Engineer's Notebook: How to Design & Control Waterside Economizers PDF

Steve Taylor discusses why waterside economizers are preferred to airside economizers in some applications despite being less energy efficient. When waterside economizers are used, they usually require only the addition of a heat exchanger between the condenser water and chilled water; other components remain the same, although cooling tower approach sometimes must be reduced to meet Standard 90.1 performance requirements. Economizers should always be piped in an integrated (series) arrangement. Controls are straightforward except predicting when the economizer should be enabled which requires knowledge of wet-bulb temperature and predicted heat exchanger and cooling tower approaches. But with integrated economizer design, this prediction is not critical to reliable plant performance.