by admin admin

During using cold room, there will  be some common faults for the refrigeration system, let us check and solve them.

  1. Refrigerant leakage:

Fault Analysis: After the refrigerant leaking in the system, the cooling capacity is insufficient, the suction and exhaust pressures are low, and the expansion valve can hear the intermittent airflow sound much larger than usual. The evaporator does not hang frost or hang a small amount of floating frost. If adjusting the expansion valve hole, the suction pressure does not change much. After shutdown, the equilibrium pressure in the system is generally lower than the saturation pressure corresponding to the same ambient temperature.

Solution: After the refrigerant leaking, don’t rush to fill the system with refrigerant. Instead, should find the leak point immediately, and fill the refrigerant after repair.

  1. Filling too much refrigerant after maintenance:

Fault Analysis: The amount of refrigerant charged in the refrigeration system after maintenance exceeds the normal volume of the system. The refrigerant will take up a certain volume of the condenser, reduce the heat dissipation area, reduce the cooling efficiency, and generally have high suction and discharge pressures. The evaporators don’t frost and the temperature cooling  is slow.

Solution: According to the operating procedure, it is necessary to stop the machine for a few minutes and then release excess refrigerant at the high pressure shut-off valve. At this time, the residual air in the system can also be released together.

  1. Air in the refrigeration system:

Fault Analysis: If there is air in the refrigeration system will reduce the cooling efficiency. The prominent phenomenon is that the suction and exhaust pressures increase (but the exhaust pressure has not exceeded the rated value), and the temperature at the compressor outlet to the condenser inlet is significantly increased. Due to the air in the system, the exhaust pressure and exhaust temperature increase.

Solution: It is possible to release air from the high pressure shut-off valve several times after a few minutes after the shutdown, and it is also possible to properly fill some refrigerant according to the actual situation.

4. The efficiency of compressor is low:

Fault Analysis: The low efficiency of the refrigeration compressor means that the actual exhaust gas volume decreases and the cooling capacity responds less when the operating conditions are constant. This phenomenon occurs mostly on compressors that have been used for a long time, and the wear is large, the clearance of each component is large, and the sealing performance of the gas valve is lowered to cause the actual exhaust gas to decrease.


(1) Check if the cylinder head paper pad is broken down and cause leakage. If it is, replace it.

(2) Check if the high and low pressure exhaust valves are not closed tightly, If it is, replace it.

(3) Check the clearance between the piston and the cylinder. If it is too large, replace it.


  1. The frost on the surface of the evaporator is too thick:

Fault analysis: Long-term use of the cold room evaporator should be timed defrosting, such as no defrosting, the frost layer on the evaporator line is thicker and thicker, when the whole pipeline is wrapped into a transparent ice layer, it will seriously affect heat transfer. Causes the cold room inside temperature can’t reach to required value.


Stop the defrosting, open the cold room door to let the air circulate, and use the fan to accelerate the air circulation and reduce the defrosting time.

  1. Refrigerantoil in the evaporator line:

Fault Analysis: During the cooling cycle, some of the refrigerant oil remains in the evaporator line. After a long period of use, when there is more residual oil in the evaporator, the heat transfer effect will be seriously affected, and the cooling efficiency will decrease.

Solution: Remove the refrigerant oil from the evaporator. Remove the evaporator, cleaned and then dried. If it is not easy to remove, it can be pumped from the evaporator inlet and then blown with a blowtorch.

  1. The refrigerant leakage in the temperature sensor of the expansion valve:

Fault analysis: After the refrigerant leaking in the temperature sensor of the expansion valve, the two forces below the diaphragm push the diaphragm up, the valve hole is closed, the refrigerant in the system can not pass, and the expansion valve doesn’t frost, the low pressure is vacuum, and no sound is heard in the evaporator.

Solution: Shut down the shut-off valve and remove the expansion valve to check if the filter is clogged  and replaced when damaged.

  1. The compressor suddenly stopped during operation

For air-cooled condenser:

Fault Analysis

1 The fan is not turned on.

2 The fan motor is damaged.

3 The fan is reversed.

4 The ambient temperature is high (up to 40 °C).

5 The condenser fins are blocked by oil dust and the air does not circulate.

For water-cooled condenser:

1 The cooling water valve is not open or opened too small, the inlet pressure is too low

2 The water volume control valve is broken.

3 The scale inside the condenser is thickness.

Solution: Clean the condensers timely.