Refrigerant Oil Types
Mineral oil (MO) is the traditional lubricant used with CFC and HCFC refrigerants such as R-12 and R-22. Alkylbenzene (AB) oil is a synthetic alternative also compatible with CFCs and HCFCs. Polyolester (POE) oil is required for HFC and HFO refrigerants like R-134a, R-410A, and R-1234yf because mineral oil will not mix with these refrigerants. Polyvinyl ether (PVE) oil is another synthetic option used with some HFC systems, particularly in certain R-410A equipment manufactured in Asia.
Mineral oil and AB oil work with CFCs/HCFCs. POE oil is required for HFCs/HFOs. PVE oil is an alternative for some HFC systems.
POE Oil: Hygroscopic Nature
POE oil is highly hygroscopic, meaning it absorbs moisture from the air very rapidly. Even brief exposure to the atmosphere can contaminate POE oil with enough moisture to cause problems in a refrigeration system. Moisture combined with refrigerant and oil forms hydrofluoric (HF) and hydrochloric (HCl) acids that corrode metal components. Always keep POE oil containers tightly sealed, and only open them immediately before use. Replace the cap promptly after pouring.
POE oil absorbs moisture rapidly from the atmosphere. Always keep containers sealed. Moisture in POE oil leads to acid formation and system corrosion.
Azeotropic vs. Zeotropic Blends
Azeotropic blends (such as R-507) behave as a single refrigerant: all components boil and condense at the same temperature, so they do not fractionate. Zeotropic blends (such as R-407C and R-410A) have components with different boiling points. They evaporate and condense over a range of temperatures called temperature glide. R-410A has negligible glide (~0.3 degrees F) but is still classified as zeotropic. R-407C has significant glide (~9 degrees F), making it more prone to fractionation.
Azeotropic blends (R-507) act as one refrigerant and do not fractionate. Zeotropic blends (R-407C, R-410A) have temperature glide and can fractionate.
Oil & Blend Quick Reference
Fractionation & Mixing Prohibitions
Fractionation occurs when a zeotropic blend leaks or is improperly charged as vapor: the more volatile component escapes first, changing the remaining blend's composition and pressure-temperature characteristics. This is why all zeotropic blends must be charged as liquid from the cylinder. You must never mix different refrigerants together in a system. Mixing creates unknown pressure-temperature relationships, can damage equipment, and produces a blend that cannot be recycled. Any mixed refrigerant must be sent to a certified reclaimer for processing.
Fractionation changes a blend's composition when the more volatile component leaks first. Never mix refrigerants; mixed refrigerant must be reclaimed.
Oils & Blends Review
- Mineral oil and alkylbenzene oil are used with CFC/HCFC refrigerants; POE oil is required for HFC/HFO refrigerants.
- POE oil is highly hygroscopic and must be kept sealed to prevent moisture absorption.
- Azeotropic blends (R-507) behave as a single refrigerant with no temperature glide or fractionation.
- Zeotropic blends (R-407C, R-410A) have temperature glide and must always be charged as liquid.
- Fractionation occurs when the more volatile component of a zeotropic blend escapes first, altering the blend's properties.
- Never mix different refrigerants. Mixed refrigerant must be sent to a certified reclaimer.