An air conditioning system includes an outdoor unit, indoor units, a controller that controls the outdoor unit, and an equipment controller. The equipment controller stores a set lower limit value that is set to maintain a pressure difference between the high pressure and the low pressure in the outdoor unit at a predetermined value or greater. The lower limit value is set to be smaller as a minimum cooling capacity increases. The minimum cooling capacity is the minimum value of a cooling capacity of an indoor unit arrangement formed by the indoor units. When starting a cooling operation, the equipment controller determines whether or not to perform pressure difference control for limiting decreases in the pressure difference of the outdoor unit based on whether or not the temperature of water flowing into the outdoor unit is less than the set lower limit value.