ARLINGTON, VA — The General Standards Committee of the Air-Conditioning and Refrigeration Institute (ARI) has approved and released an addendum to ARI Standard 550/590-1998, “Standard for Water Chilling Packages Using the Vapor Compression Cycle.”

Standard 550/590-98 combines two previously separate standards: ARI Standard 550-92, “Centrifugal and Rotary Screw Water Chilling Packages,” and ARI Standard 590-92, “Positive Displacement Compressor Water Chilling Packages.” In 1999, ARI’s Large Tonnage Liquid Chiller Product Section voted to combine the two standards to reduce confusion in equipment application and ensure consistent treatment for rating and testing of two similar and overlapping product lines.

The combined, revised standard includes two other major changes that affect how chillers are rated and tested. These changes relate to the integrated part load value (IPLV) and the fouling factor adjustment used for evaporators in closed loop water systems.

The IPLV rating conditions and part load weightings have been changed to more closely reflect actual operating experience found in the field for a single chiller. The evaporator fouling factor has been changed from 0.00025 to 0.0001 based on research work sponsored by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), which shows that the actual fouling of the waterside of evaporators operating in closed circuit water systems experience very minimal degradation in performance over time.

The standard and addendum can be downloaded for free at

Publication date: 07/29/2002