Cooling system and controlling method thereof

A cooling system comprising:

• a plurality of cooling devices;
• and
• an outdoor unit configured to provide a refrigerant to each of the plurality of cooling devices,
• wherein each of the plurality of cooling devices comprises:
• an evaporator configured to exchange heat between the refrigerant and air;
• a communication unit comprising communication circuitry configured to communicate between the plurality of cooling devices;
• a user interface comprising circuitry configured to obtain an input;
• and
• a controller, comprising circuitry, electrically connected to the communication unit and the user interface and configured to set a defrosting group based on the input, and
• wherein based on any one of cooling devices belonging to the same defrosting group satisfying a specified defrosting entry condition, all of the cooling devices belonging to the same defrosting group are configured to enter a defrosting operation together.