Note:

Prior to October 9, 2024, any representations with respect to energy use or efficiency of furnace fans must be made either in accordance with the results of testing pursuant to this appendix or with the results of testing pursuant to this appendix as it appeared in the 10 CFR parts 200-499 edition revised as of January 1, 2023. On or after October 9, 2024, any representations, including certifications of compliance, made with respect to the energy use or efficiency of furnace fans must be made in accordance with the results of testing pursuant to this appendix.

0. Incorporation by Reference

DOE incorporated by reference in § 430.3, the entire standard for ASHRAE 37-2009 (RA 2019), as corrected by the ASHRAE 37-2009 Errata Sheet; ASHRAE 41.1-1986; as well as Chapter 1 of the 2021 ASHRAE Handbook and ASHRAE 103-2017. In cases where there is a conflict, the language of the test procedure in this appendix takes precedence over the incorporated standards.

1. Scope. This appendix covers the test requirements used to measure the energy consumption of fans used in weatherized and non-weatherized gas furnaces, oil furnaces, electric furnaces, and modular blowers. This appendix does not apply to furnace fans used in dual-fuel units.

2. Definitions. Definitions include the definitions as specified in section 3 of ASHRAE 103-2017 and the following additional definitions, some of which supersede definitions found in ASHRAE 103-2017:

2.1. Active mode means the condition in which the product in which the furnace fan is integrated is connected to a power source and circulating air through ductwork.

2.2. Airflow-control settings are programmed or wired control system configurations that control a fan to achieve discrete, differing ranges of airflow—often designated for performing a specific function (e.g., cooling, heating, or constant circulation)—without manual adjustment other than interaction with a user-operable control such as a thermostat that meets the manufacturer specifications for installed-use. For the purposes of this appendix, manufacturer specifications for installed-use shall be found in the product literature shipped with the unit.

2.3. Dual-fuel unit means a consumer product that includes both a heat pump and a burner in a single cabinet.

2.4. External static pressure (ESP) means the difference between static pressures measured in the outlet duct and return air opening (or return air duct when used for testing) of the product in which the furnace fan is integrated.

2.5. Furnace fan means an electrically-powered device used in a consumer product for the purpose of circulating air through ductwork.

2.6. Modular blower means a product which only uses single-phase electric current, and which:

(a) Is designed to be the principal air circulation source for the living space of a residence;

(b) Is not contained within the same cabinet as a furnace or central air conditioner; and

(c) Is designed to be paired with HVAC products that have a heat input rate of less than 225,000 Btu per hour and cooling capacity less than 65,000 Btu per hour.

2.7. Off mode means the condition in which the product in which the furnace fan is integrated either is not connected to the power source or is connected to the power source but not energized.

2.8. Seasonal off switch means a switch on the product in which the furnace fan is integrated that, when activated, results in a measurable change in energy consumption between the standby and off modes.

2.9. Specified airflow-control settings are the airflow-control settings specified for installed-use by the manufacturer. For the purposes of this appendix, manufacturer specifications for installed-use are those specifications provided for typical consumer installations in the product literature shipped with the product in which the furnace fan is installed. In instances where a manufacturer specifies multiple airflow-control settings for a given function to account for varying installation scenarios, the highest airflow-control setting specified for the given function shall be used for the procedures specified in this appendix, unless otherwise specified within this test procedure.

2.10. Standby mode means the condition in which the product in which the furnace fan is integrated is connected to the power source and energized, but the furnace fan is not circulating air.

2.11. Thermal stack damper means a type of stack damper that opens only during the direct conversion of thermal energy of the stack gases.

3. Classifications. Classifications are as specified in section 4 of ASHRAE 103-2017.

4. Requirements. Requirements are as specified in section 5 of ASHRAE 103-2017. In addition, Fan Energy Rating (FER) of furnace fans shall be determined using test data and estimated national average operating hours pursuant to section 10.1 of this appendix.

5. Instruments. Instruments must be as specified in section 6, not including section 6.2, of ASHRAE 103-2017; and as specified in sections 5.1 and 5.2 of this appendix.

5.1. Temperature. Temperature measuring instruments shall meet the provisions specified in section 5.1 of ASHRAE 37-2009 (RA 2019) (as corrected by the ASHRAE 37-2009 Errata Sheet), including the references to ASHRAE 41.1-1986, and shall be accurate to within 0.75 degrees Fahrenheit (within 0.4 degrees Celsius).

5.1.1. Outlet Air Temperature Thermocouple Grid. Outlet air temperature shall be measured as described in section 8.2.1.5.5 of ASHRAE 103-2017 and illustrated in Figure 2 of ASHRAE 103-2017. Thermocouples shall be placed downstream of pressure taps used for external static pressure measurement.

5.2. Humidity. Air humidity shall be measured with a relative humidity sensor that is accurate to within 5% relative humidity. Air humidity shall be measured as close as possible to the inlet of the product in which the furnace fan is installed.

6. Apparatus. The apparatus used in conjunction with the furnace during the testing shall be as specified in section 7 of ASHRAE 103-2017 except for section 7.1, the second paragraph of sections 7.2.2.2, 7.2.2.5, and 7.7, and as specified in sections 6.1, 6.2, 6.3, 6.4, 6.5, and 6.6 of this appendix.

6.1. General. The product in which the furnace fan is integrated shall be installed in the test room in accordance with the product manufacturer's written instructions that are shipped with the product unless required otherwise by a specific provision of this appendix. The apparatus described in this section is used in conjunction with the product in which the furnace fan is integrated. Each piece of the apparatus shall conform to material and construction specifications and the reference standard cited. Test rooms containing equipment shall have suitable facilities for providing the utilities necessary for performance of the test and be able to maintain conditions within the limits specified.

6.2. Downflow furnaces. Install the internal section of vent pipe the same size as the flue collar for connecting the flue collar to the top of the unit, if not supplied by the manufacturer. Do not insulate the internal vent pipe during steady-state test described in section 9.1 of ASHRAE 103-2017. Do not insulate the internal vent pipe before the cool-down and heat-up tests described in sections 9.5 and 9.6, respectively, of ASHRAE 103-2017. If the vent pipe is surrounded by a metal jacket, do not insulate the metal jacket. Install a 5-ft test stack of the same cross-sectional area or perimeter as the vent pipe above the top of the furnace. Tape or seal around the junction connecting the vent pipe and the 5-ft test stack. Insulate the 5-ft test stack with insulation having a minimum R-value of 7 and an outer layer of aluminum foil. (See Figure 3-E of ASHRAE 103-2017.)

6.3. Modular Blowers. A modular blower shall be equipped with the electric heat resistance kit that is likely to have the largest volume of retail sales with that particular basic model of modular blower.

6.4. Ducts and Plenums. Ducts and plenums shall be built to the geometrical specifications in section 7 of ASHRAE 103-2017 and section 6.7 of this appendix. An apparatus for measuring external static pressure shall be integrated in the plenum and test duct as specified in sections 6.4 of ASHRAE 37-2009 (RA 2019) (as corrected by the ASHRAE 37-2009 Errata Sheet), excluding specifications regarding the minimum length of the ducting and minimum distance between the external static pressure taps and product inlet and outlet, and section 6.5 of ASHRAE 37-2009 (RA 2019) (as corrected by the ASHRAE 37-2009 Errata Sheet). External static pressure measuring instruments shall be placed between the furnace openings and any restrictions or elbows in the test plenums or ducts. For all test configurations, external static pressure taps shall be placed 18 inches from the outlet.

6.4.1. For tests conducted using a return air duct. Additional external static pressure taps shall be placed 12 inches from the product inlet. Pressure shall be directly measured as a differential pressure as depicted in Figure 8 of ASHRAE 37-2009 (RA 2019) rather than determined by separately measuring inlet and outlet static pressure and subtracting the results.

6.4.2. For tests conducted without a return air duct. External static pressure shall be directly measured as the differential pressure between the outlet duct static pressure and the ambient static pressure as depicted in Figure 7a of ASHRAE 37-2009 (RA 2019).

6.5. Air Filters. Air filters shall be removed.

6.6. Electrical Measurement. Only electrical input power to the furnace fan (and electric resistance heat kit for electric furnaces and modular blowers) shall be measured for the purposes of this appendix. Electrical input power to the furnace fan and electric resistance heat kit shall be sub-metered separately. Electrical input power to all other electricity-consuming components of the product in which the furnace fan is integrated shall not be included in the electrical input power measurements used in the FER calculation. If the procedures of this appendix are being conducted at the same time as another test that requires metering of components other than the furnace fan and electric resistance heat kit, the electrical input power to the furnace fan and electric resistance heat kit shall be sub-metered separately from one another and separately from other electrical input power measurements.

7. Test Conditions. The testing conditions shall be as specified in section 8, not including sections 8.5.2 and 8.6.1.1 of ASHRAE 103-2017; and as specified in sections 7.1 and 7.2 of this appendix.

7.1 Ambient Temperature and Humidity Conditions. During the time required to perform all tests, maintain the room temperature within ±5 °F (2.8 °C) of the air temperature value measured at the end of the steady-state performance test (TRA). For condensing furnaces and boilers, maintain the relative humidity within ±5% of the relative humidity measured at the end of the steady-state performance test. During all tests, the room temperature shall not fall below 65 °F (18.3 °C) or exceed 85 °F (29.4 °C) and the relative humidity shall not fall below 20% or exceed 80%.

7.2. Measurement of Jacket Surface Temperature (optional). The jacket of the furnace or boiler shall be subdivided into 6-inch squares when practical, and otherwise into 36-square-inch regions comprising 4 in. x 9 in. or 3 in. x 12 in. sections, and the surface temperature at the center of each square or section shall be determined with a surface thermocouple. The 36-square-inch areas shall be recorded in groups where the temperature differential of the 36-square-inch area is less than 10 °F for temperature up to 100 °F above room temperature and less than 20 °F for temperature more than 100 °F above room temperature. For forced air central furnaces, the circulating air blower compartment is considered as part of the duct system and no surface temperature measurement of the blower compartment needs to be recorded for the purpose of this test. For downflow furnaces, measure all cabinet surface temperatures of the heat exchanger and combustion section, including the bottom around the outlet duct, and the burner door, using the 36 square-inch thermocouple grid. The cabinet surface temperatures around the blower section do not need to be measured (see Figure 3-E of ASHRAE 103-2017.)

8. Test Procedure. Testing and measurements shall be as specified in section 9 of ASHRAE 103-2017 except for sections 9.1.2.1, 9.3, 9.5.1.1, 9.5.1.2.1, 9.5.1.2.2, 9.5.2.1, and section 9.7.1; and as specified in sections 8.1 through 8.6 of this appendix.

8.1. Direct Measurement of Off-Cycle Losses Testing Method. [Reserved]

8.2. Measurement of Electrical Standby and Off Mode Power. [Reserved]

8.3. Steady-State Conditions for Hot Flow Tests for Gas and Oil Furnaces. Steady-state conditions are indicated by an external static pressure within the range shown in table 1 to this appendix and a temperature variation in three successive readings, taken 15 minutes apart, of not more than any of the following:

(a) 3 °F in the stack gas temperature for furnaces equipped with draft diverters;

(b) 5 °F in the stack gas temperature for furnaces equipped with either draft hoods, direct exhaust, or direct vent systems; and

(c) 1 °F in the flue gas temperature for condensing furnaces.

8.4. Steady-State Conditions for Hot Flow Tests for Electric Furnaces and Modular Blowers. Steady-state conditions are indicated by an external static pressure within the range shown in table 1 to this appendix and a temperature variation of not more than 5 °F in the outlet air temperature in four successive temperature readings taken 15 minutes apart.

8.5. Steady-State Conditions for Cold Flow Tests. For tests during which the burner or electric heating elements are turned off (i.e., cold flow tests), steady-state conditions are indicated by an external static pressure within the range shown in table 1 to this appendix and a variation in the difference between outlet temperature and ambient temperature of not more than 3 °F in three successive temperature readings taken 15 minutes apart.

8.6. Fan Energy Rating (FER) Test.

8.6.1. Initial FER test conditions and maximum airflow-control setting measurements. Measure the relative humidity (q) and dry bulb temperature (Tdb) of the test room.

8.6.1.1. Furnace fans for which the maximum airflow-control setting is not a specified heating airflow-control setting. The main burner or electric heating elements shall be turned off. Adjust the external static pressure to within the range shown in table 1 to this appendix. Maintain these settings until steady-state conditions are attained as specified in sections 8.3, 8.4, and 8.5 of this appendix. Measure furnace fan electrical input power (EMax), external static pressure (ESPMax), and outlet air temperature (TMax,Out). The measurement of EMax shall be taken over the final 30 seconds of the steady-state period, at intervals of no less than 1 per second, and averaged over the 30 second period.

8.6.1.2. Furnace fans for which the maximum airflow-control setting is a specified heating airflow-control setting. Adjust the main burner or electric heating element controls to the default heat setting designated for the maximum airflow-control setting. Burner adjustments shall be made as specified by section 8.4.1 of ASHRAE 103-2017. Adjust the furnace fan controls to the maximum airflow-control setting. Adjust the external static to within the range shown in table 1 to this appendix. Maintain these settings until steady-state conditions are attained as specified in sections 8.3, 8.4, and 8.5 of this appendix and the temperature rise (ΔTMax) is at least 18 °F. Measure furnace fan electrical input power (EMax), fuel or electric resistance heat kit input energy (QIN,H), external static pressure (ESPMax), steady-state efficiency for this setting (EffySS,Max) as specified in sections 11.2 and 11.3 of ASHRAE 103-2017, outlet air temperature (TMax,Out), and temperature rise (ΔTMax). The measurement of EMax shall be taken over the final 30 seconds of the steady-state period, at intervals of no less than 1 per second, and averaged over the 30 second period.

8.6.2. Constant circulation airflow-control setting measurements. The main burner or electric heating elements shall be turned off. The furnace fan controls shall be adjusted to the specified constant circulation airflow-control setting. If the manufacturer does not specify a constant circulation airflow-control setting in the installation and operations manual supplied with the unit, the lowest airflow-control setting shall be used. Maintain these settings until steady-state conditions are attained as specified in sections 8.3, 8.4, and 8.5 of this appendix. Measure furnace fan electrical input power (ECirc) and external static pressure (ESPCirc). The measurement of ECirc shall be taken over the final 30 seconds of the steady-state period, at intervals of no less than 1 per second, and averaged over the 30 second period.

8.6.3. Heating airflow-control setting measurements. For single-stage gas and oil furnaces, the burner shall be fired at the maximum heat input rate. For single-stage electric furnaces, the electric heating elements shall be energized at the maximum heat input rate. For multi-stage and modulating furnaces, the reduced heat input rate settings shall be used. Burner adjustments shall be made as specified by section 8.4.1 of ASHRAE 103-2017. After the burner is activated and adjusted or the electric heating elements are energized, the furnace fan controls shall be adjusted to operate the fan in the specified heating airflow-control setting that also allows for operation within the manufacturer-specified temperature rise range. In instances where a manufacturer specifies multiple airflow-control settings for a given function to account for varying installation scenarios, the highest airflow-control setting specified for the given function that also allows for operation within the manufacturer-specified temperature rise range shall be used. High heat and reduced heat shall be considered different functions for multi-stage heating units. Maintain these settings until steady-state conditions are attained as specified in sections 8.3, 8.4, and 8.5 of this appendix and the temperature rise (ΔTHeat) is at least 18 °F. Measure furnace fan electrical input power (EHeat), fuel or electric resistance heat kit input energy (QIN,k)external static pressure (ESPHeat), steady-state efficiency for this setting (EffySS) as specified in sections 11.2 and 11.3 of ASHRAE 103-2017, outlet air temperature (THeat, Out) and temperature rise (ΔTHeat). The measurement of EHeat shall be taken over the final 30 seconds of the steady-state period, at intervals of no less than 1 per second, and averaged over the 30 second period.

9. Nomenclature. Nomenclature shall include the nomenclature specified in section 10 of ASHRAE 103-2017 and the following additional variables:

60 = conversion factor from hours to minutes, (min/h) 0.24 = approximate specific heat capacity of dry air, (Btu/lb- °F) 0.44 = approximate specific heat capacity of saturated water vapor, (Btu/lb- °F) EffySS,i = Steady-State Efficiency in airflow-control setting i. For gas and oil furnaces EffySS,i is specified in sections 11.2.7 (Non-Condensing and Modulating), 11.3.7.3 (Condensing and Non-modulating), 11.4.8.8 (Non-Condensing and Non-modulating), or 11.5 (Condensing and Modulating) of ASHRAE 103-2017, in %. For electric furnaces or modular blowers, EffySS,i equals 100, in %. LJ = jacket loss as determined as specified in section 8.6 of ASHRAE 103-2017 or a default value of 1% if the jacket loss test is not performed, in % CCH = annual furnace fan constant-circulation hours ECirc = furnace fan electrical consumption at the specified constant-circulation airflow-control setting (or minimum airflow-control setting operating point if a default constant-circulation airflow-control setting is not specified), in watts EHeat = furnace fan electrical consumption in the specified heat airflow-control setting for single-stage heating products or the specified low-heat setting for multi-stage heating products, in watts EMax = furnace fan electrical consumption in the maximum airflow-control setting, in watts ESPi = external static pressure, in inches water column, at time of the electrical power measurement in airflow-control setting i, where i can be “Circ” to represent constant-circulation (or minimum airflow) mode, “Heat” to represent heating mode, or “Max” to represent cooling (or maximum airflow mode). FER = fan energy rating, in watts/1000 cfm HH = annual furnace fan heating operating hours HCR = heating capacity ratio (nameplate reduced heat input capacity divided by nameplate maximum input heat capacity) kref = physical descriptor characterizing the reference system Tdb = dry bulb temperature of the test room in, °F Ti,k,in = inlet air temperature at time of the electrical power measurement, in °F, in airflow-control setting i and heat setting k, where i can be “Circ” to represent constant-circulation (or minimum airflow) mode, “Heat” to represent heating mode, or “Max” to represent maximum airflow (typically designated for cooling) mode. If i = Heat, k can be “H” to represent high heat setting or “R” to represent the reduced heat setting. If i = Max or Circ, k is not needed. Ti,k,out = average outlet air temperature as measured by the outlet thermocouple grid at time of the electrical power measurement, in °F, in airflow-control setting i and heat setting k, where i can be “Circ” to represent constant-circulation (or minimum airflow) mode, “Heat” to represent heating mode, or “Max” to represent maximum airflow (typically designated for cooling) mode. If i = Heat, k can be “H” to represent high heat setting or “R” to represent the reduced heat setting. If i = Max or Circ, k is not needed. ΔTi,k = Ti,k,Out minus Ti,k,in, which is the air throughput temperature rise in setting i and heat setting k, in °F Qi,k = airflow in airflow-control setting i and heat setting k, in cubic feet per minute (CFM) MH = annual furnace fan maximum airflow hours QIN,k = nameplate fuel energy input rate, in Btu/h, at specified operating conditions k, based on the fuel's high heating value (“HHV”) determined as required in section 8.2.1.3 or 8.2.2.3 of ASHRAE 103-2017, where k can be “H” for the maximum heat setting or “R” for the reduced heat setting. W = humidity ratio in pounds water vapor per pounds dry air vair = specific volume of dry air at specified operating conditions per the 2021 ASHRAE Handbook, in ft 3/lb

10. Calculation of derived results from test measurements for a single unit. Calculations shall be as specified in section 11 of ASHRAE 103-2017, except for appendices B and C; and as specified in sections 10.1 through 10.10 and Figure 1 of this appendix.

10.1. Fan Energy Rating (FER)

Where: QMax = QHeat for products for which the maximum airflow-control setting is a specified heat setting, or

For products for which the maximum airflow control setting is only designated for cooling; and

The estimated national average operating hours presented in table 2 to this appendix shall be used to calculate FER.

Where: [89 FR 25801, Apr. 12, 2024]