Currently on the market there are many units are constructed in accordance with the following ideas: frozen oil mixed with refrigerant oil separator, use the unit oil and refrigerant separation, then the refrigerant through the flooded evaporator to compressor. This model has good refrigerating effect, promotion is relatively large, but there is a problem in the operation, it is easy to "run oil", namely when the cooling water temperature is low, exhaust heat is not high, thereby separating oil from refrigerant mixture into the heat exchanger is not complete, resulted in the low pressure unit is low, even lead to blockage caused by the unit can not start the expansion valve.
The failure phenomena are as follows:
1, the oil separator inside can not see any traces of oil, this oil did not converge in the condenser, but through the expansion valve into the evaporator, the oil will stick to the evaporator heat transfer tube, the evaporator evaporation effect is not good, resulting in the low pressure evaporator, the compressor suction superheat is low and direct inhalation of liquid refrigerant, and when the compressor exhaust temperature is low, oil and refrigerant still can not be separated, so the vicious spiral will make all the oil pool in the evaporator, the compressor oil supply shortage because of loud noise, even the unit level alarm and shut down the oil separator.
2, the oil separator inside can not see any traces of oil, all the oil with the exhaust to the condenser, if the temperature remained low, then all the oil can be collected to the condenser, the expansion valve and the oil plug, the evaporator liquid supply due to insufficient pressure began to decrease, until the low pressure alarm stop.
The above is the so-called oil run phenomenon. The main reason is that the temperature of the chilled water is low and the exhaust temperature is low.
In the boot process encountered such problems solution is as follows:
1, when the oil level in the lower part, the unit will immediately transferred to the manual control mode, limit the compressor load, such as the energy restriction in 50%.
2. Increase the condensing pressure.
3, the unit low pressure alarm value and low voltage shutdown value is reduced to the allowable range, as far as possible to ensure that the unit can be in the running state.
4, if the oil level is still very low, and the pressure in the evaporator is also very low, we must consider whether the oil is running into the evaporator. See if there is a large amount of white foam rolling in the liquid mirror of the evaporator. If there is, it indicates that the oil is in the evaporator, otherwise it may be in the condenser.
5, with the above steps, after half an hour or so, the cooling water temperature and exhaust temperature should rise to normal, below the beginning of oil collection:
A: the oil is in the evaporator. At this time to pay close attention to the chilled water temperature, can be appropriate to reduce the flow, let the water temperature decrease, then increase the evaporator water flow, the temperature rises rapidly, then the temperature will exceed the saturation temperature of the refrigerant, so the refrigerant seething, frozen oil will be bubbling as the refrigerant suction compressor when the exhaust temperature should be reduced, but also should be far more than the separation of oil and refrigerant temperature, thus the oil back to the oil separator and make them separate. Repeated several times, the oil will be returned to the oil separator. Attention is paid to the time interval for each adjustment of water quantity. It is best to adjust the exhaust temperature to the optimum before each adjustment.
B: the oil is in the condenser. You don't need to pay too much attention to the water temperature. As long as the unit can work properly, there will be no big problem. At this time should be gradually opened to the maximum expansion valve (opening process not too fast, to prevent the liquid supply too much damage in the evaporator tubes), wait a few minutes, until the unit high pressure balance, then you can see a lot of white foam from the evaporator liquid mirror, which is already in the oil from the condenser into the in the evaporator. As long as you repeat the A step, the oil will soon come back.
