What is the potential impact on performance if you mix refrigerants when converting to a low-GWP alternative?

What is the potential impact on performance if you mix refrigerants when converting to a low-GWP alternative?

• A. Cross-contamination alters pressures, lubricants, and efficiency; often requires full purge and flushing.
• B. Mixing refrigerants has no effect on performance.
• C. Cross-contamination always improves lubrication.
• D. Mixing only affects the color of the oils.

Answer: (A)

Mixing refrigerants introduces a blend with unknown properties. When residues of the old refrigerant mix with the new low-GWP refrigerant, the resulting mixture can have different pressures, temperatures, and oil compatibility than either refrigerant alone. That changes suction and discharge pressures, superheat behavior, and overall efficiency, and it can also alter how the oil mixes with the refrigerant—potentially diluting or degrading lubrication. These unpredictable changes raise the risk of compressor wear or failure. To avoid these issues, a full purge and flush remove residual refrigerant and oil so the system can be charged with the intended refrigerant and fresh oil. The other ideas—no effect, guaranteed lubrication improvement, or oil color changes—don’t reflect the real risks of cross-contamination.

Mixing refrigerants introduces a blend with unknown properties. When residues of the old refrigerant mix with the new low-GWP refrigerant, the resulting mixture can have different pressures, temperatures, and oil compatibility than either refrigerant alone. That changes suction and discharge pressures, superheat behavior, and overall efficiency, and it can also alter how the oil mixes with the refrigerant—potentially diluting or degrading lubrication. These unpredictable changes raise the risk of compressor wear or failure. To avoid these issues, a full purge and flush remove residual refrigerant and oil so the system can be charged with the intended refrigerant and fresh oil. The other ideas—no effect, guaranteed lubrication improvement, or oil color changes—don’t reflect the real risks of cross-contamination.