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Proposed Revisions of Part of the Test Procedures for Furnaces and Boilers in ASHRAE Standard 103-1993



S T. Liu


The U.S. Department of Energy's (DOE) procedure for testing the Annual Fuel Utilization Efficiency (AFUE) of residential central furnaces and boilers references ASHRAE Standard 103-1993. The standard has been used by the furnace/boiler industry to obtain the AFUE values of their products as required by DOE. ASHRAE Standard Project Committee (SPC) 103R is in the process of making revisions to the standard to address some shortcomings and to improve the calculation procedure on the basis of comments and experiences from the industry. This report presents proposed revisions to certain part of the test procedure to address some of the comments. The proposed revisions include a new procedure to calculate the average burner on/off times of modulating furnaces/boilers during the cyclic operation of the burner, a revised method for the calculation of the annual burner operating hours, and an extension of the procedure to calculate the off-period flue loss of oil-fired equipment designed with a long post purge time. This report also provides the background information on the derivation of the integral functions listed in Appendix E of ASHRAE Standard 103-1993 that have not been formally documented. Those integral functions were used for producing the graphs in the standard for the hand calculation of the off-period losses with a calculator, and also in the numerical algorithm in the computerized calculation procedure.
NIST Interagency/Internal Report (NISTIR) - 6913
Report Number


Annual energy consumption, Annual Fuel Utilization Efficiency, ASHRAE standard 103, burner operating hours, DOE test procedure, integral functions for off-period losses, step-modulating furnaces/boilers, two-stage furnaces/boilers


Liu, S. (2002), Proposed Revisions of Part of the Test Procedures for Furnaces and Boilers in ASHRAE Standard 103-1993, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed May 20, 2024)


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Created September 1, 2002, Updated February 19, 2017