How to determine air ingress into the refrigeration system and remove it?
There are two most common ways air gets into the system:
- At the time of charging if hoses were not blown by freon or from the recovery cylinder (previously contaminated reused freon).
- The air is not removed by CFC vapors from the system after inspection or repair done.
Brief identification of the air in the system:
- The discharge pressure increases by some amount in comparison with the normal operation.
- The arrow of the discharge manometer may vibrate.
- The compressor cooling capacity decreases.
- The system energy consumption increases.
Exact identification:
- Collect all freon from the system into the condenser by operating compressor with the condenser discharge valve closed.
- Close the suction and discharge valves on the compressor after it has been stopped.
- Open the inlet and outlet valves of the seawater completely on the condenser.
- 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).
- 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.
- 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.
- 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:
- 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.).
- It is necessary to release 1.6 kg / cm2 of Freon to P = 6.6 kg / cm2.
