ABSTRACT
During part-load conditions, oversized vapor-compression cooling systems can waste energy by overcooling spaces. In theory, by stopping the compressor sooner in its cycle and running the evaporator fan longer, one could reduce total compressor runtime while maintaining target zone temperatures. As part of a multi-year evaluation, a temperature-feedback compressor cycling controller was on/off-tested in six commercial buildings in dry and humid climates. Results were mixed. Surprisingly, in four cases, the new control scheme caused fan runtime and ventilation loads to increase dramatically, leading to increased total system energy consumption. Two cases, with high baseline fan runtime, showed limited evidence of savings (6.5% and 17%). Several challenges with installation and commissioning were encountered. The results highlight potential risks of isolated component-level optimization.
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