H. Low suction temperature
1. Too much refrigerant charge;
Occupying part of the volume of the condenser and increasing the condensing pressure, the liquid entering the evaporator will increase. The liquid in the evaporator can not be completely gas field, so that there are liquid micro drops in the gas sucked by the compressor. In this way, the temperature of the return pipe decreases, but the evaporation temperature does not change because the pressure does not decrease, and the super heat decreases. Even if the expansion valve is closed, there is no significant improvement.
2. The opening of expansion valve is too large.
Due to the loose binding of the temperature sensing element, the small contact area with the air return pipe, or the temperature sensing element is not wrapped with thermal insulation material and the wrong binding position, the temperature measured by the temperature sensing element is not accurate and close to the ambient temperature, which increases the opening degree of the expansion valve action, resulting in excessive liquid supply.
I. High suction temperature
1. Insufficient refrigerant charge or too small opening of expansion valve in the system results in insufficient circulation of refrigerant in the system, less refrigerant entering the evaporator, high super heat and high suction temperature.
2. The filter screen at the expansion valve port is blocked, the liquid supply in the evaporator is insufficient, the liquid quantity of refrigerant is reduced, and a part of the evaporator is occupied by superheated steam, so the suction temperature is increased.
3. If the suction temperature is too high due to other reasons, such as the poor insulation of the return pipe or the pipe is too long, the suction temperature can be too high. Under normal circumstances, the compressor cylinder head should be half cold and half hot.
J. Low exhaust temperature
The exhaust pressure is too low, although the phenomenon is manifested in the high-pressure end, but the reason is mostly produced in the low-pressure end. The reasons are:
1. The expansion valve is blocked by ice or dirt, and the filter is blocked, which will inevitably reduce the suction and discharge pressure; Insufficient refrigerant charge;
2. The expansion valve hole is blocked, the liquid supply is reduced or even stopped, at this time, the suction and exhaust pressure are reduced.