Do you know the troubleshooting of high-pressure faults and oil leakage in chiller units?

There are two types of air conditioning units: refrigeration units and water-cooled units. The fan refers to the direct exchange of fresh air for cooling or heating, while the water machine refers to the cooling or heating of the heat medium water first sent to the fan coil air conditioning system, where the fresh air or mixed air is used to deliver heat or cold energy to the designated area at the end.
Chiller units, also known as freezers, refrigeration units, ice water units, cooling equipment, etc., have different requirements due to their widespread use in various industries. The chiller unit consists of four main components: compressor, evaporator, condenser, and expansion valve, thereby achieving the cooling and heating effects of the unit.
The high-pressure fault of the chiller refers to the high discharge pressure of the compressor, which causes the high-pressure protection relay to operate. The discharge pressure of the compressor reflects the condensation pressure, and the normal value should be between 1.4 and 1.8 MPa. It is recommended that the protection value should not exceed 2.0 MPa. Due to long-term high pressure, it can cause excessive operating current of the compressor, which can easily burn the motor and cause damage to the compressor.
1、 What are the main causes of high-voltage faults?
1. Excessive refrigerant charging. This situation usually occurs after maintenance, manifested as high suction and exhaust pressure, balance pressure, and high operating current of the compressor.
Solution: The refrigerant should be discharged under rated operating conditions based on the suction and exhaust pressure, equilibrium pressure, and operating current until normal.
2. The cooling water temperature is too high and the condensation effect is poor. The rated operating condition of the cooling water required by the chiller unit is between 30~35 ℃. High water temperature and poor heat dissipation will inevitably lead to high condensation pressure, which often occurs during high temperature seasons.
Solution: The cause of high water temperature may be a cooling tower malfunction, such as the fan not turning on or even reversing, the water distributor not turning, resulting in high and rapidly increasing cooling water temperature; The external temperature is high, the waterway is short, and the amount of recyclable water is small. In this situation, the cooling water temperature is generally maintained at a high level, and the solution can be to increase the water storage tank.
3. The cooling water flow rate is insufficient and cannot reach the rated water flow rate. The main manifestation is that the pressure difference between the inlet and outlet of the unit decreases (compared to the pressure difference at the beginning of the system's operation), and the temperature difference increases.
Solution: If the pipeline filter is clogged or too fine, the permeability is limited. Suitable filters should be selected and the filter screen should be cleaned regularly; Or choose a smaller water pump that is not compatible with the system.
4. The condenser is scaled or blocked. Condensed water is generally made from tap water, which is prone to scaling at temperatures above 30 ℃. Additionally, due to the open design of the cooling tower and direct exposure to air, dust and foreign objects can easily enter the cooling water system, causing blockages in the condenser, small heat exchange area, low efficiency, and affecting water flow rate. Its manifestation is that the pressure and temperature difference between the inlet and outlet water of the unit increase, and the temperature of the condenser is very high when touched by hand, causing the outlet copper pipe of the condenser to be hot.
Solution: Regularly backwash the unit and perform chemical cleaning and descaling if necessary.
5. False alarms caused by electrical faults. Due to moisture, poor contact, or damage to high-voltage protection relays, as well as moisture or damage to unit electronic boards, communication failures can cause false alarms.
Solution: This type of false fault often causes the fault indicator light on the electronic board to not light up or light up slightly, the manual reset of the high-voltage protection relay to be ineffective, the compressor's operating current to be normal, and the suction and exhaust pressures to be normal.
6. The refrigerant contains non condensable gases such as air and nitrogen. The refrigeration system has air, and often when there is a lot of air, the high pressure gauge pointer will shake violently.
Solution: This situation usually occurs after maintenance when the vacuum is not completely evacuated. After shutdown, the highest point of the condenser can be emptied or vacuumed again to add refrigerant.
Oil leakage treatment of chiller unit:
A: The oil is inside the evaporator. At this time, pay close attention to the temperature of the chilled water. You can reduce its flow properly to reduce the water temperature of the outlet water, and then quickly increase the flow to rapidly increase the temperature of the outlet water of the evaporator. At this time, the water temperature will be much higher than the saturation temperature of the refrigerant, so that the refrigerant will boil violently, and the cold frozen oil will be sucked into the compressor with the rolling refrigerant foam. At this time, the exhaust temperature should drop a little, but it should also be much higher than the separation temperature of oil and refrigerant, so that the oil will be returned to the oil separator and separated. Repeat several times, and the oil will be fully collected into the oil separator. Pay attention to the time interval for adjusting the water volume each time, and it is best to make the exhaust temperature rise back to the optimal level before each adjustment.
B: The oil is inside the condenser. At this point, there is no need to pay too much attention to the water temperature, as long as the unit can operate normally, there will be no major problems. At this time, the expansion valve should be gradually opened to the maximum (the opening process is not too fast to prevent the copper tube in the evaporator from being damaged by too much liquid supply), and wait for a few minutes until the high and low pressure of the unit are balanced. At this time, a large amount of white foam can be seen from the liquid sight glass of the evaporator, which means that the oil has entered the evaporator from the condenser. As long as step A is repeated, the oil will be quickly recovered.