Water Chiller Troubleshooting
The water chiller is a water cooling equipment, which can provide constant temperature, constant current and constant pressure. The principle of the water chiller is that a certain amount of water is injected into internal water tank, making refrigerating system cools the water, and then water pump inside the machine injects cryogenic freezing water into an equipment which needs to cool back. The frozen water takes away calories inside the machine, then high temperature water backflow in water tank cools down. Cycle alternation cool reaches a function that cools equipment.
In order to ensure the safety, efficient and economical long-term normal operation of the water chiller, it is very important to discover hidden troubles as early as possible during its use.
The temperature difference between inlet and outlet water of water chiller is too small
1. The output of the chiller is small. For example, water chiller is malfunctioning or not fully loaded, which can be determined initially by observing electric current and other parameters in the process of water chiller.
2. Because the heat transfer effect is not good. For example, heat transfer tube produces serious dirt, which affects the heat exchange of the water chiller. It can be judged by observing heat transfer temperature difference between the water temperature and the evaporation temperature.
3. Water flow is excessive, which can be judged by observing the water pressure difference between the inlet and outlet water of the evaporator and the pump current.
4. After excluding the above problems, it must be taken into consideration whether the sensor or thermometer is accurate.
In addition, some appearances of the water chiller need to pay attention. For example, the suction tube of air compressor appears frost, showing excessive cooling capacity of water chiller, too low evaporation temperature, too small air compressor suction heat, and low air pressure. This will cause liquid strike for piston water chiller and it will cause surge of centrifugal chiller.
Water chiller noise
1. The blade generates friction or impact on air when it rotates. The frequency of noise is composed of multiple frequencies which are all related to the speed of the fan. The suggestion is that if the axial fan has the configuration of moving wing and static wing, the quantity of blades of the two is better different to avoid the bigger noise resonance.
2. When the blade generates vortex, noise is made. During the operation of the fan, the back of the moving wings generates vortex, which reduces fan efficiency and makes noise. To reduce this phenomenon, the installation angle of the blade should not be too large, the blade bending should be smooth, and it should not be changed suddenly.
3. Resonate with the air duct shell and generates noise. The joint between the inner surface of the air duct and the fan casing should be smooth to avoid roughness and unevenness, causing tearing sound. In addition, in order to reduce noise, sometimes the wind pipes can be covered with soundproof material.
Expect fixed noise of the fan itself, there are many other noises. For example, bearing generates noise because of insufficient precision, impropriate assembly or poor maintenance.
Low voltage failure
The compressor has low inspiratory pressure, causing low-pressure protection relay to operate. The compressor suction pressure reflects the evaporation pressure, and the normal value should be 0.4~0.6MPa, the protection value is set to 0.2MPa. The lower suction pressure, the lesser return air volume, which causes insufficient cooling capacity and a waste of electrical energy. it is easy to damage motor for poor heat dissipation of compressor motor with return air cooling.
The causes of low voltage failure is as follows:
1. Insufficient refrigerant or leakage. If the refrigerant is insufficient and partial leakage, the equilibrium pressure may be high when it is out of service. The suction pressure and the exhaust pressure are low after starting up, with small compressor operating current. And the short running time reports a low pressure failure. The computer displays “LPCURRENT“, and LP faults indicator of the unit electronic board is on. The computer displays “LPRESET” after a few seconds, and then the LP faults indicator of the unit electronic board is off. If the refrigerant most leaks, it will cause the low equilibrium pressure. And a low-pressure fault is reported when the water chiller is turned on. If the suction pressure is less than 0.2MPa, it can’t to be turned on. And the computer displays “LPCURRENT“, and LP fault indicator of unit electronic board is on. Furthermore, there is also a possibility that the refrigerant is sufficient, but the expansion valve opening is too small or blocked (or refrigerant piping line is not smooth), which causes the low voltage fault. This situation usually tends to high equilibrium pressure, but suction pressure is very low during operation, exhaust pressure is high, the compressor operating current is large. The expansion valve frosts with low temperature value. It takes a long time for the pressure to return to equilibrium after shutdown. The expansion valve is frost, and the pressure can be restored to equilibrium a long time after shutdown. This situation generally occurs to low-temperature operation or at the beginning of each year, and can return to normal after a period of operation.
2. The refrigerant water flow is insufficient, absorbing seldom calories with bad refrigerant evaporation effect. Moreover, the super cooled and supersaturated steam is easy to produce wet compression, which shows that the pressure difference between the water inlet and outlet of chiller becomes smaller, the temperature difference becomes larger. And low suction temperature makes frost on the suction port.
The causes of insufficient refrigerant water flow are as follows:
- There is air or water shortage of the system. The solution is to install an exhaust valve at a high place for exhausting.
- The pipeline filter is clogged or selected too thin, which the permeability is limited. Therefore, a suitable filter should be selected and regularly clean the filter.
- The pump is selected to be smaller and not compatible with the system. The larger pump should be selected, or the backup pump should be enabled.
3. The evaporator is blocked, causing poor heat transfer and then the refrigerant can’t be evaporated. The harm is the same like water shortage, but the difference is that the pressure difference between inlet and outlet becomes larger, and the suction port appears frost. Therefore, the water chiller should be cleared repeatedly and regularly.
4. False alarm caused by electrical failure of water chiller. The low-voltage protection relay is wetted, short-circuited and poorly contacted or damaged, which causes the unit electronic board is wetted or damaged. And the communication failure brings about a false alarm.
5. In a low outside environment, low voltage fault is caused by starting up operation when the cooling water temperature is very low. There some measures can be taken to increase the cooling water temperature, such as shutting the cooling tower and throttling the cooling water. When the chiller is running, because there is not enough preheating, the temperature of the refrigeration oil is low, and the refrigerant is not fully separated, that will occur a low voltage fault. In order to back onto normal, preheating time should be extended to make the refrigerating oil temperature rises.
High voltage failure
The compressor has high exhaust pressure, causing high-pressure protection relay to operate. The compressor exhaust pressure reflects the condensing pressure, and the normal value should be 1.4~1.6MPa, the protection value is set to 2.0MPa. The higher long-term pressure, the bigger operating current, which is easy to burn motor and also damage to compressor exhausted valve.
The causes of high voltage failure is as follows:
1. The cooling water temperature is too high and the condensation effect is poor. The rated working condition of the cooling water required by the chiller is 30 ~ 35℃. The higher water temperature, the poorer heat dissipation, which is certainly cause of high condensing pressure. This phenomenon normally happens to warm season.
2. The cooling water flow is not enough to reach the rated water flow. It shows that the pressure difference between the chiller inlet and outlet water becomes smaller (compared with the pressure difference at the beginning of the system), and the temperature difference becomes larger. One of the reason is that there is air or water shortage of the system. In order to settle this problem, an exhaust valve should be installed at a high place in the pipeline to exhaust. Another reason is that the pipeline filter is clogged or selected too thin, which the permeability is limited. Therefore, a suitable filter should be selected and regularly clean the filter. The third reason are that the pump is selected to be smaller and not compatible with the system.
3. The condenser is fouled or clogged. Tap water is generally used for condensate, which is easy to produce dirt above 30℃. Because cooling tower is open and directly exposed to the air, dust and foreign objects can easily enter the cooling water system. And then the condenser is dirty, the heat exchange area is small, the efficiency is low, and the water flow is also affected. It shows that the pressure difference between the chiller inlet and outlet water and the temperature difference become larger. The temperature of the upper and lower sides of the condenser is very high, and the copper pipe of the condenser are hot. In order to settle this problem, the chiller should be washed regularly, and it is necessary to chemically descale.
4. Too much refrigerant charged. This situation usually occurs after maintenance. The performance is the suction and discharge pressure, the equilibrium pressure is higher, and the compressor operating current is also higher. At rated working conditions, it should be deflated according to suction and exhaust pressure, equilibrium pressure and compressor operating current until normal.
5. The refrigerant has non-condensing gas, such as air, nitrogen and so on. This situation usually occurs after maintenance, because of incomplete vacuuming. Therefore, it can only re-evacuated and recharged with refrigerant.
6. False alarm caused by electrical failure of water chiller. Because the high-voltage protection relay is wetted, short-circuited and poorly contacted or damaged, the unit electronic board is wetted or damaged. And the communication failure brings about a false alarm.