An R-12 system is being retrofitted to R-134a. Why must the lubricant usually be changed?
Substitute refrigerants and oils · EPA 608 Core. The correct answer, and the reasoning behind it.
Why there are no true drop-in replacements, and fractionation in blends.
The question
An R-12 system is being retrofitted to R-134a. Why must the lubricant usually be changed?
- Mineral oil would raise the ozone depletion potential of R-134a
- R-134a reacts with mineral oil to form chlorine
- R-134a does not mix well with the mineral oil used with R-12Correct answer
- R-134a requires no lubricant at all
Why “R-134a does not mix well with the mineral oil used with R-12” is correct
Many substitute refrigerants are incompatible with the lubricants used with CFCs and HCFCs. R-134a does not mix with mineral oil, so oil would not travel back to the compressor properly, which can starve it. A retrofit usually moves to an ester oil.
Source: EPA: Test Topics; 40 CFR 82.152
Why the other answers are wrong
- Mineral oil would raise the ozone depletion potential of R-134a — Oil does not change a refrigerant's ODP.
- R-134a reacts with mineral oil to form chlorine — R-134a has no chlorine and does not create chlorine with oil.
- R-134a requires no lubricant at all — Every compressor needs lubrication.
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