Don’t be Stymied by Chiller Specs

When specifying chiller efficiency, some HVAC designers actually work against themselves by producing specifications that prevent them from getting what they need from the bidding process: chillers with equal annual energy consumption at the best capital cost. The problem usually occurs when two measures of chiller efficiency—the design-efficiency rating and the non-standard part-load value (NPLV) rating—are both used in the specification. So, let's dispel the confusion about these ratings once and for all. First, let's clear up some misconceptions about the NPLV rating. NPLV can be measured in kilowatt per ton refrigeration (kW/TR), coefficient of performance (COP) or energy-efficiency rating (EER).