HVAC systems are designed to blow out hot or cold air and extract spent air, recirculating it throughout the house. If the filter is on the wall, the arrow should be facing the wall. Most filters have an arrow printed on them, usually in one of the corners. If you don't have an arrow, you'll want the side with the wire frame to face outward.
This means that the side with the wire frame will be on the outside, closest to you, and the side without it will be inside closer to the unit. For any air filter, whether for an air conditioner or an oven, the arrows always point in the direction of air flow. When installing a new air filter in the AC return duct, the arrows should face inward, indicating the direction in which air flows. The return duct in your home is pulling air. Here is a size guide for AC air filters to use when you need to find the right size air filter for your home. When you place the air filter in the wrong direction, it cannot capture dust and air particles, and they will remain floating in the air.
This is because a dirty and clogged air filter will significantly impair the efficiency of the boiler and air conditioner. When you insert the air filter incorrectly, you cannot filter the air in your home efficiently, which can lead to a variety of maintenance issues. Some downflow furnaces have a V-shaped filter system and need two filters placed in the compartment at a V-shaped angle. It is important to always disconnect the boiler power when changing an air filter as it can collect a lot of dust. With an upflow oven, the filter will be located near the bottom of the unit in the fan compartment next to the cold air return.
For any type of heating and air conditioning system, the arrows should always point in the direction of airflow. An HVAC air filter is manufactured so that one side has a filter material and the other side has material to reinforce it. These filters need to be changed regularly to remain efficient, as dust and other air particles accumulate in them and reduce airflow.