MONITORED AIR HANDLER PERFORMANCE AND COMPARISON WITH A SIMPLIFIED SYSTEM MODEL
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The retrofit of dual-duct, constant-volume systems to variable-air-volume systems has become common in recent years. Air-handler measurements can be used to explain the degree to which such retrofits do or do not provide expected operating savings. A dual-duct, constant-volume air handler in a large engineering center in central Texas that was retrofitted to a variable-air-volume system in March 1991 has been instrumented to monitor temperature and relative humidity at various locations, airflow rate, pressure drop, electric consumption of the fan motor, and runtimes of the hot and chilled-water pumps. The monitored data from the air handler prior to retrofit are presented in this paper. Significant differences between design performance and measured hot deck and cold deck temperatures and outdoor air fraction as a function of outdoor temperature were found. The measured data are also compared with the predictions of a partially calibrated simplified systems model based on the TC 4.7 simplified energy analysis procedure (Knebel 1983).