Heat pump apparatus and control method for heat pump apparatus

A heat pump apparatus comprising:

• a heat source device that cools or heats a refrigerant;
• a first use device that cools a first fluid by utilizing the refrigerant cooled by the heat source device;
• a second use device that heats a second fluid by utilizing the refrigerant heated by the heat source device;
• and
• a controller that
• causes, when there is an operation request for one of the first use device and the second use device, even when there is no operation request for the other, both the one and the other to operate if the other satisfies a certain condition, and
• causes the first use device and the second use device to perform a waste heat recovery operation and in which the second use device heats the second fluid by utilizing a refrigerant heated by cooling the first fluid in the first use device, wherein
• the controller
• determines that there is an operation request for the second use device if a temperature of the second fluid is less than or equal to a first heating temperature set by a user, and
• when there is the operation request for one of the first use device and the second use device, and both the one and the other are to operate, operates the second use device such that the temperature of the second fluid becomes a second heating temperature that is set higher than the first heating temperature by a certain degrees.