HVAC filter arrow which way

Which Way Does a Furnace Air Filter Go? Airflow Direction Diagram

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Which Way Does a Furnace Air Filter Go? Airflow Direction Diagram illustrating a home HVAC system. Blue arrows show air flowing from the return air duct, through the air filter, and into the furnace air handler. A yellow callout emphasizes that the printed arrow on the filter's frame must point in the same direction as the airflow, pointing towards the furnace.

A backwards furnace filter fits, and that is precisely the problem. It slides into the slot, the system runs, and nothing sounds obviously wrong until the utility bill climbs or the blower starts working harder than it should. We’ve pulled incorrectly installed filters from ceiling returns, attic air handlers, and vertical closet furnaces. The furnace … Read more