Abstract: Provided is a heat source system that includes two heat source devices connected in series to a heat medium and can be efficiently operated. A heat source system (1) reduces the temperature of chilled water that is guided from a cooling load and has a predetermined return temperature Tr, to a predetermined supply temperature Ts, and supplies the chilled water to the cooling load. The heat source system (1) includes: a second centrifugal chiller (TR2) that reduces the temperature of the chilled water from the return temperature Tr to an intermediate temperature T2; a first centrifugal chiller (TR1) that reduces the temperature of the chilled water that has been reduced to the intermediate temperature T2 by the second centrifugal chiller (TR2), to the supply temperature Ts; and a control unit (9) that variably sets the intermediate temperature T2.

Abstract: A chiller control apparatus increases or decreases chillers in order to efficiently operate an entire chiller system. When the number of chillers increases, an insufficient load value calculation unit calculates an insufficient amount of a load for a required load. Then, using a COP obtained according to an operating environment of the chiller, a chiller-to-be-operated selection unit selects, from among stopped chillers, a chiller having the highest COP when operated with an insufficient amount of a load, as the chiller to be subjected to stage increase. Further, when the number of chillers decreases, an operation pattern extraction unit extracts operation patterns that are combinations of chillers to be operated according to the required load.