A UL working group focused on updating charge standards for flammable (A3) refrigerants like propane (R290) in HVAC applications such as outdoor monobloc heat pumps is aiming to finish revised text in 2027 that will be incorporated in the 2028 (fifth) edition of the UL/CSA 60335-2-40 safety standard for electrical heat pumps, air-conditioners, and dehumidifiers used in the U.S., Canada and Mexico.
Avipsa Mahapatra, Climate Campaign Director at the Washington, D.C. branch of the Environmental Investigation Agency (EIA), provided an update on the progress with A3 refrigerant standards for HVAC applications at the ATMOsphere (ATMO) America 2026 conference in Tarrytown, New York on June 2. The conference was organized by ATMOsphere, publisher of NaturalRefrigerants.com.
Last year the EIA provided its analysis on the evolving U.S. standards for hydrocarbon HVAC equipment in a report called “Enabling Ultra-low GWP Cooling and Heating: Updating U.S. Safety Standards and Codes.”
The EIA is a member of Working Group 3, which is part of the CANENA Technical Harmonization Subcommittee (THSC) 61D that oversees the UL/CSA 60335-2-40 safety standard. Text updates will specify the design and construction requirements of the use of A3 refrigerants in outdoor (indirect) monobloc heat pumps in residential applications, which employ an air-to-water design; this will include an R290 charge of up to 4.94kg. “Without these updates, no product can be certified to UL standards, and without a UL listing, it is restricted from the U.S. market,” said Mahapatra.
“The most urgent task is to ensure that safety research and testing are happening so that updates can happen to ASHRAE and UL.”
Avipsa Mahapatra, the Environmental Investigation Agency
UL currently limits the charge of propane in all residential HVAC equipment to 114g, well below what is required by most HVAC appliances. By contrast, the global IEC 60335-2-40 (seventh edition) standard, approved in 2022 after a decade of research, testing and international cooperation, allows higher amounts of R290. This includes 4.94kg in outdoor air-to-water HVAC systems and 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. The IEC standard is followed in Europe, where residential R290 air-to-water heat pumps are plentiful.
Current efforts to allow the higher charge of R290 in outdoor/indirect heat pumps in the U.S. are also 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 the charge limit for A3 refrigerants in these heat pumps to 4.94kg.
These initiatives to raise the charge level of propane are based on U.S. research demonstrating the safety of systems using the higher charge, even though some of this has happened in Europe. The Oak Ridge National Laboratory (ORNL) is involved in two such research efforts. One, funded by the U.S. Department of Energy, is assessing commercial chillers and air-to-water heat pumps, as well as packaged, direct small-charge systems. The other is a joint project (AHRTI Project 9021) with the Air-Conditioning, Heating, and Refrigeration Technology Institute (AHRTI), the research arm of the Air-Conditioning, Heating, and Refrigeration Institute (AHRI). The AHRTI Project 9021, funded by the California Air Resources Board (CARB), is evaluating R290 in indirect monobloc heat pumps.
“The most urgent task is to ensure that safety research and testing are happening so that updates can happen to ASHRAE and UL,” said Mahapatra, adding that research and testing have been “the biggest barrier” to adoption of higher propane charges in HVAC.
Feeding the 2030 code cycle
Mahapatra noted that UL and ASHRAE standard updates need to be done by the end of 2028 so that “they can feed into the 2030 code cycle” for model codes under the ICC (International Code Council) and the IAPMO (International Association of Plumbing and Mechanical Officials). The model codes are in turn followed by state and local building codes. In addition, the U.S. Environmental Protection Agency (EPA) would adopt UL/ASHRAE updates in its SNAP (Significant New Alternatives Policy) program, and states could also enact regulations in support of natural refrigerant-based HVAC applications.
“Nobody wants a patchwork of regulations, but in the absence of federal regulations and federal signals, given the global signal, we want to make sure that the industry is still going in the same direction,” she said.
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. Washington State recently held a public hearing regarding a proposal to change a state code that would provide a compliance pathway for R290 air-to-water heat pumps.
She also alluded to the need to develop market readiness for R290 HVAC systems via demonstration projects, workforce development and incentive programs. At the ATMO America 2026 conference, a panel of HVAC experts, who are helping to chart a path for natural refrigerants like CO2 (R744) and propane to be used in HVAC applications in the U.S., described their approaches.
More industry participation, please
Mahapatra stressed the need for more participation by industry stakeholders, especially OEMs that are looking to bring A3 HVAC systems to the U.S. market, in the development of new A3 HVAC charge standards. “We really don’t have enough industry representation right now working on the text changes,” she said. “Please get engaged and involved in the [UL 2-40 and ASHRAE 15.2] safety standards negotiations and discussions that are happening right now in the U.S. and North America.”
She added that standards committees have historically had representation by fluorochemical producers or users that are largely dependent on fluorochemicals, “which is why it is so important that the folks that are involved in the safety standards are people who genuinely want to modernize these standards and to allow for the [charges] to increase.”
While much of the focus of the charge increase for propane in HVAC is on monobloc air-to-water heat pumps, Mahapatra mentioned other systems likely to be approved for charge updates, assuming research is concluded in a timely manner and concludes that the changes will be safe. These include self-contained ACs and heat pumps such as heat pump water heaters, with a charge of about 150 to 300g, and commercial small-to-medium-size chillers and air-to-water heat pumps, with a charge of about 25kg.
However, these appliances would only cover 20 to 25% of the U.S. market, what Mahapatra called “partial harmonization” with the IEC 60335-2-40 standards. “But there is a way we can get to about 80 to 90 percent of the U.S. market if we are again looking at more product types and more research.” Full harmonization with IEC 60335-40 that would cover all common types of direct expansion systems, including ducted and ductless central units.
Demand for propane-based HVAC appliances is likely to grow in the coming years as the production and import of HFCs diminishes under the AIM Act and Kigali Amendment, with a drop of 70% from baseline in 2029, accompanied by a sharp rise in price. “If you are locking yourself into a system that’s going to rely on HFCs for the next 15 to 20 years, you better know where you’re getting that chemical from at a price that you can afford,” said Mahapatra.
