Picking out the correct 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 vital function in keeping its system working safely, efficiently and for a long time.

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

Ensuring your furnace uses a clean filter that is ideal for your needs is not only about keeping your furnace operating efficiently. It’s also about creating excellent indoor air quality for your residence.

Your health is important to the HVAC specialists at AC Sales. We've long been dedicated to improving indoor air quality in Lafayette. Here, we’ve answered frequent questions about HVAC filters, including that especially tricky question of what direction do you point a filter in your furnace or air conditioner?

When to Replace the Air Filter in Your Furnace

It's critical to replace dirty air filters in a furnace or air conditioner regularly. Dirty filters cause the system to worker harder than it should because it takes extra work to move air through the plugged-up filter.

Officials advise checking your furnace filter every 30 days and replacing it if it’s dirty. You’ll know if the filter needs to be changed because it will coated with dirt or dust. Homeowners who have dogs and cats will probably want to replace their furnace air filter more often, because a quality air filter will trap pet hair circulating in a home.

Where Is the Air Filter in My Furnace?

In general, a furnace air filter is normally installed in the return air duct or blower compartment before the return air reaches the furnace. This ensures air entering the system is filtered before it goes through the furnace components and is heated.

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

Is My Furnace Filter Just a Type of Air Filter?

The straightforward answer is, yes. In HVAC, a furnace filter and an air filter or air conditioning filter are effectively identical. While people may call them different things based on the current season— summer or winter—they are all filters that clean the air in your HVAC system.

They each remove dust, allergens, bacteria and other contaminants from the air that is drawn into the furnace and air conditioning system, making certain the air distributed throughout your home is clean and safe.

What Are MERV Ratings and What MERV Rating Do I Need?

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

MERV stands for Minimum Efficiency Reporting Values. The MERV rating measures the effectiveness of air filters at trapping airborne molecules. The rating scale ranges from 1 to 20, with bigger numbers indicating the power to filter small particles.

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

Which Way to Put the Air Filter in a Furnace or Air Conditioner

Installing an air filter in a furnace or air conditioner properly is crucial for the efficient operation of the unit. Air filters are supposed to face a particular direction, indicated by an arrow printed on the side of the filter frame. The filter should be installed with this arrow pointing in the direction of the furnace or AC, which is the direction of the airflow. If you're unsure about the airflow direction, remember that air always moves from the return duct to the heat or cooling source. Therefore, make sure the arrow points at the furnace or air conditioning unit.

Many people struggle with which direction to face their system's air filter. To help remember, consider taking a picture with your mobile 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 go. A handy time to inquire about this is during a routine furnace maintenance call.

How to Change a Furnace Air Filter

Changing the filter on your furnace or air conditioner is an easy process. Here is a step-by-step rundown of how to take out a dirty air filter and swap it for a new one:

  1. Turn off your furnace: Make a point to turn off your furnace before starting up the process.
  2. Find the furnace filter: Typically, the filter is located within the furnace or in the air return vent. Make a mental note or write down which direction the arrow points on the filter, because you’ll want the arrow on the replacement filter to point in the same direction.
  3. Remove the old filter: Be mindful not to knock out any dust or dirt.
  4. Document 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 another replacement.
  5. Insert new filter: Put in the new filter with the arrow pointing toward 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 securely and close any latches or clips that lock it in the compartment.
  7. Turn on your furnace: Once the clean filter is properly installed, you can turn your furnace back on.

Will a Dirty Air Filter Cause a Furnace Not to Work?

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