In recent years there has been a growing trend toward the use of centrally located plants to supply chilled water to a number of buildings in the surrounding area, rather than having each building equipped with its own chillers, cooling tower, and controls. Advantages include reduced power requirements because of the higher efficiency of the larger central equipment, less total connected capacity because of the diversity factor (not all buildings require maximum capacity at the same time), fewer people required to operate and maintain the equipment, and greater ease of monitoring the overall operation. The chief debit is the requirement for a distribution system.

These systems are being used on college campuses, for civic centers and other clusters of government or public buildings, for airports, military bases, industrial complexes, and shopping centers. In some areas chilled water is even being sold as a utility.

Until recently, the major co~cern with a chilled-water distribution system was that it function with a minimum of problems. There was little concern over pumping costs which, while considerable, were small compared with the energy required by the chillers. With the advent of limited energy supplies,and rising fuel costs, however, this attitude is changing.