[Steeveedee]

Back in the day, we used to do a "sweep" of the system, which entailed putting in refrigerant and then venting it. Do it a few times, and there will be very little air and/or moisture left. Usually done after a replacement of a part, and the system got a new receiver dryer as part of the deal. You can do the "sweep" with a refrigerant that isn't controlled like R-12, since R-290, for example, is not considered an ozone depleter. Thus, you would not have to evacuate the system.