In the case of the chiller, oil was the culprit. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has been warning that oil entrained in the refrigerant of a chiller significantly degrades performance, resulting in capacity loss - and higher utility bills.
In one ASHRAE research project (601-TRP), samples of refrigerant from 10 randomly selected operating chillers were analyzed for oil content. All of the chillers were found to contain excess oil in varying amounts. The three with the lowest amounts had been serviced and had their refrigerant recycled in the last six years, but the oil content in these three ranged from 3 to 7 percent. The oil content in the refrigerant of the remaining chillers ranged from 9 percent to more than 20 percent.