The direction of the HVAC filter is of utmost importance since air passes through it in one direction. Although both sides may look the same, one is more porous to allow air to enter. If the filter is not installed correctly, the unit must work harder and harder, leading to higher energy consumption and a decrease in efficiency.
Air filtershave arrows printed on them that indicate how they should be installed.
These arrows should point in the direction of the air flow through the system, which is away from the supply ducts and (usually) towards the blower. If the filter is in the ceiling, the arrow should face up. If it is on a wall, it should point towards it. Fortunately, most air filters are designed in such a way that they won't fit properly if they are not inserted correctly.
Look for the airflow arrows printed on the side of the air cleaner that show which way it should be inserted. This is illustrated in the image below. The side of the filter that has a wireframe should face outwards, away from the unit. With an upflow oven, the filter will be located near the bottom of the unit in the blower compartment next to the cold air return.
To determine which filter is right for you, find out what size you need (this can be found in your current air filter or in your oven or air conditioner's owner's manual), compare MERV ratings and cost, and consider any special needs your home may have. When you install an air cleaner incorrectly, you won't be able to filter your home's air efficiently, which can lead to a variety of maintenance issues. If you remember that the arrow should always point towards the oven heating compartment, you won't have to worry about which way to install the filter or which side of it goes up or down. My problem stems from the fact that my last batch of filters don't have airflow arrow indicators or a wire mesh; they are multi-stage with a removable fiberglass (velcro) layer, an activated carbon honeycomb layer, and finally a pleated paper layer with a very thin fiberglass layer attached.
This allows for effective trapping of particles in the air while minimizing any decrease in airflow through the system. But regardless of what type of furnace you have, the filter will always be located near the intake air blower fan and positioned so that air flows through it. Fiberglass filters should be changed every 1 to 2 months and pleated paper filters should be changed every 3 to 5 months. If you install your filter in reverse, air will struggle to pass through it and your air handler will have to work overtime to make up for this loss of airflow.
There are three basic types of ovens and each one has its own location for its filter. The arrows on your filter should point towards your oven so that they indicate which way air flows through your ducts and into your oven. This will help you remember which direction your filter should go when you replace it in a few months' time. Forced-air ovens recirculate air throughout your home, blowing out cooled or heated air while drawing spent air for another cycle.