The performance of air conditioning refrigerant shortage and the judgment of the amount of charge

First, the performance of the refrigerant is insufficient 1 the tracheal valve is dry, and there is no obvious cool feeling by hand touch. The reason is that the insufficient refrigerant causes the boiling end point in the evaporator to advance, the refrigerant superheat of the valve is increased, and the temperature of the valve is increased, which is greater than the dew point temperature of the outdoor air.
2 liquid pipe valve frosting. The reason is that the insufficient refrigerant causes the pressure in the liquid pipe to drop, and the boiling point is lowered, so that the valve temperature is lower than the freezing point.
3 Open the indoor unit panel and remove the filter. You can find some evaporator condensation or frost. The reason is that due to insufficient refrigerant, only some of the evaporators have boiling heat absorption, so that the cooling area is correspondingly reduced;
4The outdoor unit does not have a sense of heat. The reason is that the refrigerant is insufficient, the condensation pressure and the condensation temperature are lowered, and the exhaust air temperature is also lowered.
5 The drain hose drain is intermittent or not drained at all. The reason is that the evaporator cooling area is reduced, the dew condensation area is also reduced, and the amount of condensed water is reduced.
6 Outdoor engine gas and liquid valves are oily, and there is leakage of oil. The reason is that the refrigerant and the frozen oil have a certain mutual solubility, and the fluorine escapes from the leak point and enters the atmosphere, and the oil adheres around the leak point.
7 Measure the operating current of the air conditioner is less than the rated current. The reason is that the refrigerant is insufficient to reduce the compressor working load and the current is lowered.
8 The pressure measured from the outdoor unit filling port is less than 0.45Mpa. The reason is that insufficient refrigerant causes a drop in evaporation pressure.

Second, the accurate judgment method of refrigerant charge
1. Measure the pressure. The temperature of the saturated vapor of the refrigerant is corresponding to the pressure. If the evaporation temperature of the refrigerant is known, the corresponding evaporation pressure can be detected. The gauge pressure of this pressure is indicated by the high and low pressure gauges. Therefore, it is possible to judge whether or not the refrigerant charge amount is appropriate according to the pressure value of the pressure gauge installed on the system.
For example, the evaporating temperature of the air conditioner is 7.2 ° C, and the condensing temperature is 54.5 ° C using R22. Check the saturation temperature and saturation pressure of R22 to determine the evaporation pressure value and the condensation pressure value. The table can be seen that the corresponding absolute pressure value of R22 at 7.2 °C is 0.53Mpa (5.3kg/cm2) and the corresponding absolute pressure value at 54.5°C is 2.11Mpa (21.1kg/cm2), and this pressure is converted into the gauge pressure value. can.
The high- and low-pressure pressure gauge or the composite pressure gauge is used to test the refrigeration system in the fluorine-filled system. If the high and low pressure gauge pressure values ​​meet the above range, the refrigerant charge is appropriate; if the high and low pressures are low, it indicates The amount of charge is not enough; if the high and low pressures are high, it means that the charge is too much. The pressure measurement method is relatively simple and often works during maintenance, but the disadvantage is that it is relatively thick and the accuracy is not high.
2. Measure the weight. When filling the Freon, prepare a small scale in advance, put the refrigerant cylinder into a container, and then inject cold water below 40 °C in the container (for low-pressure charging refrigerant vapor of the air conditioner). Note the weight of the cylinder, warm water and container before filling. Pay attention to the pointer during the filling process. The filling can be stopped when the amount of refrigerant reduction in the cylinder is equal to the required amount of charge.
3. Measure the working current. The working current is measured with a clamp-type ammeter. When cooling, the ambient temperature is 35 ° C, and the measured operating current corresponds to the current on the nameplate. The higher the temperature, the higher the current, and the lower the temperature, the lower the current. In the case of normal fan and two heat dissipation numbers, the current values ​​measured by the air conditioner are compared.
4. Measure the temperature. Using a semiconductor thermometer, the temperature of each point such as the inlet and outlet of the evaporator and the outlet of the liquid collector is measured to determine how much the refrigerant charge is. The temperature difference between the inlet of the evaporator (150 mm in front of the capillary) and the two points of the outlet is about 7-8 ° C, and the temperature at the outlet of the collector should be 1-3 ° C above the outlet of the evaporator. If the temperature difference between the inlet and outlet of the evaporator is large, it indicates that the cooling capacity is insufficient. If the frosting section of the suction pipe is too long or frost is formed near the compressor, it indicates that the refrigerant is excessively charged.