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Differences between R12 and R134a


One of the differences between R-134a and R-12 is the boiling points. Pure R-12 will boil at -22 degrees Fahrenheit while R-134a boils at -16 degrees Fahrenheit. If we hooked up a gauge to a bottle of R-12 refrigerant which contains liquid, we would have about 117 PSI at 100 degrees F. The pressure of reading of R-134a at that same temperature would be about 124 PSI. For this simple fact, R134a gauge readings will be a little different as compared to R12. While the overall temperature curve is different and the critical temperature is lower, during most operating conditions, you'll find R-134a is a fairly close match to R12. R-134a is slightly less efficient and condensers will usually have to be upgraded to match the cooling performance of R12.


Another difference is the the type of lubrication that will required when using R-134a. For years, most R12 compressors required a standard 525 SUS viscosity mineral oil. Mineral oil will not mix well with R-134a. They seem to coexist just fine, but, since mineral oil is not miscible with R-134a, you'll need to use a suitable oil. PAG oil is what most OEM's recommend for use with R-134a in automotive systems.


There are also political, economic, and safety considerations between the two chemicals which remain outside the scope of this basic informational article.

For more information on R-134a, please visit the following sites:

Genetron Refrigerants

DuPont Refrigerants

U.S. EPA: Guidance on Retrofitting to HFC-134a 










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