Abstract: Defrosting system is the basic system to ensure the normal operation of the refrigeration system of frost free refrigerator. If the defrosting system fails, the refrigerator cannot cool normally. The design of defrosting fuse is the key link in the safety design of air-cooled refrigerator. The height of the evaporator of the single system pair door frost free refrigerator is about twice that of the ordinary air-cooled refrigerator, and the heat transfer distance is increased, so it is difficult to achieve reliable defrosting effect. From the market after-sales maintenance situation, the phenomenon of abnormal fusing of defrosting fuse in frost free refrigerator products is common in the industry. In order to solve the problem of defrosting system, several main fault causes of fuse abnormal fusing are determined through investigation and test analysis. The reliability method of fuse design: bidirectional balance method is proposed. That is, balance the two tests of residual test and dry and wet burning test to find the best design position. Ensure that the fuse of the refrigerator will not fuse abnormally under various environments. It provides an important reference method for design practitioners in the industry.

Key words: Frost free refrigerator, Defrosting heater, Fuse, Reliability design