New Alternative Refrigerants

By Larry Carley c2008

Nobody knows exactly how refrigeration systems will change in the future, but it appears likely that R-134a's days are numbered. The Europeans have decided to phase out R134a in new vehicles starting in 2011, with a complete phase-out by 2017. The European rules require any new refrigerants must have a global warming potential of less than 150.

Though R-134a poses no danger to the ozone layer if it escapes into the atmosphere, it is a "greenhouse gas" with a fairly high global warming potential of 1300 (compared to 1 for carbon dioxide, which is nature's own greenhouse gas). A leak that allows only an ounce or two of R-134a to escape into the atmosphere may not seem like a big deal, but over time it all adds up, especially when you multiply small leaks times the hundreds of millions of vehicles that now share planet Earth with humanity.

The Europeans want future A/C systems to be as environmentally benign as possible. That means no chlorine-containing CFCs that cause ozone depletion and as little greenhouse gas effect as possible to reduce global warming. The new refrigerant also must be nontoxic and safe - though that doesn't necessarily mean nonflammable.

In an effort to address these issues, the Alliance for Responsible Atmospheric Policy (ARAP) and the U.S. Environmental Protection Agency (EPA) hosted the Second International Mobile Air Conditioning Summit (MAC Summit '04) in conjunction with the 15th Annual Earth Technologies Forum, April 13-15, at the Hyatt Regency in Washington, DC. The Summit was organized in corporation with the European Commission, The Australia Greenhouse Office, the Japan Ministry of Environment and global industry associations.

The first MAC Summit was organized in 2003 by the European Commission in Brussels to address regulating or phasing out HFC-134a in vehicles sold in Europe. The 2003 MAC Summit was influential in persuading the European Commission to allow carbon dioxide, HFC-152a and other refrigerants as replacements for HFC-134a.

Since the leading contenders that may eventually replace R-134a are plain ol' carbon dioxide, or a close-cousin to R-134a called HFC-152a, we'll take a look at how well these substances will work as refrigerants, as well as their drawbacks.

CO2

CO2 requires extremely high operating pressures (up to 1,800 psi on the high side, and 350 to 400 psi on the low side - compared to 300 to 400 psi on the high side for R-134a). The reason the pressures are so high is because CO2 does not condense in the refrigeration circuit. It remains in the gaseous state. Consequently, the front heat exchanger is called a "cooler" rather than a condenser.

CO2's main attribute is that it has virtually no impact on global warming or ozone depletion. CO2 is also nontoxic in small doses but concentrations over 5% can be lethal. It is also cheap (about $10 for a 20-lb. cylinder) and nonflammable. A number of test vehicles are running with CO2 A/C systems and cooling performance seems to be comparable to R-134a. SAE is still working on service fitting standards, and leak detection presents a challenge because natural levels of CO2 in the atmosphere may be higher than the amount emitted by a leak. Some type of ultrasound or infrared equipment may be required to find leaks, but dyes may also work or plain old soap bubbles.

HFC-152a

HFC-152a, on the other hand, is almost a straight drop-in substitute for R-134a. The molecule is similar to R-134a except that two hydrogen atoms are substituted for two fluorine atoms. It has similar operating characteristics to R-134a but cools even better. One test in an otherwise unmodified Saturn Ion found that A/C duct outlet temperatures were several degrees C lower with HFC-152a. Fuel efficiency was also up 10% at idle, and 20% at highway speeds. The system typically requires only about two-thirds of the normal charge with HFC-152a and can be used with current desiccants.

An environmental benefit of HFC-152a is that it has a global warming rating of 120, which is 10 times less than R-134a, but still a lot higher than CO2. That is why HFC-152a is currently used in many aerosol products as a propellant. Its main drawback is that it is slightly flammable (Class 2A), but it is not as flammable as propane or most other hydrocarbon-based refrigerants.

The first mobile A/C system to use HFC-152a was unveiled at the Mobile Air Conditioning Society (MACS) Worldwide tradeshow in January 2004; a self-contained unit for off-road construction equipment that featured an oil-driven compressor. Made by Red Dot, the unit may be the forerunner of future HFC-152a A/C systems to come.

Red Dot staff explained that the HFC-152a refrigerant used in the self-contained unit improves cooling capacity, decreases fuel use and helps protect the climate. The new technology also satisfies stringent new regulations proposed by the European Commission. Red Dot staff also said that the HFC-152a system uses new technology that will use hydraulic-driven compressors and secondary loop technology to increase reliability, safety and reduce the amount of refrigerant required.

The Australian Minister for Environment and Heritage, Dr. David Kemp, said the Red Dot technology is one of three new projects undertaken under the Australia-United States Climate Action Partnership (CAP). CAP projects assist the development of innovative new technologies to help reduce synthetic greenhouse gases, which have a greenhouse impact thousands of times greater than carbon dioxide.

Dr. Kemp said: "The impact of HFC-134a - the refrigerant typically used in air conditioning in cars and trucks - was approximately 1,300 times greater than that of an equivalent amount of carbon dioxide."

HFO-1234yf

Another new refrigerant that is being considered is HFO-1234yf. Developed jointly by Honeywell and DuPont, it is being promoted as a possible drop-in replacement for R-134a in both new vehicles and older vehicles, should that become necessary in the future. HFO-1234yf has thermal characteristics that are very similar to R-134a, so no major modifications to the A/C system are necessary. Better yet, HFO-1234yf has a global warming potential of only 4, compared to 1200 for R-134a, allowing it to meet the European requirements for a GWP of less than 150. Existing refrigerant leak detectors can also detect HFO-1234yf if it leaks. But HFO-1234yf is mildly flammable (though less so than HFC-152a), and long term toxicology tests are still underway.

Click Here for a DuPont brochure on HFO-1234yf.

How Shops Will Be Affected

If the European auto makers go to CO2 as their new refrigerant rather than HFO-1234yf or HFC-152a, it will require a major redesign of existing A/C system components as well as all-new service procedures and equipment. If they opt for HFC-152a or HFO-1234yf, it may require adding special safety valves to vent refrigerant away from the passenger compartment in the event of a leak or accident, or with HFC-152a using a "secondary loop" cooling system that eliminates the evaporator and substitutes a pair of heat exchangers to circulate chilled water into the passenger compartment. Either way, the change won't affect aftermarket for years.

EPA Says It Will Not Restrict R-134a Sales

Sales of R-134a refrigerant will not be restricted, according to a rule that was finalized by the EPA in February, 2004. In a release by the Automotive Parts & Service Alliance (APSA), the EPA had proposed in June 1998 to restrict the sale of the refrigerant to only certified users, but had not finalized the proposal due to opposition from some aftermarket associations, including Automotive Aftermarket Industry Association (AAIA) and Automotive Refrigeration Products Institute (ARPI).

However, MACS agreed with the restriction proposal. In its report to the EPA in May 2002, MACS argued that the release of HFC-134a refrigerant to the atmosphere during service of a mobile A/C system is illegal and detrimental to the environment. With the availability of R-134a to the general public, there has been minimal enforcement related to the venting of refrigerant by consumers who service their own automotive systems or unprofessional service personnel who do not have the federally mandated refrigerant recovery equipment.

The EPA had based its proposed sale restrictions on the issue that car owners converting their vehicle A/C systems to R-134a would vent into the atmosphere any R-12 that remained in the system.

AAIA and ARPI said it opposed the EPA's proposal, and questioned its authority under the Clean Air Act to take such action, focusing on the issue that the restriction would unfairly impact low- and fixed-income individuals who are forced to work on their own vehicle A/C systems for economic reasons.

NEWS UPDATE: 3/7/2007: California Air Resources Board proposes ban on DIY R134a Sales. Click Here for details.

A/C Car Care Tips

"There's a simple test for any A/C system," says Paul DeGuiseppi, manager of service training for the Mobile Air Conditioning Society (MACS) Worldwide. "Set all the controls for maximum cooling, close all the doors and windows, start the engine and run it for about five minutes. It's important that you have the vehicle in the shade or out of direct sun when performing this check. If the temperature from the panel outlets gets cold, there a good chance the system is operating properly. If you have a thermometer, place it in a center outlet, and if it's a warm day and the temperature inside the vehicle is below 50 degrees F, it's a good sign that the system is cooling."

If the system is operating properly, there is no need to have the system serviced.






Related Articles:

Alternative Refrigerants
California proposes ban on R134a sales to motorists
Information about Retrofitting older vehicles with R-12 A/C systems to R-134a
Troubleshooting Air Conditioning Problems
How To Recharge Your Car's Air Conditioner
Refrigerant Contamination

To More Technical Info Click Here to See More Carley Automotive Technical Articles

Related Links:

Alliance for Responsible Atmospheric Policy (ARAP)
DuPont Refrigerants
EPA FAQs on Alternative Refrigerants
Fluorocarbons.org

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