Compressor overheating error and low valve temperature error.
Compressor overheating error
The thermistor is embedded in the compressor motor winding, and the resistance is generally 1kΩ. When the winding is overheated, the resistance value will increase rapidly. When it exceeds 141kΩ, the thermal protection module SSM will act to cut off the operation of the unit. At the same time, it will display an overheating fault and the TH fault indicator will be on.
The causes of compressor overheating failure are as follows:
(1) The compressor is overloaded and overcurrent runs. The possible reasons are: too high cooling water temperature, too much refrigerant charge, or non-condensable gas such as air in the refrigeration system, resulting in a large compressor load, manifested as overcurrent, and accompanied by high-voltage failure.
(2) Compressor overcurrent operation caused by electrical failure. If the three-phase power supply voltage is too low or the three-phase unbalanced, the current or the current of one phase is too large; the AC contactor is damaged and the contact is ablated, causing the contact current to be too large or the current to be too large due to the lack of phase.
(3) The overheating protection module SSM is damp or damaged, the intermediate relay is damaged, and the contact is bad. It is manifested as an overheating failure at startup, and the compressor cannot be started. If the electronic board of the unit fails or the communication fails, it may also falsely report an overheating failure.
7. Low valve temperature error
The temperature at the outlet of the expansion valve reflects the evaporation temperature and is a factor that affects heat transfer. Generally, the temperature difference between the outlet temperature of the expansion valve and the refrigerant water is 5 ~ 6 ℃. When a low valve temperature fault occurs, the compressor will stop, and when the valve temperature rises, it will automatically resume operation, with a protection value of -2 ℃.
The causes of low valve temperature failure are as follows:
(1) A small amount of refrigerant leakage, generally manifested as a low valve temperature failure rather than a low pressure failure. If the refrigerant is insufficient, it will evaporate at the outlet of the expansion valve, causing a temperature drop. The frost will appear at the outlet of the expansion valve. At the same time, the temperature of the suction port will be higher (superheated steam).
(2) The expansion valve is clogged or the opening degree is too small, and the system is not clean. If the refrigerant pipeline is not cleaned after maintenance, the refrigerant is impure or contains water.
(3) Insufficient refrigerant water flow or clogging of the evaporator, poor heat transfer causes low evaporation temperature and low suction temperature, and the opening of the expansion valve is adjusted according to the suction temperature, and the lower the temperature, the smaller the opening, resulting in Low valve temperature failure.
(4) False alarms caused by electrical faults, such as poor contact of valve temperature wires, cause the computer to display -5 ℃ unchanged.
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