ASHRAE Standard 41.11 2023

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ASHRAE Standard 41.11-2023 — Standard Methods for Power Measurement (ANSI Approved)

Published By	Publication Date	Number of Pages
ASHRAE	2023	32

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Description

ASHRAE Standard 41.11 prescribes methods for power measurements under laboratory and field conditions when testing heating, ventilating, air-conditioning, and refrigerating systems and components.

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PDF Pages	PDF Title
1	ANSI/ASHRAE Standard 41.11-2023
3	Contents
4	Foreword 1. Purpose 2. Scope 3. Definitions
6	4. Classifications 4.1 Power Measurement Application. Power measurements that are within the scope of this standard are classified as one of the types in Sections 4.1.1 and 4.1.2. 4.2 Electrical Load Type. Electrical load configurations for electrical power measurement are classified as one of the types in Sections 4.2.1 and 4.2.2. 4.3 Electrical Power Analyzer Types. Electrical power analyzer types that are within the scope of this standard are the types listed in Tables 4-1 and 4-2. 4.4 Nonelectrical Power Measurements. Nonelectrical power measurements that are within the scope of this standard are as follows: 5. Requirements 5.1 Test Plan. The test plan shall be one of the following options:
7	5.2 Values to be Determined and Reported. The values to be determined and reported, if specified in the test plan in Section 5.1, shall use the units of measure listed in Table 5-1 unless otherwise specified in the test plan. 5.3 Test Requirements
9	6. Instruments 6.1 Instrument Requirements for All Measurements
10	6.2 Laboratory Electrical Measurements, Linear Loads. Electrical power measurement system accuracy for linear loads in laboratory applications shall be within ±1.0% of reading unless otherwise specified in the test plan. 6.3 Laboratory Electrical Measurements, Nonlinear Loads. Electrical power measurement system accuracy for nonlinear loads in laboratory applications shall be within ±1.0% of reading unless otherwise specified in the test plan. 6.4 Field Electrical Measurements, Linear Loads. Electrical power measurement system accuracy for linear loads in field applications shall be within ±3.0% of reading unless otherwise specified in the test plan. 6.5 Field Electrical Measurements, Nonlinear Loads. Electrical power measurement system accuracy for nonlinear loads in field applications shall be within ±3.0% of reading unless otherwise specified in the test plan. 6.6 Nonelectrical Power Measurements 7. Test Methods 7.1 Electrical Power Measurement Test Methods
12	7.2 Shaft Power Measurement Test Methods. The measurement of shaft power of rotating machines, in the absence of transients, using a dynamometer or a torque meter, shall be determined using Equation 7-1 for SI units or Equation 7-2 for I-P units.
13	7.3 Measurements of Power Derived from the First Law of Thermodynamics. This section provides an example of deriving power by applying the first law of thermodynamics.
16	7.4 Measurements of Fluid Power Output from a Pump. The measurement of fluid input power to a pump, in the absence of transients, shall be determined using Equation 7-13 for SI units or Equation 7-14 for I-P units. 8. Uncertainty Calculations 8.1 Post-Test Uncertainty Analysis. A post-test analysis of the measurement system uncertainty, performed in accordance with ASME PTC 19.1 1, shall accompany each power measurement if specified in the test plan in Section 5.1. Installation effects on…
17	8.2 Method to Express Uncertainty. All assumptions, parameters, and calculations used in estimating uncertainty shall be clearly documented prior to expressing any uncertainty values. Uncertainty shall be expressed as shown in Equation 8-1: 9. Test Report 9.1 Electrical Power Measurements Described in Section 7.1 9.2 Shaft Power Measurements Described in Section 7.2
18	9.3 Fluid Input Power Measurement to a Pump Described in Section 7.4
19	10. References
20	Informative Appendix A: Informative References and Bibliography
21	Informative Appendix B: Power Measurement Basics B1. Power Compared to Energy B2. Electrical Voltage and Current Measurement Basics B2.1 Instrumentation. Voltage and current instrumentation may be based on analog or digital technology. Digital instrumentation is the more modern of the two technologies and often has wider bandwidth, greater accuracy, and the capability to accurate… B2.2 Adequate Bandwidth. Bandwidth is defined at a gain of –3 dB, corresponding to a spectral density that is greater than half of the maximum. Therefore, with an adequate bandwidth, the gain at the frequency of what is being measured will be 0 dB…. B2.3 Range Extenders. The ranges of instrumentation may be extended through the use, for example, of resistive shunts, current transformers, Hall-effect transducers, potential transformers, or resistive dividers. The accuracy, bandwidth, and impedanc… B2.4 Harmonic-Related Losses. Harmonics is the name given to the condition where currents or voltages have frequencies that are integer multiples of the fundamental power frequency. In a normal alternating current (AC) power system, the voltage varie… B3. Electrical Power and Power Factor Measurement Basics B3.1 Power. Power is the time average of the product of the instantaneous magnitude of voltage and current for both linear and nonlinear loads. The power associated with linear AC loads may be obtained if the root- mean-square (RMS) values of voltage…
22	B3.2 Power Factor. Power factor is defined as the ratio of the true power in watts to the apparent power in volt-amperes. This is true for both linear and nonlinear loads. Power factor is a figure of merit, indicating how much of the apparent power i… B3.3 Considerations for Nonlinear Units Under Test. Nonlinear units under test (UUTs) may require appropriate isolation and precautions to ensure that accurate power measurements are obtained. Nonlinear UUTs may require the use of instrumentation tha…
23	B3.4 Connections and Loading Effects. The impedance of the voltage and current measuring elements and their loading effects may introduce errors in either the voltage or current reading, and thus the power reading. The connections required to measure… B4. Nonelectrical Power Measurements B4.1 Shaft Power Measurement. Shaft power is the product of the instantaneous shaft torque and the instantaneous shaft speed as prescribed in Section 7.2. Alternatives for measuring equipment include a noncontact speed sensor combined with an in-line… B4.2 Power Derived from the First Law of Thermodynamics. Power derived from the first law of thermodynamics, as defined in the test plan, is determined from combinations of temperature measurements, pressure measurements, flow rate measurements, and … B4.3 Fluid Power Output from a Pump. Fluid power output from a pump is the product of the volumetric flow at the pump outlet and the pressure differential across the pump as defined in the test plan.
24	Informative Appendix C: An Uncertainty Analysis Example for the Input and Output Power of a Variable-Frequency Drive C1. Review Test Objectives and Test Duration C2. List All Independent Measurement Parameters and Their Nominal Levels C3. List All Calibrations and Instrument Setups That Will Affect Each Parameter C4. Define the Functional Relationship Between Independent Parameters and the Test Result

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Standard Title	ASHRAE Standard 41.11-2023 — Standard Methods for Power Measurement (ANSI Approved)
Published Code	ASHRAE
Publication Date	2023
Pages Count	32

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ASHRAE Standard 41.11 2023

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