1: There is ice in the refrigerator. As long as the system has a little cooling capacity, it can maintain the previous non-icing. In fact, the refrigeration was already poor at that time, but the user thought there was ice. 2. There is insufficient refrigerant leakage in the system, so it is difficult to add normal frost after the previous ice melts. 3. The system leaks at low pressure. After a long power outage, the refrigerant leakage increases rapidly due to the rising of the high and low pressure balance.