10 CFR Appendix Z to Subpart B of Part 430, Uniform Test Method for Measuring the Energy Consumption of External Power Supplies

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Appendix Z to Subpart B of Part 430 - Uniform Test Method for Measuring the Energy Consumption of External Power Supplies

Starting on February 21, 2016, any representations made with respect to the energy use or efficiency of external power supplies must be made in accordance with the results of testing pursuant to this appendix. Prior to February 21, 2016, representations made with respect to the energy use or efficiency of external power supplies must be made in accordance with this appendix or Appendix Z as it appeared at 10 CFR part 430, subpart B, Appendix Z as contained in the 10 CFR parts 200 to 499 edition revised as of January 1, 2015. Because representations must be made in accordance with tests conducted pursuant to this appendix as of February 21, 2016, manufacturers may wish to begin using this test procedure as soon as possible.

1. Scope.

This appendix covers the test requirements used to measure the energy consumption of direct operation external power supplies and indirect operation Class A external power supplies subject to the energy conservation standards set forth at § 430.32(w)(1).

2. Definitions: The following definitions are for the purposes of understanding terminology associated with the test method for measuring external power supply energy consumption. For clarity on any other terminology used in the test method, please refer to IEC Standard 60050 or IEEE Standard 100. (Reference for guidance only, see § 430.4.)

a. Active mode means the mode of operation when the external power supply is connected to the main electricity supply and the output is (or “all outputs are” for a multiple-voltage external power supply) connected to a load (or “loads” for a multiple-voltage external power supply).

b. Active mode efficiency is the ratio, expressed as a percentage, of the total real output power produced by a power supply to the real input power required to produce it. (Reference for guidance only, see IEEE Standard 1515-2000, 4.3.1.1, § 430.4.)

c. Active power (P) (also real power) means the average power consumed by a unit. For a two terminal device with current and voltage waveforms i(t) and v(t) which are periodic with period T, the real or active power P is:

d. Ambient temperature means the temperature of the ambient air immediately surrounding the unit under test.

e. Apparent power (S) is the product of RMS voltage and RMS current (VA).

f. Average Active-Mode Efficiency means the average of the loading conditions (100 percent, 75 percent, 50 percent, and 25 percent of its nameplate output current) for which it can sustain the output current.

g. IEC 62301 means the test standard published by the International Electrotechnical Commission, titled “Household electrical appliances - Measurement of standby power,” Publication 62301 (Edition 2.0 2011-01) (incorporated by reference; see § 430.3).

h. Instantaneous power means the product of the instantaneous voltage and instantaneous current at a port (the terminal pair of a load).

i. Manual on-off switch is a switch activated by the user to control power reaching the device. This term does not apply to any mechanical, optical, or electronic switches that automatically disconnect mains power from the device when a load is disconnected from the device, or that control power to the load itself.

j. Minimum output current means the minimum current that must be drawn from an output bus for an external power supply to operate within its specifications.

k. Multiple-voltage external power supply means an external power supply that is designed to convert line voltage AC input into more than one simultaneous lower-voltage output.

l. Nameplate input frequency means the AC input frequency of the power supply as specified on the manufacturer's label on the power supply housing.

m. Nameplate input voltage means the AC input voltage of the power supply as specified on the manufacturer's label on the power supply housing.

n. Nameplate output current means the current output of the power supply as specified on the manufacturer's label on the power supply housing (either DC or AC) or, if absent from the housing, as provided by the manufacturer.

o. Nameplate output power means the power output of the power supply as specified on the manufacturer's label on the power supply housing or, if absent from the housing, as specified in documentation provided by the manufacturer.

p. Nameplate output voltage means the voltage output of the power supply as specified on the manufacturer's label on the power supply housing (either DC or AC).

q. No-load mode means the mode of operation when an external power supply is connected to the main electricity supply and the output is (or “all outputs are” for a multiple-voltage external power supply) not connected to a load (or “loads” for a multiple-voltage external power supply).

r. Off mode is the condition, applicable only to units with manual on-off switches, in which the external power supply is (1) connected to the main electricity supply; (2) the output is not connected to any load; and (3) all manual on-off switches are turned off.

s. Output bus means any of the outputs of the power supply to which loads can be connected and from which power can be drawn, as opposed to signal connections used for communication.

t. Single-voltage external AC-AC power supply means an external power supply that is designed to convert line voltage AC input into lower voltage AC output and is able to convert to only one AC output voltage at a time.

u. Single-voltage external AC-DC power supply means an external power supply that is designed to convert line voltage AC input into lower-voltage DC output and is able to convert to only one DC output voltage at a time.

v. Standby mode means the condition in which the external power supply is in no-load mode and, for external power supplies with manual on-off switches, all such switches are turned on.

w. Switch-selectable single voltage external power supply means a single-voltage AC-AC or AC-DC power supply that allows users to choose from more than one output voltage.

x. Total harmonic distortion, expressed as a percentage, is the RMS value of an AC signal after the fundamental component is removed and interharmonic components are ignored, divided by the RMS value of the fundamental component. THD of current is defined as:

where In is the RMS value of the nth harmonic of the current signal.

y. True power factor (PF) is the ratio of the active power (P) consumed in watts to the apparent power (S), drawn in volt-amperes.

This definition of power factor includes the effect of both distortion and displacement.

z. Unit under test is the external power supply being tested.

3. Test Apparatus and General Instructions:

(a) Single-Voltage External Power Supply.

(i) Any power measurements recorded, as well as any power measurement equipment utilized for testing, shall conform to the uncertainty and resolution requirements outlined in Section 4, “General conditions for measurements,” as well as Annexes B, “Notes on the measurement of low power modes,” and D, “Determination of uncertainty of measurement,” of IEC 62301 (incorporated by reference; see § 430.3).

(ii) As is specified in IEC 62301 (incorporated by reference; see § 430.3), the tests shall be carried out in a room that has an air speed close to the unit under test (UUT) of ≤0.5 m/s. The ambient temperature shall be maintained at 20 ± 5 °C throughout the test. There shall be no intentional cooling of the UUT by use of separately powered fans, air conditioners, or heat sinks. The UUT shall be tested on a thermally non-conductive surface. Products intended for outdoor use may be tested at additional temperatures, provided those are in addition to the conditions specified above and are noted in a separate section on the test report.

(iii) If the UUT is intended for operation on AC line-voltage input in the United States, it shall be tested at 115 V at 60 Hz. If the UUT is intended for operation on AC line-voltage input but cannot be operated at 115 V at 60 Hz, it shall not be tested. The input voltage shall be within ±1 percent of the above specified voltage.

(iv) The input voltage source must be capable of delivering at least 10 times the nameplate input power of the UUT as is specified in IEEE 1515-2000 (Referenced for guidance only, see § 430.4). Regardless of the AC source type, the THD of the supply voltage when supplying the UUT in the specified mode must not exceed 2%, up to and including the 13th harmonic (as specified in IEC 62301). The peak value of the test voltage must be within 1.34 and 1.49 times its RMS value (as specified in IEC 62301 (incorporated by reference; see § 430.3)).

(v) Select all leads used in the test set-up as specified in Table B.2 - “Commonly used values for wire gages and related voltage drops” in IEEE 15152000.

(b) Multiple-Voltage External Power Supply. Unless otherwise specified, measurements shall be made under test conditions and with equipment specified below.

(i) Verifying Accuracy and Precision of Measuring Equipment

(A) Any power measurements recorded, as well as any power measurement equipment utilized for testing, must conform to the uncertainty and resolution requirements outlined in Section 4, “General conditions for measurements”, as well as Annexes B, “Notes on the measurement of low power modes”, and D, “Determination of uncertainty of measurement”, of IEC 62301 (incorporated by reference; see § 430.3).

(B) [Reserved]

(ii) Setting Up the Test Room

All tests shall be carried out in a room with an air speed immediately surrounding the UUT of ≤0.5 m/s. The ambient temperature shall be maintained at 20 °C ±5 °C throughout the test. There shall be no intentional cooling of the UUT such as by use of separately powered fans, air conditioners, or heat sinks. The UUT shall be conditioned, rested, and tested on a thermally non-conductive surface. A readily available material such as Styrofoam will be sufficient.

(iii) Verifying the UUT's Input Voltage and Input Frequency

(A) If the UUT is intended for operation on AC line-voltage input in the United States, it shall be tested at 115 V at 60 Hz. If the UUT is intended for operation on AC line-voltage input but cannot be operated at 115 V at 60 Hz, it shall not be tested. The input voltage shall be within ±1 percent of the above specified voltage.

(B) If the input voltage is AC, the input frequency shall be within ±1 percent of the specified frequency. The THD of the input voltage shall be ≤2 percent, up to and including the 13th harmonic. The crest factor of the input voltage shall be between 1.34 and 1.49.

4. Test Measurement:

(a) Single-Voltage External Power Supply

(i) Standby Mode and Active-Mode Measurement.

(A) Any built-in switch in the UUT controlling power flow to the AC input must be in the “on” position for this measurement, and note the existence of such a switch in the final test report. Test power supplies packaged for consumer use to power a product with the DC output cord supplied by the manufacturer. There are two options for connecting metering equipment to the output of this type of power supply: Cut the cord immediately adjacent to the DC output connector, or attach leads and measure the efficiency from the output connector itself. If the power supply is attached directly to the product that it is powering, cut the cord immediately adjacent to the powered product and connect DC measurement probes at that point. Any additional metering equipment such as voltmeters and/or ammeters used in conjunction with resistive or electronic loads must be connected directly to the end of the output cable of the UUT. If the product has more than two output wires, including those that are necessary for controlling the product, the manufacturer must supply a connection diagram or test fixture that will allow the testing laboratory to put the unit under test into active-mode. Figure 1 provides one illustration of how to set up an EPS for test; however, the actual test setup may vary pursuant to the requirements of this paragraph.

(B) External power supplies must be tested in their final, completed configuration in order to represent their measured efficiency on product labels or specification sheets. Although the same procedure may be used to test the efficiency of a bare circuit board power supply prior to its incorporation into a finished housing and the attachment of its DC output cord, the efficiency of the bare circuit board power supply may not be used to characterize the efficiency of the final product (once enclosed in a case and fitted with a DC output cord). For example, a power supply manufacturer or component manufacturer may wish to assess the efficiency of a design that it intends to provide to an OEM for incorporation into a finished external power supply, but these results may not be used to represent the efficiency of the finished external power supply.

(C) All single voltage external AC-DC power supplies have a nameplate output current. This is the value used to determine the four active-mode load conditions and the no load condition required by this test procedure. The UUT shall be tested at the following load conditions:

Table 1 - Loading Conditions for a Single-Voltage Unit Under Test

Percentage of Nameplate Output Current
Load Condition 1 100% of Nameplate Output Current ±2%.
Load Condition 2 75% of Nameplate Output Current ±2%.
Load Condition 3 50% of Nameplate Output Current ±2%.
Load Condition 4 25% of Nameplate Output Current ±2%.
Load Condition 5 0%.

The 2% allowance is of nameplate output current, not of the calculated current value. For example, a UUT at Load Condition 3 may be tested in a range from 48% to 52% of rated output current. Additional load conditions may be selected at the technician's discretion, as described in IEEE 1515-2000 (Referenced for guidance only, see § 430.4), but are not required by this test procedure. For Loading Condition 5, place the UUT in no-load mode, disconnect any additional signal connections to the UUT, and measure input power.

1. Where the external power supply lists both an instantaneous and continuous output current, test the external power supply at the continuous condition only.

2. If an external power supply cannot sustain output at one or more of loading conditions 1-4 as specified in Table 1, test the external power supply only at the loading conditions for which it can sustain output. In these cases, the average active mode efficiency is the average of the loading conditions for which it can sustain the output.

(D) Test switch-selectable single-voltage external power supplies twice - once at the highest nameplate output voltage and once at the lowest.

(E) Test adaptive external power supplies twice - once at the highest achievable output voltage and once at the lowest.

(F) In order to load the power supply to produce all four active-mode load conditions, use a set of variable resistive or electronic loads. Although these loads may have different characteristics than the electronic loads power supplies are intended to power, they provide standardized and readily repeatable references for testing and product comparison. Note that resistive loads need not be measured precisely with an ohmmeter; simply adjust a variable resistor to the point where the ammeter confirms that the desired percentage of nameplate output current is flowing. For electronic loads, adjust the desired output current in constant current (CC) mode rather than adjusting the required output power in constant power (CP) mode.

(G) As noted in IEC 62301 (incorporated by reference; see § 430.3), instantaneous measurements are appropriate when power readings are stable in a particular load condition. Operate the UUT at 100% of nameplate current output for at least 30 minutes immediately prior to conducting efficiency measurements. After this warm-up period, monitor AC input power for a period of 5 minutes to assess the stability of the UUT. If the power level does not drift by more than 5% from the maximum value observed, the UUT is considered stable and the measurements should be recorded at the end of the 5-minute period. Measure subsequent load conditions under the same 5-minute stability parameters. Note that only one warm-up period of 30 minutes is required for each UUT at the beginning of the test procedure. If the AC input power is not stable over a 5-minute period, follow the guidelines established by IEC 62301 for measuring average power or accumulated energy over time for both AC input and DC output. Conduct efficiency measurements in sequence from Load Condition 1 to Load Condition 5 as indicated in Table 1. If testing of additional, optional load conditions is desired, that testing should be conducted in accordance with this test procedure and subsequent to completing the sequence described above.

(H) Calculate efficiency by dividing the UUT's measured DC output power at a given load condition by the true AC input power measured at that load condition. Calculate average efficiency as the arithmetic mean of the efficiency values calculated at Test Conditions 1, 2, 3, and 4 in Table 1, and record this value. Average efficiency for the UUT is a simple arithmetic average of active-mode efficiency values, and is not intended to represent weighted average efficiency, which would vary according to the duty cycle of the product powered by the UUT.

(I) Power consumption of the UUT at each Load Condition 1-4 is the difference between the DC output power (W) at that Load Condition and the AC input power (W) at that Load Condition. The power consumption of Load Condition 5 (no load) is equal to the AC input power (W) at that Load Condition.

(ii) Off-Mode Measurement - If the external power supply UUT incorporates manual on-off switches, place the UUT in off-mode, and measure and record its power consumption at “Load Condition 5” in Table 1. The measurement of the off-mode energy consumption must conform to the requirements specified in paragraph 4(a)(i) of this appendix, except that all manual on-off switches must be placed in the “off” position for the off-mode measurement. The UUT is considered stable if, over 5 minutes with samples taken at least once every second, the AC input power does not drift from the maximum value observed by more than 1 percent or 50 milliwatts, whichever is greater. Measure the off-mode power consumption of a switch-selectable single-voltage external power supply twice - once at the highest nameplate output voltage and once at the lowest.

(b) Multiple-Voltage External Power Supply - Power supplies must be tested with the output cord packaged with the unit for sale to the consumer, as it is considered part of the unit under test. There are two options for connecting metering equipment to the output of this type of power supply: cut the cord immediately adjacent to the output connector or attach leads and measure the efficiency from the output connector itself. If the power supply is attached directly to the product that it is powering, cut the cord immediately adjacent to the powered product and connect output measurement probes at that point. The tests should be conducted on the sets of output wires that constitute the output busses. If the product has additional wires, these should be left electrically disconnected unless they are necessary for controlling the product. In this case, the manufacturer shall supply a connection diagram or test fixture that will allow the testing laboratory to put the unit under test into active mode.

(i) Standby-Mode and Active-Mode Measurement - The measurement of the multiple-voltage external power supply standby mode (also no-load-mode) energy consumption and active-mode efficiency shall be as follows:

(A) Loading conditions and testing sequence. (1) If the unit under test has on-off switches, all switches shall be placed in the “on” position. Loading criteria for multiple-voltage external power supplies shall be based on nameplate output current and not on nameplate output power because output voltage might not remain constant.

(2) The unit under test shall operate at 100 percent of nameplate current output for at least 30 minutes immediately before conducting efficiency measurements.

(3) After this warm-up period, the technician shall monitor AC input power for a period of 5 minutes to assess the stability of the unit under test. If the power level does not drift by more than 1 percent from the maximum value observed, the unit under test can be considered stable and measurements can be recorded at the end of the 5-minute period. Measurements at subsequent loading conditions, listed in Table 1, can then be conducted under the same 5-minute stability guidelines. Only one warm-up period of 30 minutes is required for each unit under test at the beginning of the test procedure.

(4) If AC input power is not stable over a 5-minute period, the technician shall follow the guidelines established by IEC Standard 62301 for measuring average power or accumulated energy over time for both input and output. (Reference for guidance only, see § 430.4).

(5) The unit under test shall be tested at the loading conditions listed in Table 1, derated per the proportional allocation method presented in the following section.

Table 1 - Loading Conditions for Unit Under Test

Loading Condition 1 100% of Derated Nameplate Output Current ±2%.
Loading Condition 2 75% of Derated Nameplate Output Current ±2%.
Loading Condition 3 50% of Derated Nameplate Output Current ±2%.
Loading Condition 4 25% of Derated Nameplate Output Current ±2%.
Loading Condition 5 0%.

(6) Input and output power measurements shall be conducted in sequence from Loading Condition 1 to Loading Condition 4, as indicated in Table 1. For Loading Condition 5, the unit under test shall be placed in no-load mode, any additional signal connections to the unit under test shall be disconnected, and input power shall be measured.

(B) Proportional allocation method for loading multiple-voltage external power supplies. For power supplies with multiple voltage busses, defining consistent loading criteria is difficult because each bus has its own nameplate output current. The sum of the power dissipated by each bus loaded to its nameplate output current may exceed the overall nameplate output power of the power supply. The following proportional allocation method must be used to provide consistent loading conditions for multiple-voltage external power supplies. For additional explanation, please refer to section 6.1.1 of the California Energy Commission's “Proposed Test Protocol for Calculating the Energy Efficiency of Internal Ac-Dc Power Supplies Revision 6.2,” November 2007.

(1) Consider a multiple-voltage power supply with N output busses, and nameplate output voltages V1, * * *, VN, corresponding output current ratings I1, * * *, IN, and a nameplate output power P. Calculate the derating factor D by dividing the power supply nameplate output power P by the sum of the nameplate output powers of the individual output busses, equal to the product of bus nameplate output voltage and current IiVi, as follows:

(2) If D ≥1, then loading every bus to its nameplate output current does not exceed the overall nameplate output power for the power supply. In this case, each output bus will simply be loaded to the percentages of its nameplate output current listed in Table 1. However, if D <1, it is an indication that loading each bus to its nameplate output current will exceed the overall nameplate output power for the power supply. In this case, and at each loading condition, each output bus will be loaded to the appropriate percentage of its nameplate output current listed in Table 1, multiplied by the derating factor D.

(C) Minimum output current requirements. Depending on their application, some multiple-voltage power supplies may require a minimum output current for each output bus of the power supply for correct operation. In these cases, ensure that the load current for each output at Loading Condition 4 in Table 1 is greater than the minimum output current requirement. Thus, if the test method's calculated load current for a given voltage bus is smaller than the minimum output current requirement, the minimum output current must be used to load the bus. This load current shall be properly recorded in any test report.

(D) Test loads. Active loads such as electronic loads or passive loads such as rheostats used for efficiency testing of the unit under test shall be able to maintain the required current loading set point for each output voltage within an accuracy of ±0.5 percent. If electronic load banks are used, their settings should be adjusted such that they provide a constant current load to the unit under test.

(E) Efficiency calculation. Efficiency shall be calculated by dividing the measured active output power of the unit under test at a given loading condition by the active AC input power measured at that loading condition. Efficiency shall be calculated at each Loading Condition (1, 2, 3, and 4, in Table 1) and be recorded separately.

(F) Power consumption calculation. Power consumption of the unit under test at Loading Conditions 1, 2, 3, and 4 is the difference between the active output power at that Loading Condition and the active AC input power at that Loading Condition. The power consumption of Loading Condition 5 (no-load) is equal to the AC active input power at that Loading Condition.

(ii) Off Mode Measurement - If the multiple-voltage external power supply unit under test incorporates any on-off switches, the unit under test shall be placed in off mode and its power consumption in off mode measured and recorded. The measurement of the off mode energy consumption shall conform to the requirements specified in paragraph (4)(b)(i) of this appendix. Note that the only loading condition that will be measured for off mode is “Loading Condition 5” in paragraph (A), “Loading conditions and testing sequence”, except that all manual on-off switches shall be placed in the off position for the measurement.

[71 FR 71366, Dec. 8, 2006, as amended at 74 FR 12066, Mar. 23, 2009; 74 FR 13334, Mar. 27, 2009; 76 FR 31782, June 1, 2011; 80 FR 51441, Aug. 25, 2015]

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  • 2017-01-06; vol. 82 # 4 - Friday, January 6, 2017
    1. 82 FR 1608 - Energy Conservation Program: Energy Conservation Standards for Consumer Central Air Conditioners and Heat Pumps
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      Notice of proposed rulemaking.
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  • 2017-01-06; vol. 82 # 4 - Friday, January 6, 2017
    1. 82 FR 1786 - Energy Conservation Program: Energy Conservation Standards for Residential Central Air Conditioners and Heat Pumps
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      DEPARTMENT OF ENERGY, Office of Energy Efficiency and Renewable Energy
      Direct final rule.
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