Determinants of low energy performance in a multi-chiller system serving an educational premise

This study analyses an association between operating variables and low energy performance in terms of the coefficient of performance (COP) of a chiller system in daily operation. Year-round operating data were collected at 15-min intervals from a trend logging device for a system with five chillers of two different capacities. Two-step cluster analysis was applied to group operating data with high and low COP ratings. The odds ratio analysis ascertained that the key deficient control was operating extra chillers with one at particularly light loads. The optimal trade-off between the chiller power and condenser water pump power was not achieved due to the surplus operation of condenser water pumps. The low COP rating was also due to an imprecise control in the chilled water supply temperature and the condenser water entering temperature from their fixed set points. The significance of this study is to prioritize COP improvement opportunities by ranking the impact of deficient controls based on the actual configuration and operating practice of any given chiller system.