OIL RAC SYSTEMS
With few exceptions, RAC systems contain oil for sealing and greasing compressor. A small amount of oil will always leave the compressor and will be transported around the system (even with oil separators, in a small amount will circulate in the system).
In most systems, requires the return of oil, oil mixed with the refrigerant. Compatibility also reduces the negative impact of oil heat exchangers. Oils used with CFCs and HCFCs are not miscible with HFC, which makes oil change needed to achieve the same characteristics.
Mineral oil (MO), alkylbenzene (AB) and sometimes Poly-alpha-olefins (PAO) oils used with CFC or HCFC refrigerants, which are often replaced with POLYOLESTER (POE) of the oil at HFCs are used. Also polyalkylene glycols (PAG), oil and Polyvinylethers (PVE) are used for HFCs. PAG oil used in the automotive Air conditioning.
The "service" or "drop-in" blends are designed to achieve behaviour similar to HFC/MO or HCFC/MO to avoid the cost of replacing oil-based oil.
It should be noted that there will be significant differences that affect some systems significantly.
New oil for HFCs are hygroscopic and require preparation and proper treatment to avoid an increase in bounce rate. Large banks of oil that cannot be cleaned on a single installation, should not be used if the transportation of oil in a pressure vessel, i.e., two ports refrigerant cylinder, where it can be kept under excessive pressure of nitrogen.
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Refrigerants