Each refrigerant requires its own dedicated RRR machine. Can’t wait to see what happens when R1234yf is fitted to hybrids. Another machine? Image courtesy of Robinair
The search for a replacement for R134a featured several possibilities. Nearly any gas can be used as a refrigerant. It all depends on the pressure/temperature relationship of a gas on just how effective it may be. With that in mind, let’s take a look at some of the early contenders.
One of the first to be considered was R744, or carbon dioxide. Kind of hard to beat the gas used as a baseline, isn’t it? But the use of R744 (every refrigerant receives a nomenclature beginning with the letter R) posed some problems. The system itself requires high operating pressures, in excess of 2,000 psi, and some automakers thought that was not a good thing to have in the passenger cabin.
One solution to this potential safety hazard was the use of a “secondary loop” design. In this design, a coolant fluid (antifreeze) was cooled by the refrigerant circuit and then passed into the cabin, where the coolant was used for the transfer of heat. It prevents the exposure of high pressure in the cabin by keeping all the refrigerant components under the hood, but increases cost and complexity.
Always good practice, checking the quality of the refrigerant in the car before recovery will be mandatory on R1234yf systems. It’s incorporated into the RRR equipment.
R744 is not as efficient as R134a, according to some sources, and cars equipped with this refrigerant in the U.S. might do a dandy job when the car is in Fond du Lac, Wis., but fall short when faced with the demands a city like Phoenix would place on it. In addition, the impact of greenhouse gases not only is measured as a result of the gas itself, but the energy consumed by the vehicle to operate the air conditioning system. Some claim that R744, overall, actually pollutes more when considering this additional factor.
Another potential candidate was R152a, a refrigerant commonly found in those little canned air products you use to blow the dust out of your computer’s keyboard. Its properties were similar to R134a, making system design changes relatively simple to accomplish. Unfortunately, R152a is classified as a flammable material. Considering all the stuff that can catch fire under the hood of any car, this factor could be mitigated with the addition of safety features but that represents extra cost in production.
Both alternatives also faced serviceability concerns, and raised questions on whether additional certifications should be required before allowing technicians to work on them. But let’s be real. Joe Bob doesn’t have any certifications now and is trying to fix R134a systems in his driveway based solely on how his dad used to do it back in the R12 days. Any shop that has seen a car come in with an overcharged system, or one filled with something other than the correct refrigerant, knows that requiring certification and enforcing it are two very different things.