Required Evacuation Levels
For low-pressure equipment manufactured after November 15, 1993, the system must be evacuated to 25 mm Hg absolute before opening for service. For equipment manufactured before that date, the requirement is 25 inches Hg vacuum (a gauge measurement relative to atmospheric pressure). These evacuation levels ensure that the maximum practical amount of refrigerant has been recovered from the system.
Post-11/15/93 equipment requires evacuation to 25 mm Hg absolute; pre-11/15/93 requires 25 inches Hg vacuum.
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