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ABSTRACT

Single-duct variable-air-volume (VAV) systems are widely used to condition buildings in the United States. When such a system serves multiple zones with different load profiles, simultaneous cooling and heating frequently occur. To avoid this inefficient scenario, dual VAV systems, where one VAV system provides cooling and the other provides heating, could be used. This paper proposes a new configuration for dual VAV systems to improve their operation to reduce the loads on cooling and heating equipment and thereby total energy use. The proposed configuration and its sequence of operation can reduce cooling and heating loads by eliminating simultaneous heating and cooling and maximizing the use of outdoor air (OA) for cooling and return air for heating. The performances of both single and dual VAV systems are simulated for given buildings and for different locations to estimate load reductions and fan energy savings achieved by the proposed dual VAV system configuration and control strategies. The simulation results that show significant heating load reductions of up to 89%, great fan savings up to 15%, and minor cooling load reductions of around 1% can be obtained, depending mainly on load variations and locations.