The U.S. branch of the Environmental Investigation Agency (EIA) said in a new report that it supports full harmonization of U.S. standards on the use of flammable (A3) hydrocarbon refrigerants in HVAC equipment with the global standard IEC 60335-2-40.
This could enable 78–88% of new air-conditioning and heat-pump equipment in the U.S. to transition to propane (R290) between 2030 and 2035, according to the EIA.
The EIA provided its analysis on the evolving U.S. standards for hydrocarbon HVAC equipment in the report, called “Enabling Ultra-low GWP Cooling and Heating: Updating U.S. Safety Standards and Codes.” It includes an analysis of R290 charge size requirements in the U.S. market by Daniel Colbourne, Co-Owner of Re-Phridge, a U.K. consultancy.
Full harmonization with IEC 60335-2-40 on the use of A3 refrigerants in HVAC would go well beyond what is currently underway in the U.S., which the EIA called “partial harmonization.” In its report the EIA pointed out that so far the partial harmonization proposals and research considering expanded A3 charge sizes leave the “majority of current system types not yet addressed or considered,” notably residential ducted systems, mini-split ACs and commercial packaged and rooftop units.
The latest version (edition 7) of IEC 60335-2-40 was approved in 2022 after a decade of research, testing and international cooperation. It allows up to 988g of R290 in HVAC units located indoors or connected to the indoor space, such as ductless split ACs or ducted central systems; these are subject to room size limits and other equipment design requirements. It also allows 4.94kg of R290 in outdoor/indirect systems such as air-to-water monobloc heat pumps, among other limits.
While Europe and other regions have fully harmonized with the global IEC standard, in the U.S., standards bodies have taken a more limited approach, enabling greater use of A2L (lower flammability) refrigerants but not A3s. For example, UL’s most recent (fourth) edition of the 60335-2-40 standard limits the use of R290 to 114g for all HVAC residential and light-commercial applications. The ASHRAE-15 standard also significantly restricts A3 refrigerant use in residential and commercial applications to less than 150g with any larger amount requiring a approval by a local jurisdiction’s code officials.
“This approach has the benefit of bringing the U.S. market into alignment with the vast majority of other regions that follow and utilize the IEC standard.”
EIA report
Current efforts to support greater use of R290 in outdoor/indirect heat pumps in the U.S. – the partial harmonization scenario – are being made by ASHRAE under its 15.2-2022 Safety Standard for Refrigeration Systems in Residential Applications. The 15.2 subcommittee overseeing this standard has proposed an amendment to increase in the charge limit for A3 refrigerants in these heat pumps to 4.9kg. U.S. Department of Energy (DOE) funding for research on the risks involved in making that change has been delayed, but California announced that it will be providing funding.
Two other research and testing projects on A3 refrigerant safety are underway at Oak Ridge National Laboratory (ORNL). One project looks at self-contained heat pump and air-conditioning equipment including window ACs and heat pump water heaters; the IEC limit for these units (without mitigation) is 152g, while the current UL limit is 114g. A second project examines small- to medium-size commercial chillers.
The UL recently announced formation of a Technical Harmonization Committee (THC), which will begin meeting in October 2025 to develop the fifth edition of UL 60335-2-40. “This committee is expected to consider proposals on a range of topics related to equipment safety, including requirements related to flammable refrigerants,” said the EIA report.
Aligning the U.S. with other regions
The EIA report called for a full harmonization with IEC 60335-40 that would cover all common types of direct expansion systems, including ducted and ductless central units, up to the 988g maximum charge limit as well as indirect systems up to 4.94kg. “This approach has the benefit of bringing the U.S. market into alignment with the vast majority of other regions that follow and utilize the IEC standard,” the report said, acknowledging that this would require additional resources be directed to risk assessment and research on additional scenarios and equipment types.
The EIA also invites U.S. standards bodies to go “beyond IEC 60335-2-40” by considering HVAC systems with up to 1.5kg of A3 refrigerants thereby addressing “nearly all common residential and commercial [air-conditioning and heat pump] applications in the U.S. market and around the globe.”
The EIA noted that if U.S. safety standards only partially harmonize with the IEC by addressing indirect systems, a widespread transition to A3s would mean the U.S. would need to replace existing central HVAC with new system architectures such as air-to-water and hydronic systems where the A3 refrigerant can be contained outdoors and only water or a secondary heat transfer fluid enters the building. Even under full IEC harmonization, to enable R290 in the remaining 10–20% of equipment would either necessitate these systems designed as indirect systems or require further updates to safety standards, the EIA said.
The report called full harmonization with IEC 60335-2-40 “a realistic path to enable a vast majority of newly manufactured U.S. air conditioners and heat pumps to use R290 and other ultra-low GWP A3 refrigerants nationwide.” But, at minimum, U.S. standards “should advance near-term proposals to enable A3s in self-contained and indirect system types.” UL and ASHRAE standards are typically adopted by the U.S. Environmental Protection Agency’s SNAP (Significant New Alternatives Policy) program and by model codes – notably the International Mechanical Code and Uniform Mechanical Code – which are followed by state and local codes.
The EIA in its report urges all interested stakeholders to engage with discussions in UL and ASHRAE standards committees and to support additional safety research and testing that would enable a “full harmonization” or “beyond IEC” scenario to be fully vetted. “If safety research and proposals to fully harmonize with IEC cannot be finalized by the 2027 deadline for inclusion in 2030 model codes, this work should be continued and finalized as soon as possible for inclusion in 2030 code proposals for 2033 model codes,” the EIA said.
States accelerating adoption
More than 20 U.S. states have passed legislation that effectively accelerates adoption of UL and ASHRAE standards into state codes before they are incorporated into model codes. The laws stipulate that existing model codes should not prevent the use of refrigerants approved under nationally recognized safety standards and under the EPA’s SNAP program. “This approach was taken to support timely adoption of A2L refrigerants and can provide a similar near-term solution for allowing market adoption of equipment using A3 refrigerants while state and local codes are still in the process of being updated,” noted the EIA’s report.
In May, New Yorkers for Cool Refrigerant Management, a regional grassroots group aimed at reducing fluorinated refrigerant emissions, wrote a letter urging the New York State Building Code Council to allow higher but safe levels of A3 refrigerants in monobloc heat pumps and other HVAC equipment when those levels are approved by ASHRAE and UL. New York is one of the states that allows early adoption of UL and ASHRAE standards into state codes.
