Which Way Does Furnace Filter Go?

The answer is here: The furnace filter should be installed with the arrow pointing toward the furnace. In simple words, the direction of flow should be the same as the airflow throughout your unit.

As a novice, altering or replacing an HVAC furnace filter at home can be daunting for homeowners. After all, there are two ways to install them: right and wrong. Many of you may not be aware of these methods. Therefore, learning how to install furnace filters in the right direction is important to ensure that the HVAC system operates at its best efficiency.

Installing filters in an inappropriate direction could adversely affect the furnace’s efficiency and performance while costing you money constantly. This information lets you know useful furnace filter tips, including the direction of the furnace filter, which is the right HVAC furnace filter, and other relevant information.

Therefore, learning how to install furnace filters in the right direction is important so that the HVAC system runs at its best efficiency.

By regular inspection, you can prevent air filters from getting clogged with dust, dirt, debris, and pet hairs. The best advice is to replace your HVAC filter at least every 3 months so that you and your family can continue to benefit from filtered air. This number could be lower depending on how many pets and occupants your property has. Therefore, the more often air filters are changed, the better energy efficiency and better indoor air quality you’ll get. To retain the efficiency of your HVAC, you’ll need to make sure the location for installation you choose is the right one.

Tips to find the right furnace filter/air handler direction

It’s worth remembering the simple saying, “Just go with the flow.” Make sure that the arrow on the filter points in the direction of air movement. Following this general rule ensures adequate filtration while maintaining uninterrupted airflow through your furnace unit.

Once the blower turns on, you should be able to put a few fingers, your hand, or even a piece of paper to determine where the filter moves.
Still unclear about what should be the air filter direction! Take a look at the below information. In the upcoming section, you’ll learn which direction the furnace filter runs in each type of HVAC system.

Furnace filter direction tips for different furnace types

Three types of furnaces are typically available in the Canadian market. Depending on the furnace type, the accurate location for the filter varies. But in most cases, the furnace filter is usually installed and positioned near the intake air blower fan to let air flows via the filter.

  1. Upflow furnace
  2. Downflow furnace
  3. Horizontal furnace

Upflow Furnace

An upright position is the most suitable location for most upflow furnaces. Placing them this way forces air from the bottom or side of the unit, then into the heat exchanger, and then it is forced upward into your building’s ductwork. Upflow furnaces are units placed in basements. In an up-flow furnace, the filter should be located in the blower chamber near the bottom of the unit, right next to the cold air return. With this furnace, the filter arrow should be placed facing upward.

Downflow furnace

With downflow furnaces, the air is taken in at the top, then heated inside, and then it’s taken out into your ductwork. Since it has downward-flowing air, make sure the filter is positioned at the top of the blower’s upper chamber. Downflow or attic furnace arrows should point down. In some downflow furnaces, a V-shaped filter system is installed, which requires two filters to be installed at the same angle in the chamber.

Horizontal furnace

In a horizontal furnace, air comes in from one direction, then extracts heat from it to cool it, and throws the air into a vent in the opposite direction. These furnaces usually come with a slide-in filter located on the side that draws cool air. The arrow point should be in the direction the wind is blowing.

How to install a furnace air filter in the right direction?

When you own the new furnace filter, look for the arrow directing the right airflow indication. It should be away from the return vent that draws the air that needs to be heated or cooled and toward the furnace. For better convenience, make a sign of the airflow direction arrow using a marker on the ductwork or furnace. It is advisable to involve the date when changing the filter to help in inspecting the duration between each alteration.

Safety tip: If the filter is placed inappropriately or in the wrong direction, the unit won’t adequately filter the air, causing damage to the HVAC unit. Also, it will reduce airflow via the furnace, making it to use more power and work harder.
Bottom line

Hopefully, you understand that the arrow pointing to the filter is always positioned in the direction that air flows through the unit. If you know that the arrow should point toward the furnace’s heating chamber, you don’t need to rethink which way the filter goes or which side to install the filter on.