With the development of technology, the field of use of refrigerators for freezing and refrigeration in the production, storage, and distribution of pharmaceuticals or food has increased. A refrigerator capable of maintaining an appropriate temperature is an important factor for safe medicine and food, and consumers are demanding safe medicine and food. In line with this, the standards of the Food Safety Management Certification Standard (HACCP) are being strengthened, and the HACCP certification is immediately revoked if the management standards of important management facilities are deviated from the implementation of the One-Strikeout System in 2015.
However, the rise in summer temperatures caused by climate change is becoming a harsh environment for the operation of air-cooled refrigerators. Refrigerators manufactured based on the past are causing many problems in recent summer operation, and replacing all old refrigerators is costly and time-consuming, and it is inevitable that it will take a long time.
The refrigerator that mainly uses air cooling is a small refrigerator, and since Willis Carrier patented it in 1906, only basic performance has been used to the extent that there has been no technological advancement. There has been progress to the extent of using PLC (Programmable Logic Controller) or DDC (Direct Digital Controller) for control, but the elements that constitute the control have not changed. This means that the PLC, which can utilize various functions using functions, is not being properly utilized, and operation and inspection are underway in a classical way that is classic.
It is very difficult to check the condition of the refrigerator only with limited pressure and temperature without special measuring equipment, and it requires high skill level. Inspection and repair in the actual field rely only on the experience and knowledge of the worker, and unskilled people feel great difficulty in inspection and repair. Delay of inspection and maintenance time is a factor that can cause problems in the safety of medicines and food, and incorrect inspection has adverse effects on the earth, such as global warming caused by refrigerants. Therefore, a method for fault diagnosis using PLC is proposed.