1. The cooling capacity of the cold storage compressor decreases
2. The evaporation pressure is not suitable
3. Insufficient liquid supply to the evaporator
4. The frost layer on the evaporator is too thick
If your cold storage time is long, there may be the following reasons:
5. The evaporator contains excessive refrigeration oil
6. The ratio of cold storage area to evaporation area is too small
7. The cold storage insulation layer is damaged
Secondly: The cooling capacity of the cold storage compressor decreases
1. High condensation pressure
In summer (three months from July to August), the best condensation pressure is 11~12 kg, usually about 13 kg, and the worst is more than 14 kg.
The method to judge the high condensation pressure is to judge the pressure according to the inlet water temperature of the condenser (there is an error, the pressure is the gauge pressure)
The lower the evaporation pressure, the lower the cooling capacity of the refrigeration compressor. If the evaporation pressure is high, the cold storage cannot drop to the required temperature.
The evaporation pressure is low, the cooling capacity is reduced, and the temperature drops slowly or even not at all.
Next, the problem of the refrigeration compressor itself
The main problem of refrigeration compressor is high and low pressure gas cross-flow. The test method is
When the refrigeration compressor is operating normally, first close the suction valve, wait until the oil pressure decreases and the alarm sounds (20~30 seconds), then stop.
Close the exhaust valve. Observe the time required for the pressure balance between exhaust and suction. 15 minutes indicates serious air leakage and should be repaired.
30 minutes to 1 hour is normal gas flow
The worst machine balancing time I’ve seen is within 1 minute, and the best time is 24 hours.
The condensing pressure is generally between the highest and the lowest, depending on the system. The maximum pressure has an error of 0.5 kg.
If the actual pressure exceeds the maximum pressure by a large amount, the cause (such as air) should be found.
High condensation pressure, small investment, large operating costs, and low maintenance costs
Low condensation pressure, large investment, low operating costs, and high maintenance costs
Again the evaporation pressure is too low
The above relationship is the state when the cooling coefficient is maximum,
Note: The evaporation pressure refers to the pressure gauge on the return air regulating station, which is different from the suction pressure of the compressor.
The small difference is almost non-existent, and the big difference is 0.3 kg (the biggest difference I have ever seen).
If the actual evaporation pressure is lower than the minimum pressure corresponding to the temperature, the cooling capacity will be reduced.
The reasons range from slow cooling to no cooling at all. The reasons are as follows: 1. The frost layer on the evaporator is too thick, 2. There is oil in the evaporator, 3. The evaporator has low liquid supply,
2. The refrigerator is too large, and 5. the area ratio is wrong. .
3. Insufficient liquid supply to the evaporator
Common symptoms of insufficient fluid supply
The suction temperature of the refrigeration compressor is high, the suction valve is not frosted, the suction pressure is low, and the evaporator frosts unevenly.
4. Float automatic control instrument
This method is the most accurate, but the failure rate is extremely high
To repair this kind of fault, you need to know both electricity and refrigeration, and there are not many people like this.
Therefore, most manufacturers discard the float automatic control system after it is damaged.
5. The frost layer on the evaporator is too thick
Because the frost layer on the evaporator is too thick, it will affect the heat transfer coefficient and air circulation of the exhaust pipe, and reduce the evaporation pressure.
Therefore, evaporator frost should be removed frequently, the less the better. In actual application, you can refer to the following data
Defrost when the frost layer distance between the two tubes in the top row is less than 2 cm.
Defrost when the frost layer between the fins of the air cooler is less than 0.5 cm.
Guangxi Cooler Refrigeration Equipment Co.,Ltd.
Tel/Whatsapp:+8613367611012
Email：karen@coolerfreezerunit.com
Post time: Jan-29-2024