In the design of a cold storage, the contactor of the compressor is interlocked with the defrosting heater contactor to ensure that the defrosting heating wire does not function during cooling or that the compressor does not work when defrosting. Although the microcomputer thermostat has independent control of the compressor and defrosting output, if it is disturbed or damaged, it may simultaneously output two signals of compressor cooling and defrosting, at which time the cold storage will simultaneously cool and defrost. Therefore, in order to be safe and reliable, the contactor of the compressor and the evaporator contactor are set to an interlock function, so that even if the microcomputer thermostat is disturbed or damaged, the compressor and the defrosting heating wire can be prevented from working at the same time.
The evaporator fan works in a low temperature and high relative humidity environment. If the installation is not good or the short circuit may occur under special circumstances, the current of the evaporator fan is very large, but the original circuit does not have an overload protection relay. Lead to an accident. It is therefore necessary to install an overload protection relay for the evaporator fan. If the evaporator fan fails and stops running, the compressor will not stop running, and the cooling will continue. The throttled refrigerant liquid absorbs heat in the evaporator, causing the evaporator temperature to decrease, but the storage temperature is increased. .
The control of the condensing fan is controlled separately from the compressor control, the condensing fan is installed with overload protection, and the compressor installation setting is delayed. The compressor and condenser fan in the original control circuit are controlled by the same contactor. However, since manual control is required to be added to the original cold storage automatic control, the two parts are separately controlled.
After the separation, the original overload protection relay can only protect the compressor and can not protect the condenser fan, so the condenser fan should be equipped with an overload protection relay. After separate control, in order to better demonstrate the operation of each device in the system, a delay start compressor is added after the condenser fan is running (the delay relay of the original compressor is used for the delay of the condenser fan).
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