Air-conditioning apparatus with simultaneous heating and defrosting modes

An air-conditioning apparatus comprising:

• a plurality of outdoor units through which refrigerant flows, the plurality of outdoor units each including a compressor and an outdoor heat exchanger;
• at least one indoor unit through which a heat medium flows, the at least one indoor unit including an indoor heat exchanger;
• a plurality of relay devices to which the plurality of outdoor units are connected independently, and to which the indoor unit is connected, each of the plurality of relay devices including a heat medium heat exchanger configured to exchange heat between the refrigerant and the heat medium;
• and
• a controller configured to control action of the plurality of outdoor units, the indoor unit, and the plurality of relay devices,
• the controller being configured to
• determine the necessity for a defrosting operation for each of the plurality of outdoor units,
• responsive to determining that the defrosting operation is necessary, compare an indoor unit total load with an outdoor unit total capacity, the indoor unit total load indicating an air conditioning load during a heating operation, the outdoor unit total capacity indicating a capacity of an other outdoor unit excluding a target outdoor unit where the defrosting operation is necessary, and
• responsive to determining that the indoor unit total load is greater than the outdoor unit total capacity as a result of comparing, control an operating frequency of the compressor of the other outdoor unit to increase the outdoor unit total capacity.