How to Change Your Furnace Filter

 

How To Change You Furnace Filter

Is it time to change your furnace filter?  Probably.  To keep your furnace working optimally, the filter should be changed periodically.  Standard 1" filters should be changed about every three months. Wider 4" and 5" filters can last up to a year.  But if you have pets, allergies, have done home remodeling, you may need to change the filter more often.

What happens if you don't change your filter when its needed?

The furnace may not operate properly to heat or cool your home.  Do you want a service call because your filter was not changed?  A dirty filter will also cost you money since the furnace is not working efficiently.  If that's not bad enough, your furnace could actually be damaged if your filter is clogged.

With all that could go wrong having a dirty furnace filter, this easy maintenance project is well worth the little effort and low cost.

Tool & Supplies

 TOOLS 

None!  How many home improvement projects with such a big impact can be done with absolutely no tools?

 SUPPLIES 

New air filter. (see  STEP 1  ).

Steps To Change Your Furnace Filter

t &Padding

 STEP 1  Determine Filter Size

Of course, you'll need a new filter.  If you already know the filter size, you can skip to the next step.  If not, here's what to do.  First, you'll need to locate the furnace filter.  One edge of the filter should be visible and accessible when you are standing in front of the furnace.  Each furnace is a little different so I provided some examples here (filter is highlighted with yellow box):

Filter Location - Example 1

Filter Location - Example 2

Filter Location - Example 3

Okay, now that you've found the filter, you can check its size.  The good news is that the filter size is printed on one or more sides of the filter.  If you're lucky, you'll be able to see the size marking on the filter without doing anything and you can just write it down.  The size should be something like "16 x 25 x 1" which is the overall dimensions of the filter. Once you have the size, you can move onto  STEP 2 .

But it the filter size is not visible, you'll have to remove the old filter to check its size.  So follow   STEP 4  through  STEP 7   below but just replace the old filter (in the same orientation) for now.  Once that's done, you're ready to move onto  STEP 2 .

 STEP 2  Buy a New Filter

The new filter should of course be the same size as the old filter.  That's the easy part.  But when you go to buy a new filter, you'll find many varieties available at a wide range of prices.  Which is the right filter for you?

You should select a filter that meets your specific needs.  For example, there are filters that claim to help in reduction of allergens, odors, bacteria & viruses, pollutants, etc. so you might opt for one that targets one or more of those conditions.  But there is another thing to check before you buy a filter.

Ratings:

Furnace filters have a rating that specify the performance of the filter.  If you want to learn more about these ratings, you can check out this guide:

MERV vs. MPR vs. FPR    The Definitive Guide

Which filter should you select?  That's up to you depending on your filtering needs, budget, and filter availability.  A good choice is the 3M Filtrete filter which provides very good performance at a mid-range price:

Example of a Very Good 16" x 25" x 1" Furnace Filter

Before you place your filter order or pick it up at the store, make sure you double-check the filter size!

 STEP 3  Determine Direction of Air Flow

At this point, you're ready to install the new filter but before you do, you must determine the airflow direction of your furnace.  Skipping the step could could cause improper operation and possible failure of the filter.

Most furnace filters are designed to work with the air passing through them in a particular direction.  A furnace system collects the "stale" air from your house from return vents and passes it through the filter before heating (winter) or cooling (summer) the air for redistribution throughout the house.  The airflow within the furnace is always in the direction of the collected returned air into the furnace for heating or cooling.

To determine the airflow direction, look at your furnace and you should see duct-work that leads into the main body of the furnace.  Since stale air travels from the return vents into the furnace, this is the direction of the air flow.  Here's a couple example furnaces and the direction of the airflow indicated.

Air Flow Right to Left Example

Air Flow Left to Right Example

You might not have a furnace with side-to-side airflow.  Below is an example of a furnace that collects stale air from the room directly and passes into the furnace from front to back for re-conditioning.

Air Flow Front to Back Example

Tip: Once you've determined the direction of the furnace airflow, you just might want to mark it on your furnace with a permanent marker for future reference.

 STEP 4  Turn Furnace Off

In order to remove and replace the furnace filter, you'll want to make sure your furnace doesn't turn on while you are replacing the filter.  There are two ways to do this.

Some furnaces have an ON/OFF switch installed so the furnace can be turned off during maintenance.  Here's an example of one:

If you have a furnace ON/OFF switch, go ahead and switch it to the OFF position now.  If you don't have an ON/OFF switch, no problem.  Just adjust your thermostat by about 5-10 degrees to keep the furnace off for awhile. If its winter and the heat is on, reduce the thermostat setting.  If it's the summer and the central A/C is on, increase the thermostat setting.

 STEP 5  Remove Old Filter

Grab the filter by its frame and gently pull out.  The filter should slide out with little resistance.  Don't pull too hard, the filter can get hung-up and you don't want to risk leaving part of the filter behind in the furnace.  If the filter seems stuck, try wiggling it back and forth or up and down to free it up.

When you are removing the filter, check for any airflow direction marks on the filter and see if they match your expectation.  Was the filter installed correctly?

 STEP 6  Install New Filter

Before you install the new filter, make sure to remove any plastic or packing material that might be covering the filter!  Find the airflow direction mark on the new filter and flip the filter in the correct orientation.  Slide the filter in the furnace slot making sure the filter is fully seated all the way in.

 STEP 7  Turn Furnace Back On

If you have a furnace ON/OFF switch, turn it back ON.  If you adjusted your thermostat to keep your furnace off, go ahead and readjust it to your desired setting.  Done!

Tip: Need help remembering when to change your filter?  Try setting a reoccurring reminder on your smartphone.