The requirement varies based on the refrigerant blend and application:
1）. HFC Blends (e.g., R-134a, R-404A, R-507)
* Oil Requirement: Mineral oil (MO) must be partially replaced with Polyolester (POE) oil.
* Standard Guideline: Manufacturers typically recommend less than 5% residual MO, though recent studies show higher levels can still function well.
* Complexity Factor: Larger or more complex systems (e.g., those with receivers) definitely require POE addition. Note that some blends include hydrocarbons to help circulate MO.
2）. Older R-12 & R-502 Retrofit Blends (e.g., R-401A/B, R-402A/B, R-408A, R-409A)
* Below 0°F: Partially replacing MO with Alkylbenzene (AB) or POE is highly recommended.
* Above 0°F: Oil replacement is usually unnecessary, as evaporators can adequately return standard mineral oil.