A significant factor that affects chiller performance over time is the oil used by the chiller’s compressor. Oil is used to form a seal that prevents refrigerant from returning to the suction port as well as lubricate the compressor bearings, gears and shaft seals. While necessary for operation, the oil over time becomes entrained in the refrigerant and circulates throughout the system. Eventually, the oil coats the heat exchanger tubes, which creates a thermal barrier that degrades efficiency—a problem known as “oil fouling.” A number of independent third-party studies detail the consequences of oil fouling, which include: ? A drop in heat transfer ratio from 1.0 to 0.65 at oil concentrations as low as 10 percent. 2 ? A loss of 10 percent efficiency after five years, 20 percent ef

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