A controller has a timer operation mode in which the operation of a refrigeration cycle that operates as a heat source or a cold source is started before a set operation start time of an indoor fan by a preliminary operation time period. In the timer operation mode, the controller calculates a heat capacity of water or brine, calculates a heat storage amount of a second heat medium from a temperature detected by a temperature sensor and the heat capacity, and determines the preliminary operation time period from the heat storage amount. By determining the preliminary operation time period in this manner, timer operation can be performed such that air at an appropriate temperature is blown from an indoor unit at the operation start time of the indoor fan, from the initial time at which an air conditioning apparatus is installed.