #2: Inspect the Air Filter

Clean air filters allow your furnace to work efficiently and allow the hot air to circulate throughout your home. Filters that are dirty and clogged reduce airflow, so your furnace works harder and more frequently to supply your rooms with heated air.

Tip #3: Look into Weatherizing

Weatherization protects your home from the elements by making it more energy efficient. This can be done by sealing windows, doors, and other openings to help prevent heat loss from outside sources. This reduces energy costs by keeping warm air inside while helping minimize how much work your furnace has to do to maintain a comfortable temperature inside.

Additionally, consider insulation upgrades, particularly if your house is old.

Tip #4: Check Your Ductwork

Checking for leaks or breaks in your ductwork is also a good idea. These issues can cause heated air from within the ducts to escape into unheated areas of your house, like attics or crawl spaces, causing more strain on your system as it compensates for lost warmth.

Tip #5: Check the Vents

Make sure that all vents in each room of your house are open and free of obstructions, such as furniture or rugs, so that air can flow freely through them without obstruction. This will allow for efficient heating throughout each room of your home rather than just having heat concentrated in one area due to blocked vents elsewhere in the house.

Tip #6: Check the Thermostat Itself

Inspect the thermostat itself for any corroded wires or dirt buildup that may prevent it from functioning correctly. Also, double-check that it has nothing wrong with the thermostat by replacing its batteries or ensuring it is properly connected if you have a smart thermostat.

Tip #7: Have Your Heating System Checked by an HVAC Technician

If none of the above techniques work, call an HVAC technician who can inspect your system thoroughly and diagnose any underlying issues causing your furnace to run too long each day. They can identify and address potential problems, so your unit will start running optimally again.


No homeowner wants their furnace to run constantly. Unfortunately, sometimes these problems arise regardless of how diligent you are about maintenance tasks like changing filters regularly. If you notice that your furnace starts experiencing this problem, solve it as soon as possible by following the tips mentioned above. Ultimately, it’s best to call an experienced HVAC technician who will assess and fix your furnace’s issues.

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