If there is to be a next generation of refrigerants in stationary equipment beyond hydrofluorocarbons (HFCs), it appears they will be hydrofluoroolefins (HFOs). And if that transition is to take place in the United States, it could be because of regulations or better energy efficiencies - or both.

Three red flags on this topic include:

• The beginning of production of automotive air conditioning in Europe using HFO-1234yf rather than HFC-134a.

• An announcement from the United States Environmental Protection Agency that it has given “final approval for a new refrigerant (HFO-1234yf) to be used in motor vehicle air conditioning.”

• And the ongoing research by refrigerant manufacturers and academia into the possibility of using HFOs in stationary applications.


As noted byThe NEWScolumnist John Tomczyk in the textbook he co-authored titledRefrigeration and Air Conditioning Technology, HFCs arose as a result of ozone-depleting issues with hydrochlorofluorocarbons (HCFCs).

“HFC molecules contain no chlorine atoms and will not deplete the Earth’s protective ozone layer. HFCs contain hydrogen, fluorine, and carbon atoms. HFCs do have small global warming potential,” he wrote.

But it was that GWP that first raised concern in Europe, especially with HFC-134a with a GWP of 1,430. That was considered way too high in Europe, especially with automotive air conditioning which is a vast market often with less than leak tight equipment. The issue was so potent in Europe that DuPont and Honeywell entered into a joint research project for the automotive sector that produced R-1234yf with a GWP of just 4.

The European mandate regarding HFOs in automotive stipulated a phase in for model years through 2017.

But the embracing of HFOs in automotive appears to be reaching the United States as well. According to a web publication Green Energy News, “General Motors recently announced it will be using HFO for the standard refrigerant. Beginning in 2013, the new refrigerant will be used in Chevrolet, Buick, GMC, and Cadillac models sold in the U.S.”


Aside from HVACR contractors who might do some auto or truck air conditioning service on the side, the main question to be asked concerns possible applications for HFOs in stationary units.

The topic dominated this past summer’s Refrigeration and Air Conditioning Conference at Purdue University, where both manufacturers and academia revealed efforts to make HFOs work in stationary equipment.

Here are some of the highlights of those papers (the quotes coming directly from the published papers):

• “The question arising given the success in automotive is whether HFO-1234yf can be used in other applications where R-134a is currently employed. Test results from beverage coolers optimized for R-134a, HFO-1234yf, and CO2 demonstrate that coolers can be designed for HFO-1234yf that demonstrate similar energy efficiency and cooling capacity compared to R-134a. Only minor modifications were required to achieve equivalent performance.” (DuPont)

• “In general, the thermo physical properties of R-1234yf are very similar to those of R-134a, and not as similar to those of R-410A. (Sample heat exchangers) simulations have shown that R-134a and R-1234yf have similar results for outlet refrigerant temperature and heat load. However, the pressure drop does vary and changes to the heat exchanger design and piping in these systems may be required.” (University of Maryland)

• “We have evaluated the performance of room air conditioners using HFO-1234yf. To meet the properties of (that refrigerant), we modified a room air conditioner that had been using R-410A. Equalizing the refrigerant distribution of paths is then required. The increase in the diameter of the gas-side connecting pipe involves challenges such as increasing the workload of the installation.” (Hitachi)

• “At the present stage, it seems that mixtures of HFO-1234ze(E) and HFC-32 are strong candidates for replacing HFC-410A in domestic heat pumps.” (Kyushu University in Japan)

• HFO-1234yf “has potential in applications such as small commercial and residential refrigeration systems and other areas where a medium pressure refrigerant can be efficiently employed and where low global warming refrigerants are needed or desired.” (Honeywell)


That lower GWP is driving attention to HFOs.

“HFO refrigerants offer potential safe and energy efficient solutions to many of the existing refrigerants which are also potent greenhouse gases,” said Jeff Moe, director of global policy and advocacy at the Ingersoll Rand Center for Energy Efficiency and Sustainability. “Given the global pressure on greenhouse gases, we need to continuously look for alternatives that minimize environmental impact.”

For Honeywell, HFOs “are the next evolution for the ACR industry,” said David Diggs, global business director for refrigerants. “They are safe, and they mimic energy efficiency and capacity of HFCs.”

Eric Youngdale, global market manager for DuPont Refrigerants, said, “The low GWP of HFO-1234yf makes it a promising reduced GWP option, either as a single refrigerant or in blends, to the current HFCs in stationary applications.” He noted, for example, that the Air-Condition, Heating, and Refrigerating Institute (AHRI) “recently announced an industry wide cooperative research program to evaluate low GWP refrigerants including HFOs.”

Industry observer Jay Kestenbaum, who is senior vice president for product management at Airgas which distributes a wide range of refrigerants, said HFOs “are currently the generally accepted direction for long-term refrigerant replacement with low GWP factors.”

At the same time, Brett Fraser, Arkema global business manager for refrigerant blends, said he sees HFOs “as alternatives in several, but not all, current HFCs market sectors.” This would relate, he said, to situations where there might be equal efficiencies but HFCs prove less costly than HFOs. “Arkema believes that long term HFOs may be used in some market sectors but others may continue using HFCs, such as meter dose inhalers. All (HFC) refrigerants currently listed will probably be used, specific to a given market sector.”


With all the potential HFOs might have in stationary, it appears they will make inroads in the United States primarily through a mandated phase down of HFCs (which currently is not anticipated in Congress). But all this could also tie in with energy efficiencies.

“Like most changes, it takes government regulations or financial incentives to make it happen,” said Ken Bodwell, a contractor with Innovative Service Solutions. “If the automotive manufacturers can cost justify - and the impact to buyers is reasonable - then the conversion to 1234yf may be successful (in stationary).”

Honeywell’s Diggs said, “In Europe environmental sensitivity is driving change and regulation, while the United States is using regulations to try to keep pace.”

Youngdale of DuPont said, “The future of government regulations for the use of HFCs is uncertain at this time. That being said, it is apparent that there is a growing awareness and interest by many HVACR equipment owners and specifiers in exploring technology options with lower carbon footprint.”

“The significant majority of users in the United States will not switch unless they have to or there are significant economic benefits,” said Airgas’ Kestenbaum.

For Arkema’s Fraser, “The key drivers for use of HFOs in the future should be the energy efficiency in their applications. In refrigeration applications, the energy consumption is far more significant an issue than the direct emissions of the refrigerant.”


The specific acceptance of HFOs will be driven by cost and an issue related to the safety rating of the refrigerants.

Any new refrigerant carries a premium cost which eventually comes down as such a refrigerant goes into wider use - and/or the cost of being phased out refrigerant rises.

Bodwell expresses a frustration in this regard. “The majority of end users are tiring of the increasing costs associated with change.”

Kestenbaum said, “Our information is that the anticipated price will be several times the cost of the current HFCs which will probably mean a slower than optimal transition similar to the original changes from R-22 to R-410A or even CFC-12 to R-134a in the early years.”

Even as the cost consideration plays itself out, there is still the issue of the safety rating.

Whereas CFCs, HCFCs, and HFCs all garnered A1 safety ratings, and HC refrigerants typically have A3 safety ratings because of flammability issues, HFOs have earned a first of its kind A2L safety rating from the American Society of Heating Refrigerating and Air conditioning Engineers (ASHRAE) because of what research has determined to be a very low flammable potential.

Here those contacted had varying thoughts.

DuPont’s Youngdale said the A2L classification acknowledges “the reduced flammability properties of refrigerants such as 1234yf as compared to other current class 2 and class 3 refrigerants.” Applications of HFOs will depend, he said, on “codes and standards that apply to the given application, such as ASHRAE Standard 15 and Underwriters Laboratories standards or similar international safety standards.”

Arkema’s Fraser said, “Some governments will find the low flammability an acceptable risk. Others will not.”

Moving from A1 to A2L refrigerants “is not viewed as a huge leap as it is being done successfully in mobile air conditioning,” said Honeywell’s Diggs. He did note there would be a learning curve. To which he said, “Honeywell customers will be well informed about how to use these new products.”

Said IR’s Moe, “Any elevation in flammability must be evaluated for safety in each application. The best way to do this is through industry participation in testing and code modification to ensure responsible use of these fluids.”

Kestenbaum pointed to the OEMs for assurances regarding the refrigerant. “The issues of safety ratings will have to be addressed by the manufacturers who not only have the industry safety obligation but also have their own commitment to supply products formulated for a reasonably safe approach for which the various products are intended.”

There have not been many announcements from OEMs concerning stationary products using HFOs. In early 2011, Klima Therm and Cool-Therm initially reported of plans to use the HFO-1234ze in its oil-free, magnetic bearing centrifugal compressors - but then retracted a bit. A spokesman for the companies said on Feb. 11, “We believe that HFO refrigerants show great promise for the future and could meet the pressure need for an in-kind, low GWP alternative to HFC refrigerants. However, following discussions with Geoclima S.r.l. and Danfoss Turbocor, we accept that further development work and testing are required before these products can be introduced to the market. We will continue our research and development activities with these new refrigerants and plan to offer an HFO-based Turbomizer chiller to the market when it is fully qualified through our supply chain.”

Fraser of Arkema said, “Contractors and customers will be cautious in North America. Demonstration of safe use will contribute to alleviating that concern, but any incidents will adversely impact acceptance of A2L alternatives.”

Bodwell indicated contractors could embrace an A2L refrigerant. “I do not have an issue with the A2L safety rating. Although (HFOs) can ignite, it takes a lot. Various studies have it at 800 to 900°C. In stationary applications, education of the users will be required and specific applications may be excluded. But from what I’ve read, HFO-1234yf appears to be as safe as R-134a.”

Sidebar: It Is Only Natural

One of the most interesting aspects of HFOs coming to the stationary market is increased potential for so-called “natural” refrigerants such as ammonia, propane, and isobutene to make stronger inroads, in part by leveraging the fact that the industry’s willingness to embrace the new A2L safety rating may open the door to more acceptance of other refrigerants beyond the A1 classification.

Jeff Shapiro of the International Code Consultants implied as much at the March 2011 conference of the International Institute of Ammonia Refrigeration. He told an audience of more than 1,000 engineers and contractors that Underwriters Laboratory “is preparing for an influx of HC refrigerants in packaged equipment coming to the U.S.” In noting the flammability issue of HCs, he suggested that might open the door for a broader use of ammonia, which has a toxicity issue.

Stan Fraser of Arkema, a manufacturer of HFC refrigerants, indicated the same. “It is unclear whether North American systems will be redesigned to accommodate the additional risk (of a non-A1 refrigerant), but one company has applied for domestic refrigerator SNAP approval for hydrocarbons.”

As noted by Shapiro, the natural refrigerants sector has been gaining its own inroads, as has been reported on in past issues ofThe NEWS, as the example of the efforts of ComStar International, which markets HFCs, to allow for wider use of the HC-441a.

So while HFOs might become the next generation of refrigerants for stationary HVACR equipment, there could be a next, next generation of natural refrigerants in the United States running very close behind - if not running parallel to - HFOs.

Publication date:05/23/2011