ASHRAE 90.1-2013 specifies that “Water economizer systems shall be capable of cooling supply air by indirect evaporation and providing up to 100% of the expected system cooling load at outdoor air temperatures of 50°F dry bulb/45°F wet bulb and below.” Many engineers size the components involved in the economizer (cooling tower, cooling coils and ductwork or piping serving constant load spaces) solely for their primary function without considering how these components affect the ability to meet the above requirement. This presentation discusses whether the above requirement can be met and what are the implications for selection of the components.
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