The formula was revised to improve its accuracy, especially at off-design conditions. The goal was to give chiller buyers better information with which to make energy comparisons.
However, the revised formula was derived from analysis of a single-chiller system. This has raised concerns about its applicability to multiple-chiller systems, which make up the majority of chiller plants. This article will explain the components of the formula, what makes multiple-chiller systems different from single-chiller systems, and why the formula works for both types.