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How to Replace Your Furnace Filter 2019

January 17, 2019

How to Replace Your Furnace Filter 2019

When it it time to replace your furnace filter you want to make sure you have a good filter that is the correct size and the filter is going to protect your air quality as well as your HVAC equipment.

Watch Step by Step Replacing a Furnace Filter in the Video 

Furnace Filters are also know as air filters, HVAC filters, AC Filters, or Air Conditioner Filters. A dirty air filter can put a strain on your HVAC system causing long term damage to the equipment and increase your utility bills. You can then close the grill, close the latches and restart your system by pressing the mode button on your control until it is in the designed operation mode. In this case the system was put in to AUTO mode. 

 Turn Off Your AC or Heat by Changing the Mode to OFF

When replacing a filter behind a return grill vent, simply turn off your HVAC by turning off the unit from the control on the wall. This will turn off the motor and take the suction out of the system making it easy to remove the filter. Just press the mode button until it indicate off on the display. For some thermostats, you may just have an off switch.


Switch the Thermostat control to OFF using the mode button or off switch

 Notice in the image Auto is selected. By pressing the mode button the selection will move to the next operation. In the image above you would press mode once to move the selection to off.

How to Locate Your Furnace Filters

If you have asked where are my air filters located in my home? You are not  alone. Your air filter can be located in the blower compartment of your furnace, in an attached filter case or cabinet, or in a wall-mounted return air grille.

Air Filter Located Behind Return Grills

AC Filters are often located on the wall behind a return grill. If your filters are located in the return grill you may have multiple air filters to replace. Locate all of the return grills in the house. You may also have different size filters in each return. Don't assume they are all the same size. Check before ordering your filters.

Return Grill covering for furnace filter

 Sometimes you can see the filter behind the return grill. If the return grill has filters, it probably has a latch instead of screws. The latch can be on the top, side or bottom of the grill depending on how it was installed. The image below has a 2 latches on the bottom that swing out to unlock and open the grill.

Open Latch on Return Grill to replace Air Filter

Pull down on latches to open the grill and replace the AC filter. be careful when removing the grill that the whole grill doses not fall. It is a good idea to hold the grill securely when opening.

Find Your 1 inch Air Filters by Size

Open return grill to replace air filter

Once both latches are open the grill can open and the dirty filter can be replaced with a new air filter.

Reset the Filter

Most thermostat controls have a setting to reset the filter. This will create an alert or reminder on the control, usually at a set period such as, 3 months, when it is time to change your filter.

reset filter on thermostat control

On this control the filter reset is on the bottom left in the red box. Pressing the filter button resets the filter alarm so you will receive a warning on the display when it is time to change the filter. Setting a filter subscription is another good way to make sure you change your filters when it is time to properly maintain your system.


Furnace Filters located in a Cabinet or Case

Many furnaces have a compartment or a cabinet for a whole house air filter such as this Lennox furnace filter in it own cabinet. 

Filter Cabinet in Lennox furnace - Where is my furnace filter located

Now that you have located your filter.

Buy Your Replacement Filter Now

Find Your Filter Easily

Enter The Filter Part Number or Size from Your Current Filter in the Search, for example, enter X8795 or 20x20x1.





Related Links

Furnace Filters by Size

Carrier Air Purifier Cartridges

Lennox Furnace Filters

HEPA Filters and Air Cleaners



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Nominal vs Actual air filter size by Atomic


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Actual Filter Size- The Key to Making the Right Replacement Filter Purchase

The actual size as you might have guessed are the actual dimensions of the filter by length, width and thickness. This size is often on the filter right below the Nominal size and is usually labeled as the actual size. When you are buying a filter online the actual size is sometime in the product bullet point or the product description. If your filter does not have actual dimensions on the outside of the filter, you can measure you filter to get the correct dimensions. Some brands have a foam gasket on the outside of the filter, in this case, you will want to make sure you have a compatible actual size and that it also has the foam to ensure a snug fit. 

Lennox Air Filter X0851 with Foam strips

Examples of Nominal and Actual Sizes

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 Furnace filters should fit securely but should not have to be forced into position. If you have to force the filter into its slot, then it is probably too big. Forcing an improper filter size in a filter can cause it to buckle, damaging the filter or reducing its ability to function properly. Filters are a smaller than their slot to allow for easy replacement. Some HVAC units may need a filter with dimensions that are unique or uncommon. In these cases, a custom filter needs to be ordered.

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