Low Superheat, Chiller, Electronic Expansion Valve, SEER, Variable Speed
The adoption and proliferation of variable speed compressors and electronic expansion valves (EXVs) in high-efficiency reversible chiller systems provides the opportunity to optimize the performance of the unit around a new set of variables. This paper details the benefits of a controls framework designed to enable low-superheat (below 5K) operation to optimize the seasonal energy efficiency ratio (SEER) of a commercial-scale chiller in a safe manner. The various attributes of low-superheat operation over conventional (>5K) chiller operation, including the reliability impact on the controller and compressor, is discussed. The performance benefit for a range of capacities and compressor configurations, with particular attention to evaporator effectiveness, is also presented. In addition, the results of the associated reliability campaign to guarantee the integrity of the system for continuous low-superheat operation is detailed. Ultimately, this provides a template from which significantly improved system performance can be achieved.