Why does the cold storage compressor freeze

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1、 Compressor return air frosting
Due to a small amount of refrigerant, the low evaporation pressure of the evaporator leads to a low evaporation temperature, which gradually leads to condensation in the evaporator to form an insulation layer and transfer the expansion point to the compressor return air, resulting in frost formation in the compressor return air. Both of the above points will show evaporator frost before the compressor return air frosts.
2、 Cylinder head frost (severe crankcase frost)
1. The opening of the thermal expansion valve is adjusted too large, causing the installation of the temperature sensing package to be incorrect or loose, resulting in an abnormally high temperature that causes the valve core to open abnormally.
2. The leakage of the supply solenoid valve or the lax closure of the expansion valve during shutdown can cause a large amount of refrigerant liquid to accumulate in the evaporator before startup. The temperature relay is used in conjunction with an electromagnetic valve to control the temperature of the warehouse.
3. When starting the compressor, the suction shut-off valve is opened too large or too early.
4. When there is too much refrigerant in the system, the liquid level in the condenser is high, and the condensation heat exchange area is reduced, resulting in an increase in condensation pressure. That is, the pressure in front of the expansion valve increases, and the amount of refrigerant flowing into the evaporator increases. Liquid refrigerant cannot completely evaporate in the evaporator, so the compressor absorbs wet steam, causing the cylinder head to cool or even frost, and may cause "liquid shock". At the same time, the evaporation pressure may also be too high.
Defrosting method:
In fact, in most cases, for the phenomenon of frost formation, just adjust the hot air bypass valve. The specific method is to open the rear end cover of the hot air bypass valve, and then use a No. 8 Allen wrench to turn the adjusting nut clockwise. The adjustment process should not be too fast, usually pausing for about half a turn. Let the system run for a period of time to see the frost formation before deciding whether to continue adjusting. After the operation is stable and the frost phenomenon of the compressor disappears, tighten the end cover.
For models below 15 cubic meters, due to the lack of a hot air bypass valve, if frost formation is severe, the starting pressure of the condensing fan pressure switch can be appropriately increased. The specific method is to first find the pressure switch, remove the adjusting nut of the pressure switch and fix the small piece, then use a cross screwdriver to rotate clockwise. The entire adjustment also needs to be slowly carried out, and adjust half a turn to see the situation before deciding whether to adjust.