Propeller fan unit heaters and centrifugal fan unit heaters are designed for use in space heating applications. The units are typically used in areas with high ceilings, and are exposed in the space to be heated. Unit heaters offer low installed cost, and are able to heat large volume areas without requiring extensive duct systems.
Duct furnaces are designed for use in ducted applications with a separate air handling device such as a horizontal blower assembly. By utilizing a separate air source, greater application flexibility in airflow delivery can be obtained. Multiple duct furnaces can be used with an air handling unit to provide zone heating.