OPTIMIZED SUPPLY-AIR TEMPERATURE (SAT) IN VARIABLE-AIR-VOLUME (VAV) SYSTEMS

A criterion, based on optimization principles, for determining the SAT setpoint in VAV systems is presented. It is generally accepted that c onventional SAT reset controls (SATRC), bounded by either space humidi ty or ductwork size, will save cooling and/or heating energy. However, the ventilation consequences and penalty resulting from increased fan power have generally been overlooked. Ventilation is impacted since c hanges in the SAT setpoint change the primary airflow rate and the ope ration of economizer cycles, i.e. the distribution of fresh outdoor ai r (OA). These changes may result in extra energy demand and ventilatio n inefficiency if the reset criterion is not appropriate. This optimiz ation concept simultaneously reduces energy consumption and meets vent ilation requirements. Simulation results illustrate that the use of th e optimized SATRC saves more energy than a conventional one. (C) 1997 Elsevier Science Ltd.