Question 161Refrigeration & AC - Assistant Engineer

The correct answer is B) a liquid line restriction. Frosting or sweating of a liquid line is usually indicative of a restriction in the liquid line, which causes a pressure drop and reduces the temperature of the refrigerant. This results in the refrigerant temperature dropping below the dew point, causing condensation or frosting on the liquid line. The other options are incorrect because: A) high relative humidity would not directly cause frosting or sweating on the liquid line, C) refrigerant contaminated with moisture would cause issues throughout the system, not just on the liquid line, and D) proper cooling would not result in frosting or sweating on the liquid line.