Design of Compressors to Meet the Performance Ranges Required for Residential Air Conditioning

The last decade has seen an increasing awareness that the manner by which a compressor meets the part load conditions of residential air conditioning is a strong dete:cninant of the a.easonal SEER of the air conditioner. The compressor can reSPond to part load needs by cycling if of the single SPeed variety, by cycling between capacity levels if of the multiSPeed variety, by use of internal capacity control, or SPeed modulation for load following. A plot of load vs ambient temperature, showing the zero load temperatures for the class of buildings in which units containing the compressor will be ap~lied may be used to indicate the range of loads, and indirectly the correSPonding pressure ratios imposed on the compressor. Lines of capacity of such units may be included to approximate the percentage of "on" time for each ambient condition if the compressor is cycled, or the required level of capacity if the compressor is modulated. When the hours per year at the various ambients are added to the plot the expected period of operation of the compressor at each pressure ratio and average capacity are revealed. Large differences in compressor operating conditions are imposed by the air conditioning unit in different geographical areas, and by different heating-cooling changeover temperatures. The SEER of the unit the compressor serves thus varies widely in different locations. Information from such an analysis is very valuable in dete:cnining the optimum design of the compressor. Examples will be given in the paper for units located in Dal]as and Chicago,