Pre-Inspection Preparation
Before inspecting an evaporator, clarify the operating status with relevant personnel including whether the storage temperature is stable, the cooling speed is normal, the defrosting effect meets standards, and whether there are abnormal noises during operation. Check the control panel to record key data including suction pressure, exhaust pressure, and current value as a baseline. Power off the unit and hang warning signs. Wait for the evaporator fan to come to a complete stop before performing operations, and wear protective clothing for low-temperature environment work.
Five Core Inspection Points
First, check frosting condition. Normal frosting is uniform, loose, and similar to a thin layer of snow. Ice shell formation indicates incomplete defrosting, uneven frost distribution indicates uneven refrigerant distribution or partial blockage, and no frost indicates refrigerant leakage or severe shortage. Second, listen to operating sounds. Normal fan sound is a steady low humming. Clicking sounds indicate deformed blades or worn bearings, while excessive whooshing indicates dust accumulation. Normal refrigerant flow produces a uniform hissing sound. Third, measure temperature distribution using an infrared thermometer. The normal temperature difference between the refrigerant inlet and outlet is 8 to 12 degrees, and the difference between branch liquid distribution pipes should not exceed 2 degrees. Fourth, check the drainage system as drainage faults account for over 30 percent of all evaporator faults. The pipe must have a slope of at least 1 percent with no U-shaped bends. Fifth, check electrical connections including fan motor insulation resistance, defrost heating tube resistance, and temperature sensor accuracy.
Common Fault: Severe Evaporator Icing
Root causes include insufficient defrosting time or too long defrosting interval, damaged defrost heating tubes, defrost sensor failure, and poor cold storage door sealing allowing continuous moist air entry. Troubleshoot by first manually de-icing with warm water or special de-icing equipment, then adjust defrosting settings to increase frequency or extend time. Test the resistance of defrost heating tubes and replace damaged ones. Calibrate the defrost sensor and check door sealing strips for damage.
Common Fault: Slow Cooling Speed
This may be caused by dirt blockage on the evaporator surface reducing heat exchange efficiency, insufficient air volume from fan failure or dust accumulation, insufficient refrigerant in the system, or improper expansion valve adjustment. Clean the evaporator using a special cleaning agent while protecting electrical components. Check and clean fan blades and inspect bearing status. Perform pressure testing to find and repair refrigerant leaks, then recharge to standard amount. Adjust the expansion valve in small increments and observe the cooling effect after each adjustment.
Recommended Inspection Frequency
For low-temperature storage at minus 18 degrees or below, perform daily inspection with monthly deep inspection due to fast frosting and frequent defrosting. For high-temperature storage between 0 and 5 degrees, inspect weekly with quarterly deep inspection. For quick-freezing storage, perform daily inspection with bi-weekly deep inspection due to high load and fast component wear. Daily inspection requires only visual and auditory checks, while deep inspection must record all data including frosting condition, temperature distribution, electrical parameters, and drainage status.
