Causes and solutions of low pressure faults of chillers
2022-04-26
(1) Insufficient or leaking refrigerant. If the refrigerant is insufficient and only partially leaks, the balance pressure may be high during shutdown, and the suction pressure and exhaust pressure are lower after startup, the compressor running current is small, and the operating time is short, and a low pressure fault will be reported. The computer displays "LPCURRENT", and at the same time, the LP fault indicator of the unit electronic board is on. After a few seconds, the computer displays "LPRESET", and the LP fault indicator of the unit electronic board is off.
If most of the refrigerant leaks, the balance pressure is very low, and a low pressure fault is reported when the chiller is turned on. If the suction pressure is lower than 0.2MPa, it cannot be turned on, the computer displays "LPCURRENT", and the LP fault indicator on the unit electronic board is on. Another possibility is that there is enough refrigerant, but the expansion valve is too small or blocked (or the refrigerant pipeline is not smooth), which may also cause a low pressure failure. In this case, the balance pressure is often high, but the suction pressure is very low during operation, the discharge pressure is high, the compressor running current is also large, and the valve temperature is also low, the expansion valve is frosted, and the pressure is long after shutdown. to restore balance. This situation generally occurs in the low temperature period or the early operation of each year, and it can return to normal after running for a period of time.
(2) Insufficient flow of refrigerant water, less heat absorption, poor refrigerant evaporation effect, and supercooled and supersaturated steam, which is prone to wet compression, which is manifested in the smaller pressure difference between the inlet and outlet of the unit, the larger temperature difference, and the lower suction temperature. , There is frost on the suction port.
The reason for the insufficient water flow is: there is air or water shortage in the system, the solution is to install an exhaust valve at the height of the pipeline to exhaust; the pipeline filter is blocked or too thin, and the water permeability is limited, and a suitable filter should be selected. And clean the filter screen regularly; choose a small water pump, which is not matched with the system, should choose a larger water pump, or enable a backup water pump.
(3) The evaporator is blocked, the heat exchange is poor, and the refrigerant cannot evaporate. Backwash.
(4) The electrical fault of the chiller causes false alarms. False alarms caused by communication failure due to moisture short circuit, poor contact or damage to the low-voltage protection relay, moisture or damage to the unit electronic board.
(5) When the outside air temperature is low and the cooling water temperature is very low, a low pressure fault will also occur; when the unit is running, due to insufficient preheating, the temperature of the refrigeration oil is low, and the refrigerant is not sufficiently separated, and a low pressure fault will also occur. . For the former case, measures such as closing the cooling tower and throttling the cooling water can be taken to increase the cooling water temperature. In the latter case, the preheating time is extended, and the temperature of the refrigeration oil can generally return to normal after the temperature rises.
If most of the refrigerant leaks, the balance pressure is very low, and a low pressure fault is reported when the chiller is turned on. If the suction pressure is lower than 0.2MPa, it cannot be turned on, the computer displays "LPCURRENT", and the LP fault indicator on the unit electronic board is on. Another possibility is that there is enough refrigerant, but the expansion valve is too small or blocked (or the refrigerant pipeline is not smooth), which may also cause a low pressure failure. In this case, the balance pressure is often high, but the suction pressure is very low during operation, the discharge pressure is high, the compressor running current is also large, and the valve temperature is also low, the expansion valve is frosted, and the pressure is long after shutdown. to restore balance. This situation generally occurs in the low temperature period or the early operation of each year, and it can return to normal after running for a period of time.
(2) Insufficient flow of refrigerant water, less heat absorption, poor refrigerant evaporation effect, and supercooled and supersaturated steam, which is prone to wet compression, which is manifested in the smaller pressure difference between the inlet and outlet of the unit, the larger temperature difference, and the lower suction temperature. , There is frost on the suction port.
The reason for the insufficient water flow is: there is air or water shortage in the system, the solution is to install an exhaust valve at the height of the pipeline to exhaust; the pipeline filter is blocked or too thin, and the water permeability is limited, and a suitable filter should be selected. And clean the filter screen regularly; choose a small water pump, which is not matched with the system, should choose a larger water pump, or enable a backup water pump.
(3) The evaporator is blocked, the heat exchange is poor, and the refrigerant cannot evaporate. Backwash.
(4) The electrical fault of the chiller causes false alarms. False alarms caused by communication failure due to moisture short circuit, poor contact or damage to the low-voltage protection relay, moisture or damage to the unit electronic board.
(5) When the outside air temperature is low and the cooling water temperature is very low, a low pressure fault will also occur; when the unit is running, due to insufficient preheating, the temperature of the refrigeration oil is low, and the refrigerant is not sufficiently separated, and a low pressure fault will also occur. . For the former case, measures such as closing the cooling tower and throttling the cooling water can be taken to increase the cooling water temperature. In the latter case, the preheating time is extended, and the temperature of the refrigeration oil can generally return to normal after the temperature rises.
