Double / triple sweep?

[flange]

just had a job with wet system, contamination in the oil due to shietty evacuation. The so called factory expert claimed to have done "proper" evacuation in a day after repairs. We tested by doing oil analysis and megging, and made them redo it, with my guy witnessing. took four days to get the system right. first two and a half were first pull down. System was swept to 1500, broke to 2 psi, 1500, 2 psi, and finally 500. guy thought it was a waste of time too, but when checked again after charging, megger readings went up seven fold, oil analysis clean, moisture indicated very dry. He is now a believer, he says....

[ar_hvac_man]

In small,capillary refer systems; I find that it does help when I'm having trouble getting to 500 mics. May not be as useful in residential work but has definitely helped me.

Ditto. Seems like these systems always want to hover around 725. Putting a 1/3 hp in in the morning and will be breaking vac at least twice with n2.

[mofotech]

We always break a vacuum at least once with dry nitro after 1000 micron then pull it down again to below 500. Was taught that a very fast vac can make the moisture freeze and the dry nitro was to get it into vapor form. Might have been an old wifes tale but see no need to test the theory for $1 worth of nitro and an extra minute of time.

Its true. Also can happen with oversized vacuum pump pulling deep vacuum too fast.

[Birmingham]

everyone is going to say this is not possible

I have repaired at least 5 water source systems this year that had compromised coils, water flooded refrigerant systems. one had been flooded for over 1 year. Zero exaggeration. any amount of moisture can be removed dependent on how bad you want to get it out. im tired of hearing people say that if a line set is open and it rains its ruined. pull vac, break with nitro, and change oil as needed. it will come out.