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ASHRAE Standard 40-2025 -- Methods of Testing for Rating Heat-Operated Unitary Air-Conditioning and Heat-Pump Equipment (ANSI Approved), 2025
- ASHRAE Online Bookstore
- Addenda
- Errata
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- ANSI/ASHRAE Standard 40-2025 [Go to Page]
- Contents
- Foreword
- 1. Purpose [Go to Page]
- 1.1 This standard provides test methods for determining the heating and cooling output capacities and energy inputs of unitary air-conditioning and heat-pump equipment that is heat-operated (see Section 3, “Definitions”).
- 1.2 These test methods may be used as a basis for rating such equipment, but it is not the purpose of this standard to specify methods of establishing ratings.
- 2. Scope [Go to Page]
- 2.1 This standard applies to heat-operated unitary air conditioners and heat pumps consisting of one or more assemblies, including engine-driven systems. Where such equipment is provided in more than one assembly, the separate assemblies are designed...
- 2.2 Equipment within the scope of this standard may be classified as follows:
- 2.3 This standard does not include methods of testing the following types of equipment:
- 3. Definitions and Symbols
- 4. Classifications [Go to Page]
- 4.1 Heat-operated unitary air-conditioning and heat-pump equipment within the scope of this standard is classified as follows.
- 4.2 This Standard Does not Include Methods of Testing the Following Types of Equipment
- 5. Instruments and Measurements [Go to Page]
- 5.1 Instruments and data acquisition systems shall be selected to meet the measurement system accuracy specified in this section.
- 5.2 Measurements from the instruments shall be traceable to primary or secondary standards calibrated by the National Institute of Standards and Technology (NIST) or to the Bureau International des Poids et Mesures (BIPM) if a National Metrology Inst...
- 5.3 Instruments shall be applied and used in accordance with the following standards:
- 5.4 Instrument Accuracy Requirements and Measurement Methods. Measuring instruments shall be selected to meet or exceed the instrument accuracy or measurement uncertainty listed in Table 5-1 for each type of measurement. Instruments and measurement m...
- 5.5 Fluid Properties
- 5.6 Fuel Higher Heating Values. Apply ASHRAE Standard 41.1310 to obtain the higher heating value for fuels, including natural gas, commercial propane, manufactured gas, and bioderived gas.
- 5.7 Air-Sampling Tree Requirements. An example of an air-sampling tree is shown in Figure 5-1. The air- sampling tree shall be constructed of plastic, stainless steel, or other rigid materials. The air-sampling tree shall have a main flow trunk tube ...
- 5.8 Aspirating Psychrometer Requirements. The inlet of the aspirating psychrometer is connected to the air-sampling-tree outlet. The aspirating psychrometer consists of a flow section and a fan to draw air through the flow section and instruments to ...
- 5.9 Static Pressure Taps. Static pressure taps shall be constructed as defined in Figure 5-3 and shall be located around the duct perimeter in a measurement plane with (a) one pressure tap located on each surface of a rectangular duct and centered wi...
- 5.10 Piezometer Ring
- 5.11 Equivalent Diameter. The UUT ducts are either round or rectangular. For round ducts, the equivalent diameter DE is equal to the interior diameter D. For rectangular ducts with interior width and height dimensions equal to a and b, respectively, ...
- 5.12 Enthalpy and Pressure Measurement Apparatus. Example configurations for the test apparatus are provided below. In all cases, a means for determining the dry-bulb temperature and water vapor content of the air entering and leaving the unit and fo...
- 5.13 Cyclic Damper (Optional)
- 5.14 Units with a Fan Downstream of the Indoor Coil and a Single Outlet
- 5.15 Units without a Fan or with a Fan Upstream of the Indoor Coil and a Single Outlet
- 5.16 Units with Fans and Multiple Outlets or Multievaporators
- 5.17 Nonducted Units
- 5.18 Multisplit Units
- 6. Test Facility Arrangements [Go to Page]
- 6.1 Test Facility Arrangements. The test facility arrangements shown in Figures 6-1 through 6-8 illustrate potential testing configurations and do not represent specific requirements for all types of equipment.
- 7. Methods of Testing and Calculations [Go to Page]
- 7.1 Standard Test Methods. The following three test methods for measuring space conditioning capacity are covered in this standard:
- 7.2 Applicability of Test Methods
- 7.3 Indoor Air Enthalpy Method
- 7.4 Liquid Coil Method
- 7.5 Refrigerant Enthalpy Method
- 7.6 Airflow Rate Measurement
- 7.7 Cooling Condensate Measurement
- 8. Test Preparation and Performance [Go to Page]
- 8.1 Test Room Requirements
- 8.2 Equipment Installation
- 8.3 Airflow Measurements
- 8.4 External Pressure Measurement
- 8.5 Temperature Measurement
- 8.6 Measured Energy Input Parameters
- 8.7 Test Operating Procedure
- 8.8 Test Operating Procedure for Heating Capacity Tests
- 9. Data to Be Recorded [Go to Page]
- 9.1 Table 9-1 shows the data to be recorded during a test. Items indicated by an “x” under the test method columns are required when that test method is employed.
- 9.2 Test Tolerances
- 10. Test Results [Go to Page]
- 10.1 Capacity Test Requirements
- 11. Symbols Used in Equations
- 12. Reference Properties and Data [Go to Page]
- 12.1 Thermodynamic Properties of Dry and Moist Air. The thermodynamic properties of dry and moist air shall be obtained from ASHRAE Research Project RP-1485.11
- 12.2 Thermodynamic Properties of Liquids. The thermodynamic properties of liquids shall be obtained from NIST Standard Reference Database 23 (REFPROP)12 or from the source of the liquid and shall be recorded in the test report.
- 12.3 Thermodynamic Properties of Refrigerants. The thermodynamic properties of refrigerants shall be obtained from NIST Standard Reference Database 23 (REFPROP)12 or from the source of the refrigerant and shall be recorded in the test report.
- 13. References
- Normative Appendix A: Environmental Chamber Design Considerations for Testing Heat-Actuated Cooling Equipment [Go to Page]
- A1. General Observations
- A2. Chamber Conditions Uniformity
- A3. Test Equipment Handling [Go to Page]
- A3.1 Design Chambers with High Ceilings. Generally, chambers are built from modular standard panels and come with standard 1.75 m or 2.5 m (6 ft or 8 ft) ceilings. At least a 3 m (10 ft) ceiling is recommended. This feature will greatly facilitate in...
- A3.2 Design the Chamber(s) with a Floor that Will Allow One to Move in Heavy (up to 450 kg [1000 lb]) Test Units. The chamber floors should be able to support a load brought into the chamber with a forklift truck. Ideally, the roof should have an acc...
- A4. Refrigerant Consideration
- A5. Combustion and Makeup Air Considerations
- A6. Combustion Vent Products Considerations
- A7. Environmental Chamber Control Systems
- A8. Safety Controls [Go to Page]
