Did you know that a heat pump can act as both a heater and an air conditioner? This is because a heat pump uses a reversing valve. ANSI/ASHRAE 40-2025: Methods of Testing for Rating Heat-Operated Unitary Air-Conditioning and Heat Pump Equipment covers test methods for unitary air-conditioning and heat-pump equipment.
How Can a Heat Pump Heat and Cool? – The Reversing Valve
The main difference between these two HVAC systems is that a heat pump can heat and cool air, while an air conditioner cannot. The key component that allows a heat pump to switch between heating and cooling modes is the reversing valve. This valve changes the direction of the refrigerant flow. By reversing the flow of the refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa.
Why Test Air-Conditioning and Heat Pump Equipment?
Testing for rating heat-operated unitary air-conditioning and heat pump equipment is essential to assure consumers can accurately compare the energy efficiency of different models. It enables consumers to selecting more efficient units and make informed purchasing—ultimately leading to potential energy cost savings.
Established standards like ANSI/ASHRAE 40-2025, which define the testing procedures and rating scales used to determine the cooling and heating capacity of these appliances under specific conditions, are crucial for assessing energy inputs.
What Is ANSI/ASHRAE 40?
ANSI/ASHRAE 40-2025 applies to heat-operated unitary air conditioners and heat pumps consisting of one or more assemblies, including engine-driven systems. This American National 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. These test methods may be used as a basis for rating such equipment, but it is not the purpose of ANSI/ASHRAE 40-2025 to specify methods of establishing ratings.
This standard does not include methods of testing the following types of equipment:
- Heat-operated absorption and engine-driven liquid chillers not part of a unitary air conditioner or heat pump
- Electrically driven unitary air conditioners or heat pumps
- Refrigerating systems employing the Peltier effect
- Desiccant-based cooling systems
What AC and Heat Equipment Does ANSI/ASHRAE 40 Cover?
Equipment within the scope of ANSI/ASHRAE 40-2025 may be classified as follows:
- Component arrangements: Factory-assembled equipment employing heat–operated or mechanical refrigeration cycle or cycles (e.g., a packaged unit); equipment employing a heat–operated or mechanical refrigeration cycle with indoor and outdoor sections in separate assemblies (e.g., a split system); equipment employing a heat–operated or mechanical refrigeration cycle as a liquid chiller with cooling coil in separate assembly (e.g., chiller); and equipment employing refrigeration cycles and heating functions (e.g., chiller/heater)
- Method of providing air circulation through indoor section: With circulating fan incorporated with indoor assembly; and without circulating fan, for use with separate fan or air handler, or with heating equipment incorporating a fan
- Medium for heat transfer to or from the outdoors: Air; water (or brine); and evaporatively cooled condenser (cooling only)
Essentially, ANSI/ASHRAE 40-2025 establishes a standardized procedure to assess the capacity and energy efficiency of such units; this standard is used to determine the proper rating for these types of equipment based on their performance under controlled testing conditions.
ANSI/ASHRAE 40-2025: Methods of Testing for Rating Heat-Operated Unitary Air-Conditioning and Heat Pump Equipment is available on the ANSI Webstore.