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1. The suction temperature is too high
Insufficient or leaking refrigerant leads to a reduction in the amount of refrigerant involved in the cycle, a decrease in the heat absorption capacity within the evaporator, and an increase in the suction temperature.
Insufficient refrigerant in the evaporator may be due to uneven system distribution or faults in the evaporator itself, which can affect the normal evaporation and heat absorption process of the refrigerant.
The expansion valve opening is too small, which restricts the flow of the refrigerant. Insufficient refrigerant enters the evaporator and cannot fully absorb heat, resulting in an excessively high suction temperature.
The suction pressure is too high
Excessive refrigerant, with too much refrigerant in the system, causes the pressure on the suction side of the compressor to rise.
Excessive heat load means that too much heat needs to be cooled in the cold storage, exceeding the refrigeration capacity of the refrigeration system, which leads to an increase in the suction pressure.
Improper opening of the expansion valve may cause it to open too wide, resulting in excessive refrigerant flow and an increase in suction pressure.
The temperature sensing bulb is not installed firmly and cannot accurately sense the temperature changes, which affects the normal adjustment of the expansion valve and leads to abnormal suction pressure.
When the displacement of the compressor decreases, if there is an internal fault in the compressor, causing its suction capacity to decline, it may indirectly lead to changes in the suction pressure (logically, a reduction in the displacement of the compressor usually results in a decrease in the suction pressure, but if combined with other system factors, such as improper adjustment of the expansion valve, etc., the suction pressure may also be relatively too high, and a comprehensive judgment is needed).
The oil separator fails to return oil properly, preventing the lubricating oil in the compressor from flowing back normally. This may affect the working condition of the compressor and further impact the suction pressure.
The suction pressure is too low
Insufficient refrigerant leads to a small amount of refrigerant in the system, and the suction pressure naturally decreases.
Ice plug: In the refrigeration system, water freezes after the expansion valve throttles, blocking the passage and affecting the flow of the refrigerant, resulting in a decrease in the suction pressure.
If the evaporator is too thick with frost, clogged with dirt or contains too much oil, it hinders the heat exchange between the refrigerant and the air, reduces the refrigeration efficiency of the evaporator and lowers the suction pressure.
The opening degree of the expansion valve is too small, which limits the flow of the refrigerant, and the suction pressure decreases accordingly.
The temperature sensing bulb leaked, and the expansion valve failed to adjust normally according to the temperature changes, resulting in abnormal refrigerant flow and a decrease in suction pressure.
The opening degree of the valve on the oil supply pipe and the liquid outlet valve is small, which restricts the supply of refrigerant and causes the suction pressure to drop.
The solenoid valve malfunctioned and failed to open or close normally, affecting the flow of the refrigerant and causing abnormal suction pressure.
The filter was clogged, hindering the flow of the refrigerant and causing a decrease in the suction pressure.
The exhaust temperature is too high
The load is heavy, and too much heat needs to be cooled in the cold storage. The compressor has to consume more energy to compress the refrigerant, resulting in an increase in the exhaust temperature.
The clearance volume is too large, and the clearance between the compressor piston and the cylinder is too large. During the compression process, some gas will remain, resulting in a decrease in compression efficiency and an increase in exhaust temperature.
The exhaust valve plate and gasket are damaged and gas leakage occurs, causing high-pressure gas to leak to the low-pressure side and resulting in an increase in exhaust temperature.
The suction superheat is large, the temperature of the refrigerant gas entering the compressor is too high, and the exhaust temperature is even higher after compression.
The temperature in Row 5 is too low
The compressor sucks in liquid. The liquid is incompressible. Once it enters the compressor, it will cause abnormal compression process and a decrease in exhaust temperature.
The expansion valve supplies too much liquid. Excessive liquid refrigerant enters the evaporator and is sucked into the compressor before it is completely evaporated, causing the exhaust temperature to drop.
The cooling load is insufficient, and the cooling capacity provided by the refrigeration system exceeds the actual demand of the cold storage, resulting in a decrease in exhaust temperature.
The frost on the evaporator is too thick, which affects the heat exchange efficiency of the evaporator, causing incomplete evaporation of the refrigerant. Some of the liquid refrigerant is drawn into the compressor, resulting in a decrease in the exhaust temperature.
The exhaust pressure is too high
The main issue lies with the condenser. For instance, if there is non-condensable gas in the system, it will occupy part of the condenser's space, reducing its heat exchange efficiency and causing the exhaust pressure to rise.
The air volume of the condenser fan is insufficient to remove the heat in the condenser in time, causing the condensing pressure to rise and subsequently leading to an excessively high exhaust pressure.
7. The exhaust pressure is too low
Insufficient refrigerant or leakage, the amount of refrigerant in the system is small, the condensing pressure drops, and the exhaust pressure also decreases accordingly.
The exhaust valve is leaking, and high-pressure gas is leaking, causing the exhaust pressure to drop.
Excessive cooling water volume, low water temperature, and improper energy regulation cause the refrigerant in the condenser to condense too quickly, resulting in a decrease in condensing pressure and a drop in exhaust pressure.
8. Liquid Strike
When starting with liquid, there is too much foam. When the compressor starts, a large amount of liquid refrigerant and lubricating oil mix to form foam, which is sucked into the compressor, causing liquid hammer.
There is too much lubricating oil in the compressor. Excessive lubricating oil may participate in the circulation, mix with the refrigerant and form a liquid mixture, which enters the compressor and causes liquid hammer.
If too much refrigerant is added and the refrigerant in the system is excessive, liquid hammer may occur during the start-up or operation of the compressor.
Evaporator failure or defrosting issue causes the evaporator to fail to evaporate the refrigerant normally, resulting in liquid refrigerant entering the compressor.
The volume design and selection of the gas-liquid separator are unreasonable, which cannot effectively separate the gas and liquid phases, allowing the liquid refrigerant to enter the compressor.
Refrigerant migration: After the compressor stops, the refrigerant migrates towards the compressor. When it is restarted, it may cause liquid hammer.
The oil pressure is too low
The oil quantity is insufficient. There is not enough lubricating oil in the compressor, and it cannot form sufficient oil pressure.
Improper adjustment, malfunction of the oil pressure regulating device or unreasonable setting result in excessively low oil pressure.
The oil filter is clogged or the oil inlet is blocked, which hinders the flow of lubricating oil and causes the oil pressure to drop.
The oil pump is worn out, and its oil pumping capacity decreases, unable to provide sufficient oil pressure.
Vacuum operation: The compressor operates under vacuum conditions, and the lubricating oil cannot circulate normally, resulting in excessively low oil pressure.
The motor is overheating.
Low voltage leads to high current, increasing copper and iron losses in the motor and causing it to heat up.
Poor lubrication leads to insufficient lubrication of components such as the motor bearings, increased friction, and excessive heat generation.
Overload operation causes the motor to bear a load exceeding its rated load, resulting in overheating of the motor.
There is non-condensable gas in the system, which affects the normal operation of the refrigeration system, increases the load on the motor and causes overheating.
Insulation damage of the electric winding, short circuit or grounding between the windings, generating additional current and heat, causes the motor to overheat.
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