Question 86Refrigeration & AC - Assistant Engineer

70% to pass

After the refrigerant has been recovered, leaks repaired if necessary, the system ideally should undergo a dehydration evacuation prior to recharging with refrigerant. As shown in the illustration, besides the vacuum pump suction manifold isolation valve being opened, what would be the proper valve positions to accomplish and prove the evacuation? Illustration GS-RA-51

Diagram for USCG Refrigeration Assistant: After the refrigerant has been recovered, leaks repaired if necessary, the...
AValves 1, 2, and 3 should be back seated and both gauge manifold hand valves should be open.
BValves 1, 2, and 3 should be front seated and both gauge manifold hand valves should be closed.
CValves 1, 2, and 3 should be in the mid-position and the low-side gauge manifold hand valve should be open, and the high-side gauge manifold hand valve should be closed.
DValves 1, 2, and 3 should be in the mid-position and the low-side gauge manifold hand valve should be closed, and the high-side gauge manifold hand valve should be open.
AI Explanation

The correct answer is D. To accomplish and prove the evacuation, the proper valve positions would be: Valves 1, 2, and 3 should be in the mid-position, the low-side gauge manifold hand valve should be closed, and the high-side gauge manifold hand valve should be open. This allows the vacuum pump to draw a vacuum through the high-side of the system, effectively evacuating and removing any air or moisture. The closed low-side valve prevents air from re-entering the system during the evacuation process. The other options are incorrect because they do not properly isolate the low-side of the system or allow the vacuum pump to effectively evacuate the entire system.

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Official Resources
46 CFR Machinery & Electrical 46 CFR Engineering USCG National Maritime Center
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