Question 101Refrigeration & AC - 1st Asst/Chief

The correct answer is C) the system secondary refrigerant to freeze. Charging liquid HCFC-123 into a system under deep vacuum can cause the secondary refrigerant (usually water or a water-glycol mixture) to freeze. This is because the deep vacuum reduces the boiling point of the secondary refrigerant, allowing it to freeze even at relatively warm temperatures. Unless the necessary precautions, such as pressurizing the system with an inert gas before charging, are taken, the frozen secondary refrigerant can damage the system. The other options are incorrect because: A) a rupture disk is not directly affected by charging into a vacuum, B) air and moisture entry is more of a concern when charging into a system not under vacuum, and D) the purge unit operation is not directly related to the risks of charging into a deep vacuum.