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For several years, the regulatory landscape concerning refrigerants used in air conditioning and refrigeration equipment has been in flux, but that is now changing. Not only have certain states recently mandated the phasedown of some HFCs, but last December, Congress passed the American Innovation in Manufacturing (AIM) Act, which gives the Environmental Protection Agency (EPA) the authority to phase down the consumption and production of HFC refrigerants and establish sector-based limits. While the details have not yet been finalized, the general approach for the limits are consistent with the Kigali amendment, which calls for an 85% phasedown of HFC production and consumption over a 16-year timeframe. EPA has until October to issue regulations that detail how it will administer the phasedown.

Chiller OEMs have been preparing for this phasedown for years, and they have been working to identify alternative refrigerants that not only comply with these new laws but are also efficient, safe, and cost-effective.

Regulatory Actions

The passage of the AIM Act has signaled that the U.S. intends to reengage with international efforts to reduce greenhouse gases and will require that the U.S. catch up with the international efforts, which began several years ago, said Brian Smith, director of chiller products at Johnson Controls. That said, he added that headwinds around low-GWP, equipment safety standards, building codes, flammability, availability, cost, and performance may temper the rate at which the shift occurs.

“While this affects the entire sector, it is significant to direct air conditioning systems such as packaged rooftops and VRF, as well as small scroll chillers, where the only [low-GWP] options today are mildly flammable refrigerants,” he said. “As a prerequisite to the use of these new mildly flammable (A2L) options, equipment safety standards and building codes must be updated for use in direct systems to accommodate the larger charge volumes needed for proper operation. While much work has been done in this arena, individual states and provinces adopt and update their codes at different intervals. There is no nationwide edict to do this uniformly, and the different adoption rates could ultimately lead to different effective dates with the U.S. and Canada.”

Revising codes and standards can be a complex and lengthy process as well. For example, to transition chillers from R-410A to new lower flammability A2L refrigerants will require updates to safety standards like UL 60335-2-40 and ASHRAE 15, as well as adoption by the IMC, UMC, IFC, and NFPA1 model building codes, and then adoption by the states, said Gaurang Pandya, president of Carrier Commercial HVAC. The UL 60335-2-40 and ASHRAE 15 standards have been updated for A2L refrigerants, but the model code updates have not been completed, although the 2024 update process is now underway.

Another challenge is that many individual states are already adopting or proposing their own regulations to phase down high-GWP refrigerants. “Eight states have adopted the old vacated EPA SNAP [Significant New Alternatives Policy] Rule 21 to phase out R-134a and R-410A for use in chillers, and 10 other states are in the process of adopting the regulation with an effective date of Jan. 1, 2024,” said Pandya.

California is one of the states that is well along in the process of adopting regulations to phase down the use of high-GWP refrigerants, but it has gone a step further by proposing a GWP limit of 750 for chillers starting in 2024 (the same GWP limit will be required for ducted residential and commercial air conditioning equipment by 2025 and in VRF systems by 2026). Other states are implementing SNAP Rules 20 and 21, which prohibit the use of certain HFCs, but have not yet prescribed GWP limits, said Victor Marinich, global segment marketing director of air conditioning at Danfoss.

“The recent passage of the AIM Act has complicated things a bit, at least in the near term,” he said. “Danfoss expects states to drop their HFC regulations and fall in line with the EPA’s AIM Act implementation, which is likely to resemble California’s approach. Therefore, we will likely have a de facto unified national HFC phasedown for air conditioning chillers, with 49 states using the EPA’s phasedown and California using its own.”

While the industry waits to see what EPA’s final regulations will look like, under the AIM Act schedule, there will be a 10% reduction in the weighted use of HFCs starting in 2022; then in 2024, there will be a 40% reduction, said Jim Macosko, general manager of Daikin Applied.

“As part of the effort to achieve this 40% reduction, it is likely the EPA will reinstate SNAP Rule 21, which delisted R-134a and R-410A as an approved refrigerant for new chiller use beginning Jan. 1, 2024. The court had invalidated that rule, but with the AIM Act in place, it may be revisited and reestablished,” he said. “This means producers of refrigerants such as R-410A and R-134a will be limited in the amount of HFCs they can sell, which will also limit supply and, due to relatively high demand, increase prices.”

Chiller Options

In response to regulatory actions that will phase down the production of high-GWP refrigerants such as R-410A and R-134a, OEMs are researching a variety of different low-GWP options. Daikin Applied, for example, is currently testing alternatives across its centrifugal, screw, and scroll compressor portfolio and has plans to introduce R-1233zd(E) and R-513A options later this year.

CONTINUAL RESEARCH: Johnson Controls is continually researching and testing new fluids, because the factors that drive this choice continue to evolve. (Courtesy of Johnson Controls)

“R-513A is viewed as an interim alternative for R-134a, with a slightly lower GWP of 629 but also lower efficiency,” said Macosko. “Longer term, R-1234ze(E) and R-515B will be the positive pressure low-GWP alternative refrigerants to R-134a in centrifugal and screw compressors.”

He added that the most efficient alternative to R-134a is R-1234ze(E), which offers the lowest GWP of 1; however, it’s a mildly flammable A2L refrigerant. R-515B, in comparison, has a higher GWP of 292 but is composed of 91% R-1234ze(E), so it has the classification of A1. Equipment designed for R-1234ze(E) can use R-515B as a nonflammable option, he said.

“For low-pressure centrifugal chillers, R-1233zd(E) is an A1 HFO refrigerant with a GWP of 1 and high efficiency. This refrigerant will also be used in other industries, driving a global supply and competitive pricing,” said Macosko.

According to Smith, Johnson Controls is continually researching and testing new fluids, because the factors that drive this choice continue to evolve.

“We are looking for optimal candidates based on a few factors: efficiency standards driving higher equipment safety standards; building codes evolving to address A2L fluids; application requirements changing for hotter climates; and evolving heat pumps and free cooling.”

The adoption of R-1233zd(E) by several centrifugal chiller manufacturers had led it to becoming one of the leading choices for part of the chiller sector, said Smith, while R-513A has been adopted as a near drop-in choice for R-134a alternatives. R-1234ze(E) has gained favor in Europe but has yet to gain traction in the U.S., as the industry wrestles with the requirements for using mildly flammable A2L fluids.

RIGHT REFRIGERANT: In North America, Carrier offers low-GWP refrigerants on a variety of chillers. (Courtesy of Carrier)

In North America, Carrier offers low-GWP refrigerants on a variety of chillers, although the company is always looking to the future to provide the right refrigerant at the right time, said Pandya. Currently, Carrier offers R-513A on its AquaEdge® 19XR centrifugal chiller and the ultra-low GWP R-1233zd(E) (1.34 GWP) on its AquaEdge 19DV centrifugal chiller.

“When considering a lower-GWP refrigerant, customers need to look at more than the refrigerant. It’s important to evaluate the chiller system as a whole,” said Pandya. “For example, Carrier’s AquaEdge 19DV centrifugal chiller was designed from the ground up to use ultra-low GWP R-1233zd(E). This allowed the system designers to optimize performance around the refrigerant, extracting as much energy efficiency as possible from the machine while also enabling a much wider operating envelope than typically seen in chillers of this type.”

Danfoss has been supporting the European transition to low-GWP refrigerants for the past several years through its full range of compressors, heat exchangers, valves, and controls. Its focus has been on R-32 and R-454B for the scroll chiller range, as both refrigerants have GWP levels below 750.

“For R-410A and R-454B, Danfoss DSH scrolls are a fixed-speed offering that use intermediate discharge valve (IDV) technology to guarantee superior part-load performance — and because these scrolls are approved for both refrigerants, chillers using R-410A today will not need to change compressors when the transition to R-454B comes,” said Marinich. “For higher efficiency chillers, Danfoss’s VZH range of variable-speed scrolls also supports R-410A and R-454B. Danfoss’s DSF range of scrolls, which also incorporates IDV technology, is dedicated for R-32 use, and we are in the process of developing a variable-speed range for R-32.”

Danfoss Turbocor® oil-free compressors support the transition away from R-134a in larger systems by offering compressors for R-513A, R-1234ze(E), and R-515B. Danfoss microchannel heat exchangers (MCHE) and brazed plate heat exchangers not only support new, low-GWP refrigerants, but are engineered to allow a chiller to be designed with a lower refrigerant charge, which is becoming more important as the industry moves toward mildly flammable (A2L) refrigerants.

The Retrofit Question

With the growing number of low-GWP refrigerant options for chillers, the question becomes whether or not these alternatives can be retrofitted into existing equipment. It is important to note that retrofitting a chiller with a new refrigerant should not be done without first consulting the chiller manufacturer, said Marinich, but generally speaking, retrofitting is not possible because many of the low-GWP refrigerants are mildly flammable.

“Further, there is no need to change out a chiller because of new refrigerant regulations alone,” he said. “Owners should also consider, for example, the unit’s efficiency, any changes to the load over time, and the age of the equipment. Replacing an older chiller with a newer one, in most cases, would provide significant savings on utility cost, provide increased reliability, and reduce the environmental impact via decreased indirect emissions in electric utilities.”

Retrofitting is a tricky topic because at a very basic level the answer is yes, said Smith; however, the difficulty varies significantly from relatively minor changes with minimal impact to operational efficiency or capacity, to major changes that significantly impact performance, operating cost, major equipment modification, plant room changes for safety, among other factors.

“We suggest the age-old advice of ‘if it isn’t broken, don’t fix it,’” he said. “Equipment is designed to contain the refrigerant and is optimized for a given fluid. The benefits of retrofits are more often related to retrofitting an existing chiller with a newer compressor and motor driveline than the refrigerant itself (especially as compressor and motor technology has improved, offering operating cost savings and a good payback). R-410A and R-134a will continue to be the refrigerants of choice versus their alternatives unless something affects their availability and price, but that will continue to evolve as time passes.”

Macosko added that even if it’s physically possible, in most cases it will not be cost effective to retrofit older chillers with new refrigerants.

“Generally, it will make more sense to maintain the equipment, minimize refrigerant loss, and keep operating with the installed refrigerant. As we have seen from the CFC and HCFC phaseout, there should be enough reclaimed refrigerant for servicing needs. And remember, the HFC reduction is a phasedown, not a phaseout. There is a 15% production tail left in 2036 for the U.S. under the Kigali amendment.”

While the HVACR industry now knows the direction of the HFC phasedown, there is still some uncertainty over what the final regulations will look like. Building owners may be confused about the various refrigerant options available and will be looking to their contractors to help them make the decision over which one to choose. For now, the best approach is for contractors to help their commercial customers research the options and choose the best equipment and system for their building application needs, said Smith.

“Refrigerants are just one component in a larger system, and the net result of cooling, heating, first cost, operating cost, and total cost of ownership are the key factors that should influence decision-making,” he said. “There are no restrictions on the fluids today, nor is there anything that will likely impact the cost or availability significantly over the life of the equipment. While there is a coming phasedown of HFCs, this is not like ozone depletion where those fluids were marked for a complete phaseout of production. Even with the AIM Act, Kigali amendment, and state level actions, the continued use of HFCs will still be allowed.”