You seem to have figured out the basic idea pretty well, but you really should keep the time the unit runs while pumping down to an absolute minimum because the stress on the compressor is huge when the suction pressure drops below the normal range and the compressor isn't getting lubrication or cooling without refrigerant flowing since the refrigerant carries the oil and cools the compressor. Also, you really don't want to run the system into a vacuum during pump down. Not only does that put a huge stress on the compressor, but when you disconnect the lines, you suck air (which contain moisture) into the system. Yes, you can suck the air out of the system with a vacuum pump, but the oil left in the lines and indoor coil will absorb the moisture, which can't be removed with a vacuum. Once you disconnect the lines, you need to immediately seal the ends to keep moisture out because the moisture will break down the oil and turn it into acid.
You seem to have figured out the basic idea pretty well, but you really should keep the time the unit runs while pumping down to an absolute minimum because the stress on the compressor is huge when the suction pressure drops below the normal range and the compressor isn't getting lubrication or cooling without refrigerant flowing since the refrigerant carries the oil and cools the compressor.
Also, you really don't want to run the system into a vacuum during pump down. Not only does that put a huge stress on the compressor, but when you disconnect the lines, you suck air (which contain moisture) into the system. Yes, you can suck the air out of the system with a vacuum pump, but the oil left in the lines and indoor coil will absorb the moisture, which can't be removed with a vacuum. Once you disconnect the lines, you need to immediately seal the ends to keep moisture out because the moisture will break down the oil and turn it into acid.
did you re-commission this unit?
How much pressure does yours run?