What are three common forced air furnace configurations?

Three common forced air furnace configurations include the upflow, downflow, and horizontal systems. Upflow furnaces direct heated air upward into the ductwork, typically installed in basements. Downflow furnaces push air downward, often used in homes with ductwork in ceilings or attics. Horizontal furnaces are designed to be placed in attics or crawl spaces, directing air through ducts parallel to the floor.