What property of POE oil used with HFC refrigerants necessitates liquid-line filter driers?

• A. It is very hygroscopic
• B. It is highly flammable
• C. It has low lubricity
• D. It is non-polar and inert

Answer: (A)

POE oils used with HFC refrigerants readily absorb moisture from the air and from the system. That moisture, if left in the liquid line, can travel with the refrigerant and interact with the oil and refrigerant, especially under hot conditions, forming acids and sludge that can corrode copper parts, reduce lubrication quality, and damage components. A liquid-line filter drier is placed in the liquid line to remove water and contaminants from the refrigerant as it passes, preventing moisture from reaching the compressor, metering devices, and evaporator. This drying action is the key reason for needing a liquid-line filter drier with POE oil systems. The other properties listed don't drive this need.