During installation the system should be kept as clean and dry as possible, with the least exposure to air. Avoid the entry of foreign matter such as solder fluxes, solvents, metal and dirt particles, and carbon deposits; the last are the outcome of soldering joints without passing a neutral atmosphere through the pipework.
Failure to take precautions may result in corrosion caused by air and moisture, or by an oxidizer under high temperature conditions. Other problems include:
1. Copper plating due to contaminated oil. It forms on bearings and planed surfaces in high temperature areas. Moisture in the system can also be the cause.
2. Freezing, which may take place in the system components if the correct dehydration procedure (evacuation) is not adopted.
3. Sludging, that is the chemical breakdown of oil under high temperature conditions in the presence of non-condensables.
The chemical breakdown or thermal decomposition of both refrigerant and oil in temperatures in excess of 150o C (300o F) is more likely to occur with refrigerants R22 and those in the R500 group. In the presence of hydrogencontaining molecules the thermal decomposition produces hydrochloric and hydrofluoric acids, a condition which is wholly undesirable if hermetic or semi-hermetic compressors are employed. For this reason it is imperative that the evacuation period is adequate.
