Commercial warm air furnaces are defined as units with capacities of at least 225,000 Btu/hr (British Thermal Units per Hour). They are designed to supply heated air through a duct system. In practice, commercial furnaces are gas or propane heating sections of packaged roof-top units (RTUs) used for small- to mid-sized commercial buildings. RTUs are essentially air conditioners that may also contain a heating section.
Initial federal standards on commercial warm air furnaces were set under the Energy Policy Act of 1992. The legislation adopted standards originally set by the American Society of Heating, Refrigeration and Air-Conditioning Engineers in 1969 through their commercial building code called ASHRAE 90.1. These standards were modified by ASHRAE in 1999.
The current national standard, adopted in 2001, is equivalent to the thermal efficiency requirement in ASHRAE 90.1,but the code also contains additional prescriptive requirements for commercial warm air furnaces that are not included in the national standard.
In April 2015, DOE formed a working group to negotiate new energy conservation standards for commercial warm air furnaces. The working group recommendations were ultimately adopted by DOE in a December 2015 direct final rule. Standards go into effect January 1, 2023.
Annual shipments are approximately 150,000.