HEAT SOURCE SYSTEM

A heat source system includes a plurality of heat source apparatuses each including a refrigerant circuit including a water heat exchanger; a water supply header pipe configured to merge and supply, to a load, water flowing in from the plurality of water heat exchangers; a water return header pipe configured to split, into the plurality of water heat exchangers, water flowing in from the load; a plurality of pumps configured to feed water to the plurality of water heat exchangers; a bypass pipe configured to connect the water supply header pipe and the water return header pipe; a bypass valve provided on the bypass pipe; a differential pressure gauge configured to measure a water pressure difference between pressure of water supplied to the load and pressure of water returning from the load; and a controller configured to control the plurality of heat source apparatuses and the plurality of pumps, where the controller determines the number of heat source apparatuses to be operated, among the plurality of heat source apparatuses, from an amount of heat generated by a plurality of the refrigerant circuits and an amount of heat required, determines whether an operating frequency of the pump connected to a heat source apparatus to be operated is a minimum frequency or not, and controls, according to a result of determination, one of the operating frequency of the pump and an opening degree of the bypass valve such that the water pressure difference falls within a target range.