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Although water-cooled chillers are more energy efficient than air-cooled chillers, a majority of chilled water systems use air-cooled chillers. In cold weather climates, air-cooled chillers are capable of functioning in low ambient temperatures with few operational concerns, where as water-cooled chiller systems must be equipped to prevent cooling tower freezing. The integrated chiller system attempts to take advantage of each chiller’s strengths and eliminate any cold weather operational concerns. An integrated chiller system includes a cooling tower and air-cooled condenser. During the summer, both the cooling tower and air condenser can be operated. In cold weather, the cooling tower is drained and the air condenser is used to dissipate the heat of the cooling system. The integrated chiller system eliminates the water storage tank and frequent charging and discharging of the cooling tower system. It reduces the size of the mechanical room and simplifies the operation of the system. The integrated chiller system is most suitable in climates where the mechanical cooling is required on a short-term basis during cold weather periods. This paper presents the system configuration, system design, optimal control, and energy impact. An example is used to demonstrate the design concepts of the integrated chiller systems.