The type of refrigerant used in automotive air conditioning systems depends on the year, make and model of your vehicle. R-134a refrigerant was used until recently in late model vehicles, most new cars and light trucks are now being equipped with A/C systems that use R-1234yf refrigerant. Other refrigerants are still being considered as alternatives down the road, but for now it looks as if R-1234yf will be the primary refrigerant. The Europeans phased out R-134a in new vehicles in 2017. European rules require any new refrigerants to have a global warming potential of less than 150. The U.S. EPA also wants car makers to use R-1234yf to lower the overall carbon emissions of the vehicle fleet. The latest EPA rules say vehicle makers must discontinue using R-134a in new vehicles built for the North American market after model year 2021. R-134a can still be used for some export vehicles, but only until 2025. After that, R-134a will be discontinued in new vehicles – although production will continue for servicing older vehicles that have R-134a A/C systems. Carbon credits will be given to auto makers who make the switch to a refrigerant that has a lower Global Warming Potential (GWP). 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. According to November 2006 report by the Energy Information Administration, vehicles in the U.S. leaked 50.8 thousand tons of R-134a into the atmosphere, equivalent to to over 66 million tons of greenhouse gases. The emissions are 7% higher than in 2004, and up 273 percent since 1995. North American auto markers began replacing R-134a A/C systems with ones designed for R-1234yf. Auto makers are also redesigning their A/C systems following goals in mind: * To use less refrigerant. Some newer A/C systems now use only 13 to 18 oz. of refrigerant, which is much less than the 24 to 60 oz. charges that most older A/C systems use. As time goes on, we will see more and more of these low capacity A/C systems in new vehicles. * To reduce refrigerant leakage 50% over the life of the vehicle. This requires using improved seal designs, hoses and o-ring connections. * To improve cooling efficiency 30% with more efficient condensers, compressors and operating strategies (things like variable displacement compressors that run all the time rather than cycle on and off). Mercedes has this now. * To reduce the cooling requirements inside the passenger compartment 30% by using reflective coatings on glass, heat reflective paint, and venting the interior during hot weather. Changes are also being made to reduce refrigerant losses when the A/C system on a vehicle is serviced. The latest generation of refrigerant recovery machines do a better job of removing all of the refrigerant from the system. Older machines can leave as much as 20 to 30 percent of the old refrigerant charge in the system. The residual refrigerant can escape into the atmosphere when the A/C system is opened to replace parts. Some of the newest machines can pull up to 95% of the refrigerant out of the system to reduce the amount of R-134a that escapes into the atmosphere. Auto makers have also been adding leak detection dye to the refrigerant in some vehicles to make it easier for technicians to detect refrigerant leaks. A leak will leave a telltale stain that glows greenish-yellow or greenish-blue when illuminated with an UV light source. Leaks as small as 1/8 oz. of refrigerant per year can be detected this way. The Europeans auto makers are still considering other refrigerants as possible alternatives to R-134a and R-1234yf in future vehicles. They want A/C systems to be as environmentally benign as possible. That means no chlorine-containing CFCs that cause ozone depletion, an no refrigerants that could add to the global warming problem (which includes R-134a). Any new refrigerants must also be nontoxic and safe, though that doesn't necessarily mean nonflammable. For more information, see Flammable Refrigerants In an effort to address these issues, a group called the Alliance for Responsible Atmospheric Policy (ARAP) and the U.S. Environmental Protection Agency (EPA) held a series of meetings to discuss and evaluate alternatives to R-134a. The first of these meetings was held in 2003 by the European Commission in Brussels. As a result of that meeting, the European Commission decided to allow carbon dioxide, HFC-152a and other refrigerants as possible replacements for R-134a. CO2 as an Alternative Refrigerant When used as a refrigerant, CO2 (called R-744) 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. Numerous test vehicles with CO2 A/C systems have shown that CO2 does provide cooling performance comparable to R-134a. Mercedes has been a big supporter of R-744 as an alternative refrigerant, and has used it in S_Class models. SAE has developed service fitting standards for R-744. Leak detection presents a challenge because natural levels of CO2 in the atmosphere may be higher than the amount emitted by a leak from an A/C system. Some type of ultrasound or infrared equipment may be required to find R-744 leaks, but dyes may also work or plain old soap bubbles. R-152a R-152a (HFC-152a) 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 back in January 2004; a self-contained unit for off-road construction equipment that featured an oil-driven compressor. Made by Red Dot, the unit was a 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. R-1234yf The newest refrigerant that is currently replacing R-134a in late model vehicles is R-1234yf (also called HFO-1234yf). Developed jointly by Honeywell and DuPont, R-1234yf has thermal characteristics that are very similar to R-134a, so no major modifications to the A/C system are necessary. Better yet, R-1234yf has a global warming potential of less than one (less than CO2). Originally, R-1234yf had a GWP rating of 4. But the rating was lowered to less than one because R-1234yf breaks down quickly (10.5 days) if it leaks out of an A/C system (compared to 13.4 years for R-134a). The GWP rating for R-134a, by comparison, is a whopping 1200! Existing refrigerant leak detectors can also detect R-1234yf if it leaks. But R-1234yf is mildly flammable (though less so than HFC-152a), causing some German auto makers to question its safety. Further testing proved it is safe to use in automobiles. R-1234yf is typically sold in 10 pound containers due to its high price (currently $60 to $70 per pound!). Consumers and do-it-yourselfers can purchase small cans of R-1234yf to recharge their A/C systems. Click Here for detailed information about R-1234yf by Honeywell. R513a A new refrigerant blend for possible use in retrofitting current R-134a A/C systems is a blend of 56 percent R-1234yf and 44 percent R-134a. Performance is almost identical to R-134a, yet the blend reduces the refrigerant's Global Warming Potential (GWP) to 573 (versus 1430 for R-134a). The refrigerant is under consideration for possible use in Europe because several countries in Europe are limiting imports of R-134a because of its high GWP. Historical News about Alternative Refrigerants: November 2008 SAE Says HFO-1234yf is Best Alternative Refrigerant for R-134a The Society of Automotive Engineers (SAE) International Cooperative Research Program (CRP) says HFO-1234yf offers "superior environmental performance" for future mobile air conditioning systems that may be redesigned for alternative refrigerants. The CRP1234-1 and CRP1234-2 programs, launched in 2007, have i…

Fonte: AA1Car.com