Air-conditioning apparatus

An air-conditioning apparatus comprising:

• a heat medium loop;
• a refrigerant loop;
• a plurality of use side heat exchangers connected to the heat medium loop;
• a first heat exchanger that exchanges heat between heat medium and the refrigerant to heat the heat medium;
• a second heat exchanger that exchanges heat between the heat medium and the refrigerant to cool the heat medium;
• each use side heat exchanger associated with:
• a respective heat medium flow path switching device including a valve that switches between a flow path connecting said first heat exchanger to the respective use side heat exchangers and a flow path connecting said second heat exchanger thereto alternatively;
• a respective heat medium flow rate adjusting unit including a first valve and a second valve, said heat medium flow rate adjusting unit configured to control the flow rate of the heat medium flowing into the respective use side heat exchanger;
• a respective first heat medium temperature sensor that detects a temperature of the heat medium flowing out of the respective use side heat exchanger;
• the apparatus further includes a controller configured to control the heat medium flow path switching devices and the heat medium flow rate adjusting units;
• the controller configured to perform an operation including the following steps:
• first, detect when one of the use-side heat exchangers has 1) switched from an inactive state to an active state or 2) has switched from cooling mode to heating mode, or from heating mode to cooling mode;
• second, accordingly control the respective use-side heat exchanger's heat medium flow path switching device;
• third, detect whether another use-side heat exchanger is engaged in the same active operation mode as the respective use-side heat exchanger;
• if the answer to the third step is NO, then the controller adjusts the respective second valve on the basis of air conditioning load to the respective use-side heat exchanger,
• if the answer to the third step is YES, then the controller is configured to perform an operation including the following steps:
• first, the controller sets the respective first valve to a predetermined opening degree;
• second, the controller opens the respective second valve;
• third, the controller receives a temperature measurement from the respective first heat medium temperature sensor, if the temperature is less than or equal to a first threshold temperature, then the controller closes the respective first valve by a predetermined amount in order to suppress a temperature change in the heat medium;
• and
• fourth, the controller adjusts the respective second valve on the basis of air conditioning load at the respective use-side heat exchanger.