DA-76-18-1 -- Energy Characteristics of Central and Unitary Systems PDF

The large multi-story office building has traditionally been associated with chilled water type central systems by most designers. The increasing emphasis on energy consumption has raised the question of whether energy consumption could be reduced by substituting a number of small self-contained systems for the traditional central system. The purpose of this study is to explore the inherent energy characteristics of both types of systems and draw conclusions which may be of interest to the consulting engineer in the selection of the proper system type for a large office building.

It should be emphasized, however, that the energy characteristics are only one of the many factors which should be considered in the selection of an air conditioning system. Functional performance, appearance, initial cost, equipment life, and maintenance cost must all be considered in order to select the type of system which will give the desired level of performance with the lowest life cycle cost. In this connection, central systems would probably be considered to have the advantage in functional performance, maintenance cost, and life expectancy, while unitary systems would generally result in a lower initial investment cost.

For this study, a building has been selected which is considered representative of the type of moderate size office building which will be constructed for the next few years.