This paper proposes a new index of the seasonal energy efficiency for chillers. The new index, the CSE (chiller seasonal efficiency) index, can be used by building designers for specifying the required chiller performance to manufacturers. This index has an advantage in that it is adaptable to multiplechiller systems by setting six rating points to consider the difference in the COP due to the entering condenser water temperature as well as the part load. In addition, the use of the weighted harmonic mean equation improves the accuracy in predicting the seasonal COP. In this paper, the rating condition for the CSE index is determined from the cooling load profile of office buildings in Japan. Using the CSE index, the advantage of a variable-speed compressor chiller is presented. In the final part of the paper, the effect of the difference in chiller sequence control is discussed.

Units: Dual