What is the name of the furnace configuration where return air enters from the top and supply air leaves at the bottom?

The configuration of a furnace where return air enters from the top and supply air leaves at the bottom is known as a downflow furnace. This design utilizes gravity to enhance the circulation of air. In downflow systems, return air is drawn in from above, typically through ceiling-level ducts or grilles, and then heated air is delivered back to the living spaces from the bottom, ensuring that warm air rises naturally due to convection.

Downflow furnaces are particularly effective in certain applications, such as in basements or spaces where the furnace is situated above the areas needing heating. This setup allows for efficient distribution of warm air throughout the space, enhancing comfort and system efficiency. The design also eases installation and ductwork requirements in particular building layouts.

In contrast, upflow furnaces have return air entering from the bottom and supply air exiting from the top, while horizontal furnaces are installed horizontally and can operate with return and supply air on either side. Ventilated furnaces refer more broadly to any furnace designed with ventilation as a primary feature, without specifying a directional airflow. Understanding these configurations helps in selecting the appropriate furnace for specific heating needs based on space and air distribution preferences.