Picking out the proper furnace filter and changing it when it gets dirty is as important to your HVAC system as changing the oil is to your car. Each plays a critical part in keeping its system working safely, efficiently and for a long time.

A clogged furnace filter loses its effectiveness, permitting potentially harmful particles to move through your home. It also restricts airflow, which can damage your furnace and shorten its life span.

Making sure your furnace uses a clean filter that is ideal for your needs is not merely about keeping your furnace working efficiently. It’s also about delivering good indoor air quality for your household.

The quality of the air your family breathes is important to the HVAC specialists at Phelps Heating & Cooling, Inc.. We've long been dedicated to enhancing indoor air quality in Hodgenville. Here, we’ve answered common questions about HVAC filters, including that particularly tricky question of what direction do you point a filter in your furnace or air conditioner?

When Should I Replace My Furnace Air Filter?

It's critical to replace dirty air filters in a furnace or air conditioner periodically. Dirty filters cause the system to worker harder than it should because it takes more energy to force air through the plugged-up filter.

Officials advise checking your furnace filter every month and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will be gray or black from dirt or dust. Homeowners who have pets will very likely have to replace their furnace air filter more often, because a quality air filter will trap pet hair circulating in a home.

Locating Your Furnace's Air Filter

In general, a furnace air filter is commonly located in the return air duct or blower compartment before the return air gets to the furnace. This ensures air being pulled into the system is filtered before it moves through the furnace components and is heated.

Depending on the furnace model, the filter may be positioned on the right, left, bottom or in some cases, inside the furnace. It's generally housed within a slot, frame or cabinet for simple access and replacement. Always refer to your furnace's owner manual for important information concerning filter location of your furnace.

Are Air Filters and Furnace Filters the Same Thing?

The simple answer is, yes. In HVAC, a furnace filter and an air filter or air conditioner filter are effectively the same. While people may call them different things based on the current season— warm or chilly months—they are all filters that clean the air in your home.

They each eliminate dust, allergens, bacteria and other airborne debris from the air that is drawn into the furnace and air conditioning system, making certain the air flowing through your home is clean and safe.

What Is the MERV Rating System and What MERV Rating Do I Need?

Once you locate your old furnace filter and decide when it should be substituted for a clean one, it’s time to select a replacement. That means picking the level of filtration that you need. One method to do this is by choosing an appropriate MERV rating for your needs.

MERV is an abbreviation for Minimum Efficiency Reporting Values. The MERV rating indicates the effectiveness of air filters at trapping airborne particles. The rating scale ranges from 1 to 20, with higher numbers indicating enhanced capabilities to filter smaller particles.

Experts say a filter with a MERV rating between 8 and 13 offers an ideal balance between having healthy indoor air quality without needlessly restricting airflow. However, people with some health conditions might need to use a filter with a higher MERV rating.

How to Place the Air Filter in a Furnace or AC Unit

Putting an air filter in a furnace or air conditioner correctly is necessary for the efficient operation of the unit. Air filters are supposed to face a specific direction, indicated by an arrow printed on the side of the filter frame. The filter should be installed with this arrow pointing at the furnace or AC, which is the direction of the airflow. If you're not sure about the airflow direction, try to remember that air always moves from the return duct towards the heat or cooling source. Therefore, be sure that the arrow points toward the furnace or air conditioning unit.

Many people are confused by which direction to point their system's air filter. To help remember, consider snapping a quick photo with your cell phone after the filter has been correctly installed by a professional. Or, you also could ask a technician to use a marker to write on the outside of your furnace which direction the filter should point. A perfect time to inquire about this is during a routine furnace maintenance visit.

How to Change a Furnace Air Filter

Replacing the filter on your furnace or AC is an easy process. Here is a step-by-step rundown of how to retreive a dirty air filter and replace it with a new one:

  1. Turn off your furnace: Make sure to turn off your furnace before starting up the process.
  2. Find the furnace filter: Typically, the filter is found within the furnace or in the air return vent. Take note of which direction the arrow points on the filter, because you’ll want the arrow on the new filter to point the same way.
  3. Slide out the old filter: Be mindful not to knock out any dust or dirt.
  4. Note the date: Write down the date you changed filters on the new filter's frame. This will help you keep track of when it's time for the next change.
  5. Insert new filter: Put in the new filter with the arrow pointing in the direction of the furnace, which is the direction of airflow and should be the same direction the arrow pointed on the dirty filter you just removed.
  6. Secure the filter: Make sure the new filter fits nicely and close any latches or clips that lock it in the compartment.
  7. Turn on your furnace: Once the replacement filter is completely installed, you can turn your furnace back on.

Will a Dirty Air Filter Cause Problems for a Furnace?

The short answer is, yes, a dirty air filter can cause a furnace to quit working or reduce its lifespan. Changing your furnace or air conditioning filter is one of the simplest things you can do to keep your system operating efficiently.