Manifold pressure gauge circuit diagram

6. Refrigerant filling. When

adding refrigerant to the air conditioning system, the air and moisture inside the system must be exhausted in advance. At the same time, an appropriate amount of refrigerant must be added, not too much or too little, otherwise it will cause malfunction of the air conditioning system.

In order to measure the vacuum degree of the air conditioning system and whether the pressure after filling the refrigerant is appropriate, manifold pressure gauges, vacuum pumps and other devices can be used, as shown in Figure 28.

There is a multi-channel valve seat on the manifold pressure gauge. Low-pressure and high-pressure gauges are fixed on the valve seat. The low-pressure gauge is used to display both the pressure on the low-pressure side of the refrigeration system and the degree of vacuum. It is also called a vacuum pressure gauge. Vacuum The reading is 0~30 inches (0~760mmHg), and the pressure scale is from 0~6Opsi or above (pounds/inch2 is about 0~0.4lMPa, that is, 4.2kg/cm2, 1 pound/inch2=1psi=0.07k cmz).

The measuring range of the high-pressure gauge is from 0 to 5OOpsi (about 0 to 35.2kgf/cm2, 3.58MPa), and it is connected to the high-pressure side of the air conditioning system during operation. The two meters are mounted on the upper part of a meter base. There is a manual stop valve at each end of the meter base, and there are three access interfaces at the lower part. If the stop valve is open, the refrigerant R-12 in the air conditioning system can be discharged to the atmosphere through the passage of the meter base and the intermediate passage pipe (the refrigeration oil can be collected in an appropriate container); these two stop valves must be closed if the high and low pressure readings are to be detected. ;To fill R-l2 refrigerant, a hose must be used. Connect the fluorine (R-12) container (tank) to the intermediate interface, and then open a stop valve to allow R-12 to enter the refrigeration system from the high-pressure side through the meter seat or from the low-pressure side (Figure 29).