When Should I Change My Air Conditioner's Air Filter at Home?

February 26, 2015

Sometimes we’re asked what is the number one thing that Gaithersburg area homeowner's can do to ensure efficient functionality of their air conditioning and heating system between their regular tune-ups? The answer is simple this; remember to change the heating and air conditioning air filter. Changing furnace and return air filters is extremely important to the ideal operation of your HVAC system, as well as your home's air quality. Did you know indoor air pollution is one of the top five environmental health risks? You probably don’t consider it as you sit and watch TV, but this is the air you breathe day and night. Changing the air filters is not a tough thing to do for most Gaithersburg homeowners, but there are often two obstacles to actually completing this job:

  1. Understanding just how often to replace your furnace or air conditioner filter.
  2. Remembering to change air filters when needed.

When To Change Your Air Filters

Most filters have a timeline printed on the box or plastic. It may instruct "Lasts up to 3 months" or "Change filter every 90 days". Pay attention at the store and you'll notice that some are meant to only last a month, while other manufacturers (like Honeywell) have created media air cleaners with filters meant to be changed once every 6-12 months. The norm seems to be once every 3 months for most higher quality filters, but we have a rule of thumb that we recommend our customers to go by. If they're dirty, change them! A dirty air filter can exacerbate or cause damage to pricey equipment, like your compressor, so it's better to change it out more often than not. If you want to stick to the manufacturer's recommended limit, we suggest marking the date on the filter when you swap it out, and programming a reminder for yourself in your phone or on a calendar. Also be aware that your filter manufacturer sometimes has a different recommendation from your HVAC system manufacturer.

Determining how often to change your air filters relies upon several factors:

  • Which air filter your system requires
  • The entire air quality of your Gaithersburg area home
  • Pets – Dogs, cats, etc.
  • Number of occupants in the house
  • General air pollution in the Gaithersburg area or construction taking place nearby

For your standard 1"-3" air filters, the manufacturer specs basically say to change them bi-monthly, which is really a great rule of thumb. Still, general rules aren't always for everybody. If you put up with light to moderate allergies, you may need to upgrade the air filter or change them even more regularly than OEM specifications. On the other hand, if you're in a remote area, own a less occupied home (like a vacation home) or an area where there are fewer cars around, replacing your air filters each year may be quite sufficient. Why do pets matter so much? They have a tendency to shed, which can clog your air filter quick. Obviously, the air filter is just doing its job by trapping pet hair and dander, but exceptionally dirty filters can cause diminished HVAC performance.

In summary:

  • Seldom used home or single occupant homes without pets or allergies: Change 6-12 months
  • Common suburban home without pets: Change every 90 days
  • Add a dog or cat: Change every 60 days
  • More than one pet or have allergies: Change every 30-45 days

How To Remember To Change Your Air Conditioner's Air Filters

Here’s an easy way to stay on top of this; sign up for the Service Experts Email Club. When you do, you can elect to receive (or not) great email coupons and newsletters with a lot of tips and discounts on AC repairs and tune-ups. But wait… there’s more, your email subscription preferences let’s you set a reminder to change your Gaithersburg area home's air filter every 30, 60, 90, 120 or 365 days, or any date you find most convenient.

How to replace your return air filter

Most of you know how to replace the air filter in their unit, but some houses have an extra filter in the return ductwork. Whether you have one or not is dependent on which HVAC system you have. Your unit is made to handle a maximum amount of pressure in your home sweet home, and the more filters you have the fiercer the blower motor works, which can shorten the life expectancy of your system if it isn't designed for it. Learning whether you have a return filter and replacing it is easy:

  1. Find your return air vents.
  2. Some covers have screws and some have tabs. Unscrew or pull tabs to remove from the wall.
  3. Check for a filter. If one is there, pull it out and write down the size.
  4. Verify the filter type is the one recommended by the manufacturer.
  5. If filter is dirty, replace with the manufacturer's recommended filter of the same size and type.
Crazy as it may seem, filters can greatly alter your home's airflow, which is why we recommend referring to the manufacturer. A higher quality HEPA filter that is designed to catch tinier dust will obstruct airflow more than a cheaper filter. With restricted airflow comes greater pressure on your system, so you should verify that your HVAC system was built to handle it. Otherwise, you may experience reduced heating and cooling efficiency in your home, and system parts may wear out much faster than otherwise.
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