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

Illustration GS-RA-51: the U.S. Coast Guard has not released this illustration.

Question

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

Illustration GS-RA-51: the U.S. Coast Guard has not released this illustration.

Accepted Answer

Option D: Valves 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.. Proper deep evacuation requires isolating the vacuum pump while monitoring for pressure rise. Setting system service valves 1, 2, and 3 to the mid-position and opening the high-side manifold valve exposes the entire system simultaneously to the deep vacuum source.