Question 52 QMED03 - Oiler

The Correct Answer is D **Why option D ("Bring the part of the system to be opened to 0 psig.") is correct:** When opening any part of a refrigeration system for repairs, the primary safety goal is to prevent the release of refrigerant into the atmosphere and to avoid injury from pressurized components. Bringing the pressure of the section to be opened down to 0 psig (gauge pressure, which is equal to atmospheric pressure) ensures that there is no positive pressure to force refrigerant out when the seals or connections are broken. While it is technically difficult to reach a perfect 0 psig vacuum, the standard procedure is to pump down or recover the refrigerant until the gauge reads 0 psig or slightly below (a slight vacuum) to confirm the pressure is safe before beginning work. **Why the other options are incorrect:** * **A) Set the high-pressure cut-out on manual to prevent automatic starting.** While preventing automatic starting is crucial, this step addresses compressor operation (electrical safety) and system integrity, not the immediate safety requirement of depressurizing the specific component that is about to be opened. The preferred method for electrical isolation is to open the main disconnect switch and lock it out (LOTO). * **B) Bring the part of the system to be opened to a pressure corresponding to the ambient temperature.** Refrigerant pressures are highly dependent on temperature. Even at ambient temperature, common refrigerants (like R-22 or R-134a) will have significant positive pressure (e.g., R-134a is around 45 psig at 70°F). Opening a system under positive pressure is unsafe and illegal due to refrigerant release, making this procedure incorrect. * **C) Use the hot gas defrost line to remove any frost on the evaporator coils.** Removing frost may be a preparatory step for certain maintenance tasks to ensure accessibility, but it is entirely irrelevant to the fundamental safety requirement of depressurizing the system component before physically opening it.