Refrigerant selections were simple-or at least simpler-until late 1989. The choices for centrifugal (turbo) chillers were among R-11, R-12, R-22, and R-500. Special needs, such as serving low capacities or operating at high condensing temperatures for heat recovery, called for R-113 or R-114, respectively. Most engineers either did not specify a desired refrigerant or were amenable to alternatives in bid reviews. They simply stipulated the capacity, operating specifications, and required piping, power, and control features.
The next most common choice was R-12, to extend the competitive centrifugal range to lower capacities and for cost advantages when high efficiency was not demanded. R-500 was introduced in centrifugal chillers to achieve the same capacities with 50-Hz motor speeds as obtained with R-12 at 60 Hz for similar designs. It later gained use in 60 Hz equipment to expand the range of capacities. Standard in Europe, parts of Japan, and elsewhere in Asia is 50-Hz power; 60-Hz power is the norm in most of North America and the remainder of Japan.