If you install the filter in the wrong direction, air will struggle to flow through the filter material and your air handler will have to work overtime to compensate for the loss of airflow. Not only is this a waste of energy, but it can also damage the air conditioner or heating system. The direction of the HVAC filter is important because air flows through it in one direction. While both sides look the same, one is more porous to allow air to enter.
Otherwise, air cannot pass through and the unit itself must work harder and harder, leading to higher energy consumption and loss of efficiency. The air filter can accumulate a lot of dust, so it is important to always turn off the boiler power. Alternatively, you can note the direction of the arrows in the old filter before changing it and make sure that the new one also looks in that direction. If you install the air cleaner incorrectly, the oven will have to work a lot harder to do its job properly.
Therefore, they should face the ceiling if the filter is placed on the ceiling; and they must face the wall if it is somewhere on the wall. If air flows through the filter before entering the HVAC system, the arrow will point toward the blower. Regardless of the HVAC system you have, each unit needs a properly tuned quality filter to keep indoor air quality clean and your unit operating at peak efficiency. Air filters can become clogged with dust, mold, or pet dander, and as a result, air cannot easily pass through them.
The pleated part of the filter should face you when you install it and the other side, which usually consists of a metal mesh or cardboard frame, should point towards the return. Both sides of the air cleaner look the same, but that doesn't mean you can use them interchangeably. That arrow should always face the furnace and away from the return duct that carries the air that needs to be heated or cooled. HVAC air filters come in different sizes; they can be 12 to 24 inches (30.48 to 60.96 cm) wide and 12 to 36 inches (30.48 to 91.44 cm) long.
Look for the airflow arrows printed on the side of the air cleaner that indicate in which direction the filter should be inserted. All air filters have specific performance ratings, indicating how well they can remove large and small particles from the air.