Converting From Primary/Secondary to All-Variable Flow

The control of all-variable-flow chilled-water systems is thought to be so complicated and, thus, difficult for operators to understand that many engineers and designers resist converting their primary/secondary systems, even though the return on investment of such a conversion is measured in weeks, rather than years, with chilled-water-plant energy consumption reduced by at least 10 percent and often by 20 percent or more.

The performance of a central chilled-water plant was docume