Drop-In Refrigerants

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Last updated: 
February 19, 2024

R22 Drop-In Replacements: Considerations and Alternatives

The Phase-Out of R22 Refrigerant

R22 has been the most common refrigerant in residential and light commercial air conditioning applications. However, due to its damaging effects on the ozone layer, R22 has been phased out, with availability limited to existing stockpiles and recovered refrigerant from decommissioned machines . The sale of new equipment containing R22 has been stopped, although R22-compatible units can still be shipped "dry" and charged with R22 during installation .

The Debate Over Drop-In Replacements

The phase-out of R22 has left many systems stranded before reaching end-of-life. Some market players claim that drop-in replacements are safe and effective, while others argue that equipment should be replaced with new systems designed for R410a, a higher pressure refrigerant . There is also disagreement over whether drop-in refrigerants can be mixed with residual R22, with some suggesting a complete flush and replacement using nitrogen to ensure a clean transition . However, this can be challenging when lines are concealed or evaporator coils are difficult to access, in which case drop-in replacements may be preferred over switching to R410a .

Alternative Drop-In Refrigerants

While recycled R22 remains available for repairing existing systems, two HFC-based drop-in alternatives with zero ozone depleting potential are being promoted by DuPont:

  1. DuPont™ ISCEON® MO29 (R422D): A non-ozone depleting blend of R125, R134a, and R600a used to replace R22 in various refrigeration and air conditioning applications. It closely matches R22's capacity and efficiency in most systems while having a significantly lower discharge temperature that may prolong compressor life. MO29 is compatible with traditional and new lubricants, allowing for easy, cost-effective retrofits .

  2. ISCEON® MO59 (R417A): Another non-ozone depleting blend (R125, R134a, R600) typically used to replace R22 in direct expansion stationary air conditioning and medium temperature refrigeration systems. MO59 also has a lower discharge temperature than R22, potentially extending compressor life. While it may provide energy savings, some systems could experience reduced capacity. Like MO29, it is compatible with various lubricants and allows for easy retrofits .

Considerations When Using Drop-In Replacements

According to reports, refrigerant leaks are common after replacing R22 with either R417A or R422D, as these alternatives do not swell elastomeric seals like R22 does . Our research suggests that changing all elastomeric seals in contact with the refrigerant during the replacement process is recommended . With recycled R22 available until the end of 2014, there is no legislative need to switch to drop-in alternatives presently unless the ozone depleting potential of R22 is a concern .

Major Manufacturers' Opinions on Drop-In Replacements

ToshibaNot tested replacement refrigerants; R417A found to decrease performance by 6-10% and increase power consumption by 15-25%; mineral oil should be replaced with poly oil; use at contractor's discretion .
SanyoRecommends R417A for all Sanyo R22 systems, including VRF; several systems charged with R417A over 10 years ago with no noticeable performance impact .
Mitsubishi ElectricOfficial guideline is not to use drop-in replacements as they may reduce efficiency and shorten compressor life; client assumes risk if used .
FujitsuHas not tested drop-in refrigerants; cannot comment on system life expectancy or efficiency if used .

Considering R410a as an Alternative

R410a is a refrigerant that may be considered when faced with the R22 changeover. However, it is important to note that R410a is very different from R22, with much higher discharge pressures. As a result, an R22 system cannot be directly charged with R410a since the components are not rated for the higher pressures . Despite this, R410a is seen as a suitable replacement for R22 due to its high cooling capacity (up to 40% higher than R22), easy servicing (behaves more like a pure refrigerant), and safety (A1 ASHRAE classification) .

In conclusion, while drop-in replacements for R22 exist and may be suitable in certain situations, it is crucial to consider the potential risks and consult with professionals before making a decision. Manufacturers have varying opinions on the use of drop-in replacements, and the long-term effects on system performance and longevity should be carefully evaluated.


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