Furnaces, Commercial Warm Air
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. The ASAP/ACEEE report, The Efficiency Boom, analyzed a standard level based on adopting the additional prescriptive requirements in ASHRAE 90.1, which require that units include an interrupted or intermittent ignition device (IID), have jacket losses not exceeding 0.75% of the input rating, and have either power venting or a flue damper. The average savings are around approximately 60 therms/year with an incremental cost of $300; this results in a 5.5 year payback. The estimated annual savings in 2035 are 7.7 trillion Btu and the net present value savings on products purchased through 2035 is $220 million.
Annual shipments are approximately 150,000.
Timeline reflects state standards from 2001 to present; federal standards from inception to present.