Over time, the dust particles from the air build up on the furnace filter. The filter eventually needs to be replaced because it becomes ineffective. If your furnace’s filter hasn’t been replaced in some time or looks dirty, here’s how to change a furnace filter.
- Check your furnace’s filter size
- Select the right MERV rated filter
- Change the furnace filter
Check Your Furnace’s Filter Size
First, you’ll need to know what size filter your furnace takes. The easiest way to do this is to remove the filter in your furnace and see what size it is. The size should be stated on the side of the filter somewhere. Assuming the filter is the correct size for your furnace, this is the size you should look for.
You can also check what size filter your furnace takes by looking in the owner’s manual.
Select the Right MERV Rated Filter
Second, you’ll need to determine what quality filter you want. Furnace filters are rated on a minimum efficiency reporting value (MERV) scale. The scale runs from 1 to 16, although residential furnace filters typically fall between 4 and 12. The higher a filter’s rating is, the more particles it removes from the air.
You don’t necessarily want the highest-rated filter you can find, though. Not only do higher-rated filters tend to cost more than lower-rated ones, but you might not need the additional filtering ability, In fact, a filter rated too high could slow the airflow through your furnace too much and decrease your furnace’s efficiency.
To determine what rating you need, first check the manufacturer’s specified airflow for your furnace. Make sure no filter you choose will decrease the airflow below the manufacturer’s specified rate, for doing so will adversely affect your furnace’s efficiency and its blower’s life span.
Once you know what filters are compatible with your furnace, you may want to consider the following:
- MERV 4 filters are usually inexpensive and filter out large airborne particles, including pollen
- MERV 7 to 8 filters provide a good balance between filtering ability, airflow, and price; they catch mold and pet dander
- MERV 11 and 12 filters are high-efficiency filters that may be necessary if anyone in your family has severe allergies or a compromised immune system
FPR Rated Filters
If you buy your furnace filters at The Home Depot, you may find it marked with an FPR rating instead of a MERV rating. The Home Depot developed the FPR rating and it closely resembles the MERV system.
- FPR 4 to 5 filters are “Good.” They catch large airborne particles including dust, pollen, and pet dander.
- FPR 6 to 7 filters are “Better.” They also catch mold, and bacteria.
- FPR 8 to 9 filters are “Best.” They also catch microscopic allergens, and most smoke.
- FPR 10 and above filters are “Premium.” They also catch odors and smog particles.
Buy the lowest rated filter that meets your needs. Higher rated filters make your furnace work harder and use more energy, which may not be necessary in your home.
Change the Furnace Filter
Once you’ve purchased a filter, you’re ready to change it. Take out the old filter. Notice which way the arrows on the filter are pointing so you can install the new one the same direction. Slide the new one in place, being sure the arrows on the filter are pointing in the direction that air flows through the filter. Close the filter door (if you have one), and you’ve successfully changed your furnace filter.
By staying on top of furnace filter changes, you can make sure the filter doesn’t become too dirty and compromise your furnace.
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