10 CFR Appendix N to Subpart B of Part 430 - Appendix N to Subpart B of Part 430—Uniform Test Method for Measuring the Energy Consumption of Consumer Furnaces Other Than Boilers
DOE incorporated by reference in § 430.3, the entire standards for ASTM D2156R13 and IEC 62301. DOE also incorporated selected provisions of ASHRAE 103–1993.
1. Scope. The scope of this appendix is as specified in section 2 of ASHRAE 103–1993 as it pertains to furnaces other than low pressure steam or hot water boilers or to electric boilers. Low pressure steam or hot water boilers and electric boilers are addressed in appendix EE of this subpart.
2. Definitions. Definitions include those specified in section 3 of ASHRAE 103–1993 and the following additional and modified definitions.
Active mode means the condition in which the furnace is connected to the power source, and at least one of the burner, electric resistance elements, or any electrical auxiliaries such as blowers, are activated.
Control means a device used to regulate the operation of a piece of equipment and the supply of fuel, electricity, air, or water.
Draft inducer means a fan incorporated in the furnace that either draws or forces air into the combustion chamber.
Gas valve means an automatic or semi-automatic device consisting essentially of a valve and operator that controls the gas supply to the burner(s) during normal operation of an appliance. The operator may be actuated by application of gas pressure on a flexible diaphragm, by electrical means, by mechanical means or by other means.
Installation and operation (I&O) manual means instructions for installing, commissioning, and operating the furnace, which are supplied with the product when shipped by the manufacturer.
Isolated combustion system means a system where a unit is installed within the structure, but isolated from the heated space. A portion of the jacket heat from the unit is lost, and air for ventilation, combustion and draft control comes from outside the heated space.
Multi-position furnace means a furnace that can be installed in more than one airflow configuration (i.e., upflow or horizontal; downflow or horizontal; upflow or downflow; and upflow, or downflow, or horizontal).
Off mode means a mode in which the furnace is connected to a mains power source and is not providing any active mode or standby mode function, and where the mode may persist for an indefinite time. The existence of an off switch in off position (a disconnected circuit) is included within the classification of off mode.
Off switch means the switch on the furnace that, when activated, results in a measurable change in energy consumption between the standby and off modes.
Oil control valve means an automatically or manually operated device consisting of an oil valve for controlling the fuel supply to a burner to regulate burner input.
Standby mode means any mode in which the furnace is connected to a mains power source and offers one or more of the following space heating functions that may persist:
(a) Activation of other modes (including activation or deactivation of active mode) by remote switch (including thermostat or remote control), internal or external sensors, and/or timer; and
(b) Continuous functions, including information or status displays or sensor-based functions.
Thermal stack damper means a type of stack damper that relies exclusively upon the changes in temperature in the stack gases to open or close the damper.
3. Classifications. Classifications are as specified in section 4 of ASHRAE 103–1993 for furnaces.
4. Requirements. Requirements are as specified in section 5 of ASHRAE 103–1993 for furnaces.
5. Instruments. Instruments must be as specified in section 6 of ASHRAE 103–1993.
6. Apparatus. The apparatus used in conjunction with the furnace during the testing must be as specified in section 7 of ASHRAE 103–1993 (except for the excluded sub-sections as enumerated at § 430.3(g)(15)); and as specified in sections 6.1 through 6.5 of this appendix.
(a) Install the furnace in the test room in accordance with the I&O manual, as defined in section 2.6 of this appendix, except that if provisions within this appendix are specified, then the provisions herein drafted and prescribed by DOE govern. If the I&O manual and any additional provisions of this appendix are not sufficient for testing a furnace, the manufacturer must request a waiver from the test procedure pursuant to § 430.27.
(b) If the I&O manual indicates the unit should not be installed with a return duct, then the return (inlet) duct specified in section 7.2.1 of ASHRAE 103–1993 is not required.
(c) Test multi-position furnaces in the least efficient configuration. Testing of multi-position furnaces in other configurations is permitted if energy use or efficiency is represented pursuant to the requirements in 10 CFR part 429.
(d) The apparatuses described in section 6 of this appendix are used in conjunction with the furnace during testing. Each piece of apparatus shall conform to material and construction specifications listed in this appendix and in ASHRAE 103–1993, and the reference standards cited in this appendix and in ASHRAE 103–1993.
(e) Test rooms containing equipment must have suitable facilities for providing the utilities (including but not limited to environmental controls, applicable measurement equipment, and any other technology or tools) necessary for performance of the test and must be able to maintain conditions within the limits specified in section 6 of this appendix.
6.2 Forced-air central furnaces (direct vent and direct exhaust).
(a) Units not equipped with a draft hood or draft diverter must be provided with the minimum-length vent configuration recommended in the I&O manual or a 5-ft flue pipe if there is no recommendation provided in the I&O manual (see Figure 4 of ASHRAE 103–1993). For a direct exhaust system, insulate the minimum-length vent configuration or the 5-ft flue pipe with insulation having an R-value not less than 7 and an outer layer of aluminum foil. For a direct vent system, see section 7.5 of ASHRAE 103–1993 for insulation requirements.
(b) For units with power burners, cover the flue collection box with insulation having an R-value of not less than 7 and an outer layer of aluminum foil before the cool-down and heat-up tests described in sections 9.5 and 9.6 of ASHRAE 103–1993, respectively. However, do not apply the insulation for the jacket loss test (if conducted) described in section 8.6 of ASHRAE 103–1993 or the steady-state test described in section 9.1 of ASHRAE 103–1993.
(c) For power-vented units, insulate the shroud surrounding the blower impeller with insulation having an R-value of not less than 7 and an outer layer of aluminum foil before the cool-down and heat-up tests described in sections 9.5 and 9.6, respectively, of ASHRAE 103–1993. However, do not apply the insulation for the jacket loss test (if conducted) described in section 8.6 of ASHRAE 103–1993 or the steady-state test described in section 9.1 of ASHRAE 103–1993. Do not insulate the blower motor or block the airflow openings that facilitate the cooling of the combustion blower motor or bearings.
6.3 Downflow furnaces. Install an 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. However, do not insulate the internal vent pipe during the jacket loss test (if conducted) described in section 8.6 of ASHRAE 103–1993 or the steady-state test described in section 9.1 of ASHRAE 103–1993. 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 103–1993. 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 an R-value not less than 7 and an outer layer of aluminum foil. (See Figure 3–E of ASHRAE 103–1993.)
6.4 Units with draft hoods or draft diverters. Install the stack damper in accordance with the I&O manual. Install 5 feet of stack above the damper.
(a) For units with an integral draft diverter, cover the 5-ft stack with insulation having an R-value of not less than 7 and an outer layer of aluminum foil.
(b) For units with draft hoods, insulate the flue pipe between the outlet of the furnace and the draft hood with insulation having an R-value of not less than 7 and an outer layer of aluminum foil.
(c) For units with integral draft diverters that are mounted in an exposed position (not inside the overall unit cabinet), cover the diverter boxes (excluding any openings through which draft relief air flows) before the beginning of any test (including jacket loss test) with insulation having an R-value of not less than 7 and an outer layer of aluminum foil.
(d) For units equipped with integral draft diverters that are enclosed within the overall unit cabinet, insulate the draft diverter box with insulation as described in section 6.4.c before the cool-down and heat-up tests described in sections 9.5 and 9.6, respectively, of ASHRAE 103–1993. However, do not apply the insulation for the jacket loss test (if conducted) described in section 8.6 of ASHRAE 103–1993 or the steady-state test described in section 9.1 of ASHRAE 103–1993.
6.5 Condensate collection. Attach condensate drain lines to the unit as specified in the I&O manual. Maintain a continuous downward slope of drain lines from the unit. Additional precautions (such as eliminating any line configuration or position that would otherwise restrict or block the flow of condensate or checking to ensure a proper connection with condensate drain spout that allows for unobstructed flow) must be taken to facilitate uninterrupted flow of condensate during the test. Collection containers must be glass or polished stainless steel to facilitate removal of interior deposits. The collection container must have a vent opening to the atmosphere.
7. Testing conditions. The testing conditions must be as specified in section 8 of ASHRAE 103–1993 (except for the excluded sub-sections as enumerated at § 430.3(g)(15)); and as specified in sections 7.1 to 7.9 of this appendix, respectively.
7.1 Fuel supply, gas. In conducting the tests specified herein, gases with characteristics as shown in Table 1 of ASHRAE 103–1993 shall be used. Maintain the gas supply, ahead of all controls for a furnace, at a test pressure between the normal and increased values shown in Table 1 of ASHRAE 103–1993. Maintain the regulator outlet pressure at a level approximating that recommended in the I&O manual, as defined in section 2.6 of this appendix, or, in the absence of such recommendation, to the nominal regulator settings used when the product is shipped by the manufacturer. Use a gas having a specific gravity as shown in Table 1 of ASHRAE 103–1993 and with a higher heating value within ±5% of the higher heating value shown in Table 1 of ASHRAE 103–1993. Determine the actual higher heating value in Btu per standard cubic foot for the gas to be used in the test within an error no greater than 1%.
7.2 Gas burner. Adjust the burners of gas-fired furnaces to their maximum Btu input ratings at the normal test pressure specified by section 7.1 of this appendix. Correct the burner input rate to reflect gas characteristics at a temperature of 60 °F and atmospheric pressure of 30 in of Hg and adjust down to within ±2 percent of the hourly Btu nameplate input rating specified by the manufacturer as measured during the steady-state performance test in section 8 of this appendix. Set the primary air shutters in accordance with the I&O manual to give a good flame at this condition. If, however, the setting results in the deposit of carbon on the burners during any test specified herein, the tester shall adjust the shutters and burners until no more carbon is deposited and shall perform the tests again with the new settings (see Figure 9 of ASHRAE 103–1993). After the steady-state performance test has been started, do not make additional adjustments to the burners during the required series of performance tests specified in section 9 of ASHRAE 103–1993. If a vent-limiting means is provided on a gas pressure regulator, keep it in place during all tests.
7.3 Modulating gas burner adjustment at reduced input rate. For gas-fired furnaces equipped with modulating-type controls, adjust the controls to operate the unit at the nameplate minimum input rate. If the modulating control is of a non-automatic type, adjust the control to the setting recommended in the I&O manual. In the absence of such recommendation, the midpoint setting of the non-automatic control shall be used as the setting for determining the reduced fuel input rate. Start the furnace by turning the safety control valve to the “ON” position.
7.4 Oil burner. Adjust the burners of oil-fired furnaces to give a CO2 reading specified in the I&O manual and an hourly Btu input during the steady-state performance test described in section 8 of this appendix. Ensure the hourly BTU input is within ±2% of the normal hourly Btu input rating as specified in the I&O manual. Smoke in the flue may not exceed a No. 1 smoke during the steady-state performance test as measured by the procedure in ASTM D2156R13). Maintain the average draft over the fire and in the flue during the steady-state performance test at the value specified in the I&O manual. Do not allow draft fluctuations exceeding 0.005 in. water. Do not make additional adjustments to the burner during the required series of performance tests. The instruments and measuring apparatus for this test are described in section 6 of this appendix and shown in Figure 8 of ASHRAE 103–1993.
7.5 Temperature Rise Targets. Adjust air throughputs to achieve a temperature rise that is the higher of a and b, below, unless c applies. A tolerance of ±2 °F is permitted.
(a) 15 °F less than the nameplate maximum temperature rise or
(b) 15 °F higher than the minimum temperature rise specified in the I&O manual.
(c) A furnace with a non-adjustable air temperature rise range and an automatically controlled airflow that does not permit a temperature rise range of 30 °F or more must be tested at the midpoint of the rise range.
7.6 Temperature Rise Adjustments. Establish the temperature rise specified in section 7.5 of this appendix by adjusting the circulating airflow. This adjustment must be accomplished by symmetrically restricting the outlet air duct and varying blower speed selection to obtain the desired temperature rise and minimum external static pressure, as specified in Table 4 of ASHRAE 103–1993. If the required temperature rise cannot be obtained at the minimum specified external static pressure by adjusting blower speed selection and duct outlet restriction, then the following applies.
(a) If the resultant temperature rise is less than the required temperature rise, vary the blower speed by gradually adjusting the blower voltage so as to maintain the minimum external static pressure listed in Table 4 of ASHRAE 103–1993. The airflow restrictions shall then remain unchanged. If static pressure must be varied to prevent unstable blower operation, then increase the static pressure until blower operation is stabilized, except that the static pressure must not exceed the maximum external static pressure as specified by the manufacturer in the I&O manual.
(b) If the resultant temperature rise is greater than the required temperature rise, then the unit can be tested at a higher temperature rise value, but one not greater than nameplate maximum temperature rise. In order not to exceed the maximum temperature rise, the speed of a direct-driven blower may be increased by increasing the circulating air blower motor voltage.
7.7 Measurement of jacket surface temperature. Divide the jacket of the furnace into 6-inch squares when practical, and otherwise into 36-square-inch regions comprising 4-inch by 9-inch or 3-inch by 12-inch sections, and determine the surface temperature at the center of each square or section with a surface thermocouple. Record the surface temperature of the 36-square-inch areas in groups where the temperature differential of the 36-square-inch areas is less than 10 °F for temperature up to 100 °F above room temperature, and less than 20 °F for temperatures 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 103–1993).
7.8 Installation of vent system. Keep the vent or air intake system supplied by the manufacturer in place during all tests. Test units intended for installation with a variety of vent pipe lengths with the minimum vent length as specified in the I&O manual, or a 5-ft. flue pipe if there are no recommendations in the I&O manual. Do not connect a furnace employing a direct vent system to a chimney or induced-draft source. Vent combustion products solely by using the venting incorporated in the furnace and the vent or air intake system supplied by the manufacturer. For units that are not designed to significantly preheat the incoming air, see section 7.4 of this appendix and Figure 4a or 4b of ASHRAE 103–1993. For units that do significantly preheat the incoming air, see Figure 4c or 4d of ASHRAE 103–1993.
7.9 Additional optional method of testing for determining DP and DF for furnaces. On units whose design is such that there is no measurable airflow through the combustion chamber and heat exchanger when the burner(s) is (are) off as determined by the optional test procedure in section 7.9.1 of this appendix, DF and DP may be set equal to 0.05.
7.9.1 Optional test method for indicating the absence of flow through the heat exchanger. Manufacturers may use the following test protocol to determine whether air flows through the combustion chamber and heat exchanger when the burner(s) is (are) off. The minimum default draft factor may be used only for units determined pursuant to this protocol to have no airflow through the combustion chamber and heat exchanger.
126.96.36.199 Test apparatus. Use a smoke stick that produces smoke that is easily visible and has a density less than or approximately equal to air. Use a smoke stick that produces smoke that is non-toxic to the test personnel and produces gas that is unreactive with the environment in the test chamber.
188.8.131.52 Test conditions. Minimize all air currents and drafts in the test chamber, including turning off ventilation if the test chamber is mechanically ventilated. Wait at least two minutes following the termination of the furnace on-cycle before beginning the optional test method for indicating the absence of flow through the heat exchanger.
184.108.40.206 Location of the test apparatus. After all air currents and drafts in the test chamber have been eliminated or minimized, position the smoke stick based on the following equipment configuration:
(a) For horizontal combustion air intakes, approximately 4 inches from the vertical plane at the termination of the intake vent and 4 inches below the bottom edge of the combustion air intake; or
(b) for vertical combustion air intakes, approximately 4 inches horizontal from vent perimeter at the termination of the intake vent and 4 inches down (parallel to the vertical axis of the vent).
220.127.116.11 Duration of test. Establish the presence of smoke from the smoke stick and then monitor the direction of the smoke flow for no less than 30 seconds.
18.104.22.168 Test results. During visual assessment, determine whether there is any draw of smoke into the combustion air intake vent.
(a) If absolutely no smoke is drawn into the combustion air intake, the furnace meets the requirements to allow use of the minimum default draft factor pursuant to section 7.9 of this appendix.
(b) If there is any smoke drawn into the intake, proceed with the methods of testing as prescribed in section 8.8 of ASHRAE 103–1993.
8. Test procedure. Conduct testing and measurements as specified in section 9 of ASHRAE 103–1993 (except for the excluded sub-sections as enumerated at § 430.3(g)(15)); and as specified in sections 8.1 through 8.10 of this appendix. Section 8.4 of this appendix may be used in lieu of section 9.2 of ASHRAE 103–1993.
8.1 Fuel input. For gas units, measure and record the steady-state gas input rate in Btu/hr, including pilot gas, corrected to standard conditions of 60 °F and 30 in. Hg. Use measured values of gas temperature and pressure at the meter and barometric pressure to correct the metered gas flow rate to the above standard conditions. For oil units, measure and record the steady-state fuel input rate.
8.2 Electrical input. During the steady-state test, perform a single measurement of all of the electrical power involved in burner operation (PE), including energizing the ignition system, controls, gas valve or oil control valve, and draft inducer, if applicable.
During the steady-state test, perform a single measurement of the electrical power to the circulating air blower (BE).
8.3 Input to interrupted ignition device. For burners equipped with an interrupted ignition device, record the nameplate electric power used by the ignition device, PEIG, or record that PEIG = 0.4 kW if no nameplate power input is provided. Record the nameplate ignition device on-time interval, tIG, or, if the nameplate does not provide the ignition device on-time interval, measure the on-time interval with a stopwatch at the beginning of the test, starting when the burner is turned on. Set tIG = 0 and PEIG = 0 if the device on-time interval is less than or equal to 5 seconds after the burner is on.
8.4 Optional test procedures for condensing furnaces, measurement of condensate during the establishment of steady-state conditions. For units with step-modulating or two-stage controls, conduct the test at both the maximum and reduced inputs. In lieu of collecting the condensate immediately after the steady state conditions have been reached as required by section 9.2 of ASHRAE 103–1993, condensate may be collected during the establishment of steady state conditions as defined by section 22.214.171.124 of ASHRAE 103–1993. Perform condensate collection for at least 30 minutes. Measure condensate mass immediately at the end of the collection period to prevent evaporation loss from the sample. Record fuel input for the 30-minute condensate collection test period. Observe and record fuel higher heating value (HHV), temperature, and pressures necessary for determining fuel energy input (Qc,ss). Measure the fuel quantity and HHV with errors no greater than 1%. The humidity for the room air shall at no time exceed 80%. Determine the mass of condensate for the establishment of steady state conditions (Mc,ss) in pounds by subtracting the tare container weight from the total container and condensate weight measured at the end of the 30-minute condensate collection test period.
8.5 Cool-down test for gas- and oil-fueled gravity and forced-air central furnaces without stack dampers. Turn off the main burner after completing steady-state testing, and measure the flue gas temperature by means of the thermocouple grid described in section 7.6 of ASHRAE 103–1993 at 1.5 minutes (TF,OFF(t3)) and 9 minutes (TF,OFF(t4)) after shutting off the burner. When taking these temperature readings, the integral draft diverter must remain blocked and insulated, and the stack restriction must remain in place. On atmospheric systems with an integral draft diverter or draft hood and equipped with either an electromechanical inlet damper or an electromechanical flue damper that closes within 10 seconds after the burner shuts off to restrict the flow through the heat exchanger in the off-cycle, bypass or adjust the control for the electromechanical damper so that the damper remains open during the cool-down test.
For furnaces that employ post-purge, measure the length of the post-purge period with a stopwatch. Record the time from burner “OFF” to combustion blower “OFF” (electrically de-energized) as tP. If the measured tP is less than or equal to 30 seconds, set tP at 0 and conduct the cool-down test as if there is no post-purge. If tP is prescribed by the I&O manual or measured to be greater than 180 seconds, stop the combustion blower at 180 seconds and use that value for tP. Measure the flue gas temperature by means of the thermocouple grid described in section 7.6 of ASHRAE 103–1993 at the end of the post-purge period, tP(TF,OFF (tP)), and at the time (1.5 + tP) minutes (TF,OFF(t3)) and (9.0 + tP) minutes (TF,OFF(t4)) after the main burner shuts off.
8.6 Cool-down test for gas- and oil-fueled gravity and forced-air central furnaces without stack dampers and with adjustable fan control. For a furnace with adjustable fan control, measure the time delay between burner shutdown and blower shutdown, t +. This time delay, t +, will be 3.0 minutes for non-condensing furnaces or 1.5 minutes for condensing furnaces or until the supply air temperature drops to a value of 40 °F above the inlet air temperature, whichever results in the longest fan on-time. For a furnace without adjustable fan control or with the type of adjustable fan control whose range of adjustment does not allow for the time delay, t +, specified above, bypass the fan control and manually control the fan to allow for the appropriate delay time as specified in section 126.96.36.199 of ASHRAE 103–1993. For a furnace that employs a single motor to drive both the power burner and the indoor air circulating blower, the power burner and indoor air circulating blower must be stopped at the same time.
8.8 Calculation options. The rate of the flue gas mass flow through the furnace and the factors DP, DF, and DS are calculated by the equations in sections 11.6.1, 11.6.2, 11.6.3, 11.6.4, 11.7.1, and 11.7.2 of ASHRAE 103–1993. On units whose design is such that there is no measurable airflow through the combustion chamber and heat exchanger when the burner(s) is (are) off (as determined by the optional test procedure in section 7.9 of this appendix), DF and DP may be set equal to 0.05.
8.9 Optional test procedures for condensing furnaces that have no off-period flue losses. For units that have applied the test method in section 7.9 of this appendix to determine that no measurable airflow exists through the combustion chamber and heat exchanger during the burner off-period and having post-purge periods of less than 5 seconds, the cool-down and heat-up tests specified in sections 9.5 and 9.6 of ASHRAE 103–1993 may be omitted. In lieu of conducting the cool-down and heat-up tests, the tester may use the losses determined during the steady-state test described in section 9.1 of ASHRAE 103–1993 when calculating heating seasonal efficiency, EffyHS.
8.10 Measurement of electrical standby and off mode power.
8.10.1 Standby power measurement. With all electrical auxiliaries of the furnace not activated, measure the standby power (PW,SB) in accordance with the procedures in IEC 62301, except that section 8.5, Room Ambient Temperature, of ASHRAE 103–1993 and the voltage provision of section 188.8.131.52, Electrical Supply, of ASHRAE 103–1993 shall apply in lieu of the corresponding provisions of IEC 62301 at section 4.2, Test room, and the voltage specification of section 4.3, Power supply. Frequency shall be 60Hz. Clarifying further, IEC 62301 section 4.4, Power measurement instruments, and Section 5, Measurements, apply in lieu of ASHRAE 103–1993 section 6.10, Energy Flow Rate. Measure the wattage so that all possible standby mode wattage for the entire appliance is recorded, not just the standby mode wattage of a single auxiliary. Round the recorded standby power (PW,SB) to the second decimal place, except for loads greater than or equal to 10W, which must be recorded to at least three significant figures.
8.10.2 Off mode power measurement. If the unit is equipped with an off switch or there is an expected difference between off mode power and standby mode power, measure off mode power (PW,OFF) in accordance with the standby power procedures in IEC 62301, except that section 8.5, Room Ambient Temperature, of ASHRAE 103–1993 and the voltage provision of section 184.108.40.206, Electrical Supply, of ASHRAE 103–1993 shall apply in lieu of the corresponding provisions of IEC 62301 at section 4.2, Test room, and the voltage specification of section 4.3, Power supply. Frequency shall be 60Hz. Clarifying further, IEC 62301 section 4.4, Power measurement instruments, and section 5, Measurements, apply for this measurement in lieu of ASHRAE 103–1993 section 6.10, Energy Flow Rate. Measure the wattage so that all possible off mode wattage for the entire appliance is recorded, not just the off mode wattage of a single auxiliary. If there is no expected difference in off mode power and standby mode power, let PW,OFF = PW,SB, in which case no separate measurement of off mode power is necessary. Round the recorded off mode power (PW,OFF) to the second decimal place, except for loads greater than or equal to 10W, in which case round the recorded value to at least three significant figures.
9. Nomenclature. Nomenclature includes the nomenclature specified in section 10 of ASHRAE 103–1993 and the following additional variables:
10. Calculation of derived results from test measurements. Perform calculations as specified in section 11 of ASHRAE 103–1993 (except for the excluded sub-sections as enumerated at § 430.3(g)(15)); and as specified in sections 10.1 through 10.11 and Figure 1 of this appendix.
10.1 Annual fuel utilization efficiency. The annual fuel utilization efficiency (AFUE) is as defined in sections 11.2.12 (non-condensing systems), 11.3.12 (condensing systems), 11.4.12 (non-condensing modulating systems) and 11.5.12 (condensing modulating systems) of ASHRAE 103–1993, except for the definition for the term EffyHS in the defining equation for AFUE. EffyHS is defined as:
10.2 Part-load efficiency at reduced fuel input rate. If the option in section 8.9 of this appendix is not employed, calculate the part-load efficiency at the reduced fuel input rate, EffyU,R, for condensing furnaces equipped with either step-modulating or two-stage controls, expressed as a percent and defined as: