1. Protection caused by temperature:
(1) The lack of refrigerant or the opening of the expansion valve is too small, the return air temperature is too high, resulting in the exhaust temperature exceeding the protection temperature, temperature protection (with low pressure).
(2) The return air temperature is too high. This causes the exhaust gas temperature to increase, leading to temperature protection (with low pressure).
(3) The expansion valve high temperature package is too close to the compressor. The temperature detected by the temperature sensor is larger than the actual temperature, which causes the expansion valve to open too much, the refrigerant evaporation is incomplete, and part of the liquid enters the compressor to cause liquid shock.
(4) The working condition of the condenser is relatively poor, the surface of the condenser is dirty (dust or oil) and the heat exchange cannot be performed normally, and the ambient temperature of the condenser is too high, which causes the heat to be exchanged and the condensation temperature rise , Condensation is reduced, and the pressure from the exhaust to the condenser pipe section is increased, resulting in excessive discharge pressure and temperature of the compressor (temperature protection).
(5) The compressor lacks oil or the motor bearing is damaged, the motor heat increases, and the heat cannot be dissipated in time, resulting in temperature protection.
(6) The type of refrigerant charging is not correct (different refrigerants, oil, heat exchanger matching, expansion valve matching, refrigerant charging amount, etc.).
2. Protection caused by stress:
(1) Too much refrigerant. Liquid strikes, compressor compression is difficult, and the load exceeds the standard, resulting in high pressure protection (the pressure does not necessarily increase during temperature protection, but the temperature rise must be accompanied by high temperature protection, because the motor heat generation increases).
(2) The pipeline is dirty. Such as filter clogging, capillary clogging, etc., leading to an increase in exhaust pressure, thus high-pressure protection.
(3) There is air in the pipeline. Compression is difficult, resulting in high-pressure protection.
(4) Low pressure is too low. Reasons: (1) There is too little refrigerant in the refrigeration system, (2) The indoor heat exchanger or filter is blocked, (3) The electronic expansion valve is too small to open, (4) The fan speed of the evaporating part is low or stopped ) The refrigeration system is semi-clogged (dirty plug, ice plug, oil plug).