HCFCs like R-22 may cause elastomeric gaskets and seals to swell or harden. When the R-22 is removed and replaced with any of the HFC replacements, drop-in or other, gasket and seal shrinkage may occur. This shrinkage of gaskets and seals may cause leaks to develop after the retrofit is complete. This shrinkage is not caused by the HFC refrigerant but by the removal of the HCFC R-22. Leaks will not always occur but may be avoided by replacing elastomeric seals during the retrofit. Schrader cores, Schrader valve caps, ball valves, solenoid valves, and flange gaskets are just some of the seals that may be affected.
On many residential and light commercial A/C systems, the Schrader cores and caps are the only things that will need replacing. On larger refrigeration and A/C systems, many gaskets may need to be replaced or monitored after the retrofit. Filter driers must be added or changed during any retrofit.
Many drop-in replacement refrigerants on the market will not require an oil change in close coupled systems or systems that don’t utilize a liquid receiver. However, on larger systems and systems that do utilize a receiver, oil return may become an issue. The refrigerant manufacturer or compressor manufacturer will instruct you to add some percentage of POE oil to the existing mineral oil to aid in oil return. POE oil is a good solvent and will loosen any deposits or debris that is in older systems. For this reason, multiple filter drier changes may be required after the retrofit has been completed.
When retrofitting to a new HFC refrigerant that requires the system oil being completely changed to POE, the same problem can occur. The POE oil will loosen deposits and debris. When changing the system to POE, multiple oil changes will be required to achieve a high percentage of POE oil. A refractometer can be used to check that the percentage of POE in the system is high enough for proper retrofitting. To speed up full oil change retrofits, the old MO can be flushed out with RX11 flush. This not only will be faster than multiple oil changes but it will also clean out system debris.
As with any refrigerant retrofit or conversion, consult with the compressor manufacturer.