How to Change Your Furnace or AC Filter – ACE HI PLUMBING, HEATING, & AIR

Maintaining a clean furnace filter not only helps to keep your furnace’s interior components clean and in good operating order, but also contributes to improved air quality by reducing the amount of allergens and harmful particles in the air. All furnaces are equipped with an air filtration system designed to trap pollutants, dirt, and dust. Service technicians may replace your furnace filter during an annual inspection, but these filters are constantly working to keep the airborne pollutants out of the air you breathe and away from the operating parts of your furnace. With all of these debris piling on each and every day, frequently changing or cleaning your filter is essential to maintaining the unit’s optimal operating efficiency. This is also essential to keeping your monthly bill low. It is important to understand how to replace your filter and how often is often enough.


First, it is important to understand how filters operate and why it is so important to your HVAC system. The furnace operates through a cold and hot air return process. The process starts in the cold air vents and cold air travels through the furnace filter to start the heating process. As cold air moves through the system, hot air return begins at the furnace, travels through the heat exchanger, and then out through the vents into the home. The warm air, replaces the cooler air and the cold air is pushed back through the return vent to begin the process all over again. As the air continues to pass through the system, dust and dirt particles in the air are trapped by the filter preventing it from building up on the interior components of the unit and slowing down the operation. When the filter doesn’t get changed regularly, it becomes more difficult for the air to pass through the returns, meaning your furnace is performing overtime to keep air moving.


Air filters should be changed or cleaned every few months, before they get full. It depends on the manufacturer’s directions whether that should take place every month or every three months. Be sure to read all directions supplied with your new filter carefully. Also, you should frequently check to see if your filter should need a replacement as necessary. For example, if you have pets or if you smoke, you may find your filter turning black with pollutants sooner that you may have expected.

The location of the filter varies depending on the furnace’s make, model, and manufacturer. They generally are found near the fan motor, which is kept in the blower chamber. Filters also may be kept near the systems ductwork. Some could be exposed and easily located from the exterior of the unit, or other furnaces are manufactured with the filter inside the fan enclosure. These units require removal of an access panel to uncover the filter. Homeowners should consult their owners manual for factory instructions on how to change their individual unit’s filter.


Filters come in a variety of types, including fiberglass, HEPA, polyester, pleated, and electrostatic filters. Each has different capabilities and performance based on the size, density of the material and amount and size of particles it’s designed to filter. Filters are available in reusable or disposable options. Reusable filters require replacement every few years, but depending on the level of pollutants captured, they should be cleaned with water or a vacuum on a monthly basis. Disposable filters require a homeowner to purchase a new filter every few months, but eliminate the potential for exposure to contaminants during the cleaning process. This type of filter is regarded as more efficient at trapping smaller debris. Although reusable filters may seem more environmentally friendly, they are generally less effective at trapping small dust particles and this may reduce the overall efficiency of the unit. Regardless, all air filters are most effective when new and clean.

Once you determine the type of filter you want, it’s important to ensure you purchase the correct size. Looking at the old filter being replaced is the simplest way to determine the size of the new filter. Typically, the size is printed on the filter frame and is presented with the dimensions measuring width by height by depth. If the size is not on the frame of the filter, it can be found be measuring the dimensions with a tape measure or reading your furnace’s owner’s manual.


Both brand name and generic filters can be used in heating and cooling units. Generic filters may cost less, but often have the same specifications as brand name filters. Buying a filter in the right size will have a greater impact on performance than the brand. Installing the wrong size could allow air to bypass the filter and leak through to the blower fan, causing slow air flow, excessive dirt build-up, and a soiled blower fan. More costly repairs, cleaning, and service depends on the severity of the build-up. If you are concerned about purchasing the wrong furnace filter, don’t hesitate to talk to your maintenance technician about their recommendations for keeping your unit running in top shape year round.

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