The only fluids circulating within a refrigeration system should be refrigerant and oil. Any other fluids contained within the system may reduce its capacity and possibly cause harm to the system. One common contaminant that can enter a system is atmospheric air. Air contains nitrogen, oxygen, and moisture, all of which are harmful to a refrigeration system.
When air is contained in a system it will become trapped in the condenser and will not condense. It will take up space, causing less surface area for the refrigerant to condense.