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 A: 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 evacuation requires isolating the compressor via mid-positioned service valves while opening the high-side manifold valve to allow the vacuum pump to pull a deep vacuum across the entire system.