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How to replace an air filter

Whether you call it an AC filter or a furnace filter, it means the same thing. Air filters are a critical yet often overlooked part of a central HVAC system. To keep your home’s air filter in tip-top shape, it’s important to have it checked, maintained and changed regularly. It’s simple, but it can still feel like a chore when you have to locate where a filter is, remove an old one and insert a new one.

Why replacing an air filter is important

  • Damage prevention for your HVAC system.  A dirty air filter is the No, 1 reason for HVAC system failure because it restricts airflow into your HVAC system’s air handler. This restricted airflow places additional strain on the air handler fan motor and could, over time, burn out the motor and cause your system to overheat and eventually fail. If you keep up to date on checking your air filter’s condition, you can prevent such failure and extend the life of your AC unit.
  • Cleaner air. Changing your home’s air filter ensures cleaner, fresher and healthier air. A fresh filter means your HVAC system is not constantly circulating dust, pollen and other small particles in the air. Instead, your system will be able to purify the air, leaving it clean and healthy so you can breathe easy and avoid aggravating allergies.
  • Cost savings.  A dirty air filter uses much more energy than a new, clean air filter, which means a much higher electricity bill for you. By keeping your air filter clean and in good condition through regular maintenance, you could potentially save up to 15% on utility costs.
  • Less energy consumed. As mentioned above, an air filter that is clogged means a harder-working HVAC system, which translates to large amounts of carbon monoxide and other greenhouse gases being released. Something as simple as changing an air filter regularly can go a long way toward making a difference.

How often should I change my air filter?

Air filters quickly become clogged with debris, especially during the cooling season when air conditioners are running around the clock. As a general rule, you’ll want to replace pleated air filters and furnace filters in your home every 90 days. At a bare minimum, you’ll want to change your filters every spring and fall if you have AC and hot-air heat (change immediately if someone in the home has had a cold, flu or other communicable illness). Tip: Write the date on the filter.

Changing the filter

In most cases, the filter is located next to the air handler of your HVAC system. The air handler is a large metal box containing the fan and fan motor. It can be to the side or above it. Sometimes the air filter is located in a return vent. Many times, the vent nearest to your thermostat is where it can be found.

Once you’ve found it, determine that you have the correct size with which to replace it. (If you have the product manual for your HVAC unit, check there first.) Look for the numbers printed on the filter. If there are no dimensions or they are faded, you can measure it yourself with a measuring tape. These are written as length x width x depth (for example: 18x20x1). Lay the filter flat on the ground and start by measuring top-to-bottom for length, left-to-right for width, and front-to-back for depth. You should have three numbers written in inches. With those dimensions, you’ll know what size to buy (anyone at the DIY or home improvement store can help).

If your filter is in the return vent, take these steps after you’ve located it:

  1. Loosen the fasteners holding the front of the grille to the vent and gently remove the cover. Set it aside. The air filter should be located directly behind the cover.
  2. Simply reach in and pull out the old filter and grab your new filter.
  3. Identify the arrow pattern on the edge of the filter. The direction of the arrows is important to ensure proper airflow. The arrows should not point out or at you. If they do, airflow will be restricted.
  4. Once you find the arrows, position them so that they are facing the wall.
  5. Place the air filter back into the return duct opening, gently easing the bottom portion of the filter in first and then the top.
  6. Double-check that the arrows are pointing toward the duct.
  7. Make sure it’s fitting snugly into the opening.
  8. Put the cover back on.
  9. Tighten the fasteners.

If your filter is next to the air handler unit, follow these steps (they’re very similar):

  1. Turn off the power: It’s important that you switch off the power at the unit itself and also at the circuit breaker.
  2. Remove the old filter: Simply slide it out of the slot that holds it in place.
  3. Check the condition: Once you’ve taken out the AC filter, check its condition. Does it look clogged with dirt and dust? If you hold it up to the light, you probably can’t see much light coming through. This filter needs to be replaced or cleaned, depending on the type of filter you are using. Even if it’s been in use less than the time recommended by the manufacturer, replace it anyway.
  4. Insert the new filter: Now you just need to put it back in the right way. An arrow on the filter’s frame shows you the direction that air should flow through the filter, which is always away from the return air duct and toward the air handler mechanism. When you insert the filter back in the housing, make sure that arrow points away from the return and toward the air handler.

When your air filters need changed, keep in mind that they can be loaded with germs and dust mites. Filters should be bagged on the spot.

Time and cost to replace an air filter

An air filter can cost anywhere from $1 to $50 depending on the type. A professional will charge for a service call, which is typically one hour’s time plus a trip charge (if any).

It will take a few minutes to an hour to change it — longer if it’s located in a less accessible space such as an attic or a crawl space.

What if there are still problems with the filter or installation?

If there are issues with replacing the filter, a few common reasons might be forgetting to remove the plastic wrapper or installing it backward (it must be installed with arrows pointed in the same direction as the airflow). It could be the wrong size, or the wrong MERV rating. A MERV rating stands for Minimum Efficiency Reporting Values, and it reports a filter’s ability to capture larger particles. This value is helpful in comparing the performance of various filters (the higher the MERV rating, the better).  Sometimes, the cardboard frame could even be bent or damaged during installation, so double-check that.

Get a remote diagnosis with Anew

If an AC filter malfunctions after installing a new AC filter, it might be symptomatic of a more serious issue, and you might want to consider a professional option. Anew offers an easy, efficient and affordable repair service with remote diagnosis for only $20.

Get a remote diagnosis

Video chat with an expert to pinpoint your home’s issues, then get them repaired fast.

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Get a remote diagnosis

Video chat with an expert to pinpoint your home’s issues, then get them repaired fast.

Start My Repair

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