Air conditioning system and control method thereof

A method for controlling an air conditioning system including:

• a plurality of indoor units installed in a same indoor space, the indoor units including respective usage-side heat exchangers and being capable of setting set temperatures individually, and
• an outdoor unit including a heat-source-side heat exchanger arranged and configured to conduct heat exchange with refrigerant circulating through the usage-side heat exchangers, the method comprising:
• a first step of causing temperature control of the same indoor space to be performed in each indoor unit, using a thermo-ON condition set in advance in accordance with the set temperatures;
• and
• a second step of relaxing the thermo-ON condition of thermo-OFF indoor units when the indoor units include both those that are thermo-ON and those that are thermo-OFF and a predetermined condition is satisfied,
• the predetermined condition being that at least one of the plurality of indoor units continues to be thermo-ON for a first elapsed time or longer, and at least one of the plurality of indoor units continues to be thermo-OFF for a second elapsed time or longer.