I am working on a York YT R123 Machine. I new it had a leak, so I pulled all the refrigerant. Perfomed a leak search. Found the leak in the releif. Replaced the relief. Evacuated the system, charged it back up. Now I have a portale purge unit on it. Should I leave the purge unit on all night? Or is there a formula to calculate how long to leave it on? There is 810 lbs in the system.