This paper describes a simulation model and life-cycle cost study used to develop a fan speed control requirement for cooling towers, evaporative condensers, and air-cooled condensers as part of ASHRAE/IESNA Standard 90.1-1999, Energy Standard for Buildings Except Low-Rise Residential Buildings. A joint working group consisting of members from ASHRAE TC 8.6 and ASHRAE/IESNA SSPC 90.1 undertook this study, employing a national energy model developed by a national laboratory and a computer model of a central chilled water plant. The results from the study supported development of a new requirement for fan speed control on all fans over 5 hp (3.7 kW). The SSPC90.1 subsequently expanded the model to evaluate the impacts of controls on multiple cell towers and condensers with multiple fans. These requirements were adopted as part of the published standard in 1999.

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