Why Replace Refrigerant R12?
Refrigerant R12 or Freon 12 is the most widely used of all the refrigerants for different refrigeration and air conditioning applications. R12 is a highly versatile refrigerant that can be used in wide range of the operating conditions without getting disintegrated. The whole field of the refrigeration has become much easier and useful mainly because of R12 refrigerant.
Unfortunately, R12 is a chlorofluorocarbon (CFC) with the chemical formula CCl2F2. It has unusually high potential to cause the depletion of the ozone layer in the upper layers of the atmosphere that causes the greenhouse effect. Due to this, as per the Montreal Protocol, R12 has to be phased out completely by the year 2021. It is very difficult to find alternative replacements for such a widely used refrigerant, however, a few of the viable replacements to R12 have been found.
Replacements for R12
The best replacement for R12 is considered to be R-134a. The chemical name of R134a is tetrafluoroethane and it chemical formula is CF3CH2F. It is a hydrofluorocarbon (HFC) and has zero ozone depletion causing potential and very low greenhouse effect. R-134a is nonflammable and non-explosive and has good chemical stability though it has some affinity towards moisture.
The other two refrigerants that are considered good replacements for R12 are R-401a and R-401b. R-401A is the mixture by weight of 53% of R-22, 13% R-152a and 34% R-124. It is good replacement for R12 in the applications where the evaporator temperature is -23 degree C and above. It can be used applications like walk-in coolers, food and dairy display cases, domestic refrigerators, and beverage dispensers and vending machines.
R-401b is the mixture by weight of 61% R22, 11% R-152a and 28% of R-124. This refrigerant is suitable for domestic and commercial freezers and transport refrigeration.
Why R-134a is the Best Replacement for R12
Among all the alternatives available for R12, R-134a is considered to be the best available option because it has favorable toxicity data and good chemical stability. This refrigerant has been tested by the chemical industry’s Program for Alternative Fluorocarbon Toxicity Testing (PAFTT) and the results indicate that if does not pose the hazards of cancer and birth defects.
R-134a is nonflammable and non-explosive, however its mixture with air is found to be combustible at high pressures and they can cause injury or property damage. R-134a is non-corrosive with the copper, aluminum and standard steel materials. R-134a is the single component refrigerant and not the blend like the other alternatives. While handling R-134a, the technicians should work in the ventilated place and should avoid inhaling the gas.
How easy is Replacing R12?
The switchover from R-12 to other refrigerants is quite a simple procedure. Firstly, the old refrigerant R-12 has to be removed from the system and recovered (as per the EPA this refrigerant should be returned back and it is illegal to release it to the atmosphere). Then the lubricant of the refrigeration system has to be changed along with the filter and drier. Once this is done, the refrigeration system can be charged with the new alternative refrigerant. In some systems minor change in the settings of the expansion valve and other controls may be required.
The alternative refrigerants are not compatible with the mineral oil used as the lubricants with R12 refrigerant. Thus when new refrigerants are used, the compressors should be charged with the synthetic lubricants like alkylbenzene synthetic. To remove the oil completely, flushing of the system is required or the maximum amount of the old oil that can remain in the system is 6% of the total lubricant inside the system.
R12 Replacement for the Vehicles
In most of the vehicles, the air conditioners use the R12 refrigerant, which is now getting difficult to get and expensive. For vehicles also the most appropriate alternative is R-134a refrigerant. It has been approved by all the vehicle manufacturers for replacing the R12 refrigerant. By following the proper replacement procedures one can get the same cooling effect in the car as with the previous refrigerant. The vehicle manufactures do not prefer the blends as the alternative refrigerants since there are chances that they may disintegrate in the extreme operating conditions.
As a vehicle owner, if you are replacing R12, remember that there is no drop-in replacement for it. As per the Federal law it is illegal to top-of the air conditioning system with the other refrigerant that is chemically different from the original one. It is required that first the old refrigerant be removed from the system so that it can be converted into alternative refrigerant system. If you are charging the system with R-134a, then the amount of refrigerant required is 80-90% of the R12 refrigerant amount required by the system.
Two lubricants are being used commonly with the R12 retrofitted systems, these are: PAGs and esters. PAGs are hydroscopic in nature so they have tendency to absorb the atmospheric moisture that can limit it lubricating capacity, due to this many manufacturers are using esters that are less hygroscopic nature.
1) Book: Principles of Refrigeration by Roy J. Dossat, fourth edition, Prentice Hall