The Daimler decision to halt conversion to R-1234yf—the low-global-warming-potential (GWP) but mildly flammable air-conditioning refrigerant—has led to a vigorous defense of the product’s safety by the joint-venture suppliers, Honeywell and DuPont. So the question becomes, “Where does the industry go from here?”
The first step is a review and possible expansion of the existing refrigerant-use risk assessments by an SAE Cooperative Research Program (CRP) of 13 OEM members, which is under way. No new testing has been announced.
German carmakers, Volkswagen in particular, had urged the close look at the Daimler data. But only Daimler actually faced a regulatory issue with the European Commission. Daimler's decision to stop R-1234yf installations and retrofit cars already using the refrigerant back to R-134a reflected the manufacturer’s concern. Other (non-German) carmakers selling in Europe have made limited installations of R-1234yf.
Avoiding the changeover encounters two regulatory roadblocks. One is the European Commission (EC) decision to begin enforcement of a mandated R-134a phase-out for “new type” vehicles as of January 1, 2013. It had held off for two years because of production delays from a new plant in China. A second is the U.S. EPA’s substantial credit for a low GWP refrigerant toward Corporate Average Fuel Economy (CAFE), although there is no mandate. R-1234yf has a global warming number of 4.0; R-134a is rated at 1430. These numbers are based on GWP multiples of carbon dioxide, which is 1.0.
General Motors is the only U.S. maker currently installing R-1234yf, and to date only in Cadillac XTS and ATS. The Honda Fit electric vehicle also is equipped. A top Ford engineering executive told AEI the company had not identified a safety issue with the refrigerant, was comfortable with the SAE studies and its own, and would deploy R-1234yf at an appropriate time. R-1234yf systems have added cost over R-134a, for the refrigerant and modified components.
Limited test data is public
Only limited data has been released publicly on the Daimler test. It reportedly simulated a head-on collision, following a drive cycle in a small car, that got turbocharger and exhaust surfaces very hot. At some point the radiator fan had been turned off, simulating a fan failure and further raising of turbo/exhaust temperatures. A modified refrigerant line permitted engineers to simulate a puncture that allowed R-1234yf to be sprayed onto the turbo/exhaust. The R-1234yf, reportedly mixed with some oil, produced a refrigerant flame.
Daimler called the test a “real world” scenario, and cited formation during the flame of hydrogen fluoride (HF), which etched the windshield milky white. HF, a toxic, corrosive gas that can result from decomposition of fluorine-content gas, was evaluated in the CRP studies, and potential exposure was considered similar to or below other fire-related exposures more frequently encountered. Further, Honeywell noted, HF is malodorous and so people would avoid a major exposure. Virtually all underhood fluids, the company added, are measurably more flammable. R-12, the nonflammable refrigerant replaced by R-134a to protect the ozone layer, would produce poisonous phosgene gas if exposed to flame.
DuPont and Honeywell said tests similar to the Daimler one were done in risk assessments performed by laboratories working for SAE CRPs. Honeywell additionally has shown tests it performed at 600°C (1112°F), which it said was the highest it encountered in an engine compartment, and the refrigerant did not burn.
The CRP assessments concluded the refrigerant was safe, in the same risk category as riding in an elevator. Need for safe routing of refrigerant lines was covered in ISO 13043 (International Standards Organization), and SAE documents have an overarching reference to “best practices.” The SAE J standards covering service equipment set specific design and test requirements to cover refrigerant flammability issues.
R-744 gets VW backing
Daimler received limited backing from Volkswagen Group, whose chairman, Ferdinand Piech, said that R-744 (carbon dioxide as a refrigerant) was the “right refrigerant.” VW said it would not be installing R-1234yf in new vehicles; however, VW hadn’t announced specific installations of R-1234yf for 2013, so long-term meaning of the statement was uncertain.
Further, attempts to use R-744 were dropped in 2010, after some 17 years of engineering effort. Although systems were developed, issues remained, including cost, durability, and ability to meet U.S. EPA restrictions. Carbon dioxide is the exhaled product of human respiration, and may affect driver performance in concentrations of 3% and higher, hence EPA use conditions. They require R-744 system designs to ensure that a short-term exposure (15 minutes or more) is within this limit, and that 4% is never reached. These percentages include carbon dioxide buildup from respiration by passengers.
If an under-dash R-744 leak from the system evaporator could breach the cabin limit, the refrigeration system might have to be confined to underhood, a packaging issue. Circulating refrigerant through an underhood heat exchanger to chill liquid coolant, and pumping it to an under-dash heat exchanger (called “secondary loop”) would be safe. But there would be a conversion loss, and energy efficiency already is a question with R-744. Over the lifetime of a properly serviced A/C, direct global warming emissions even from R-134a leakage are small compared with those from energy to operate the system.
Because R-1234yf is now available, the mandated installations were expected to proceed. Parts and service equipment suppliers that committed resources to the new refrigerant were concerned the Daimler decision would lead the EC to accept further delays.
EU denies further delays
However, this was denied by Philippe Jean, head of the applicable EC regulatory unit, in a letter to Peter Coll, Vice President of Neutronics Inc., a producer of refrigerant identifiers. Jean noted the commission had delayed enforcement of its original January 1, 2011 deadline, but said that “both suppliers of R-1234yf (Honeywell and DuPont) have confirmed that the supply situation has been solved.” He added that “after this date [January 1, 2013] European Union member states cannot allow registration of cars (those type-approved for the use of the new gas) that use the old gas R-134a.”
The EC regulator also noted R-1234yf was the industry choice, not specified by legislation. He said, “The directive (requiring a low GWP refrigerant) does not prescribe any particular refrigerant or system.”
There is no statutory fine in the EC regulation, although European environmental groups have called for fines. It is unknown if member states would forbid registration of any vehicles the EC says should contain R-1234yf. Selling and registering cars without refrigerant, then charging in dealerships with R-134a (which would provide similar performance in an R-1234yf system), is forbidden by EC regulation.
R-1234yf appeared as an ingredient in Honeywell’s Fluid H, an azeotropic blend with CF3I, a fire suppressant that rendered the proposed refrigerant nonflammable. However, CF3I was said to be a cardiac sensitizer, and objections were raised to its use. The primary ingredient, R-1234yf, was evaluated separately. It reportedly is more expensive to make than R-134a and, with patent protection in the U.S. and Europe, has only the joint-venture supplier. One Honeywell patent was overturned by the European Patent Office, but legal maneuvering seems to have a life of its own.
The GWP limit of 150 was set to allow use of R-152a. However, EPA use criteria realistically limit it to underhood secondary-loop application. R-152a is somewhat more flammable than R-1234yf, so if the Daimler question on R-1234yf is an issue, R-152a would pose an even greater one.