Air in the refrigeration system

There are two most common ways air gets into the system:

1) At the time of charging if hoses were not blown by freon or from the recovery cylinder (previously contaminated reused freon). 2. The air is not removed by CFC vapors from the system after inspection or repair done.  

Brief identification of the air in the system:

1) The discharge pressure increases by some amount in comparison with the normal operation.
2) The arrow of the discharge manometer may vibrate.
3) The compressor cooling capacity decreases.
4) The system energy consumption increases.

Exact identification:

1 ) Collect all freon from the system into the condenser by operating compressor with the condenser discharge valve closed. 2) Close the suction and discharge valves on the compressor after it has been stopped.
3) Open the inlet and outlet valves of the seawater completely on the condenser.
4) Cool freon in the condenser with seawater until the temperature of the seawater at the inlet and outlet of the condenser becomes the same (for example, 19C = 19C).
5) According to the condenser manometer, determine the condensation pressure of freon at a specific temperature. For example, when 19C, the pressure on the manometer is 8.2 Kg/cm2. 6) With the help of the entropy diagram for your freon, determine what is the additional vapor pressure of Freon (without the presence of air in it) at the temperature = 19C. We obtain P = 5.6 Kg/cm2. Add 1 atmosphere of 5.6 + 1 = 6.6 Kg/cm2. 7) The presence of air in the system is determined by the partial air pressure in the system, i.e. when comparing the reading of the manometer of the condenser 8.2 Kg/cm2 and obtained from the diagram P = 6.6 Kg/cm2, we see that partial pressure of air = 8,2 - 6,6 = 1,6 Kg/cm2.

How to vent the air from the refrigeration system:

1) The air from the system is removed through a vent valve located at the top of the condenser or any nozzle on the top of the condenser (for example, a pressure gauge, etc.). 2) It is necessary to release 1.6 kg / cm2 of Freon to P = 6.6 kg / cm2.