Finally had the time to get my system ready to pull vacuum !! I was doing an initial vacuum test to verify that the system has no leaks and once that is confirmed I will be pulling a vacuum to boil off any moisture (waiting for outside temp to be in the 80s and going to rent a good pump). I pulled a vacuum maybe 28"+ or so and closed the high and low side valves on the gauges, disconnected the service line from the vacuum pump and connected it to the gauge (no shut off valve on pupmeP. I opened the low side valve and the vacuum fell to approx 10" (I am guessing due to disconnecting the service line); it has been holding at this level for now for more than 3 hours. My question if the system is showing that it is holding a vacuum.....how long should I wait to verify that there are no leaks in the system ? I have read 10-15 minutes, which is what I am guessing most shops do, however I suspect they use micron gauges that show any small leaks quickly. Any tips or suggestions would be a great help. Thanks.
Edited: Thu April 24, 2008 at 1:05 AM by y2k600f4
Pull a vacuum for at least 30 minutes, close off both handwheels and walk away. Come back after 30 minutes..if it holds, you're there. Pull more vacuum for a hour at least. Here is a point a lot of people miss. To boil off all the moisture, you need to use a micron guage. Without one, it's hit or miss so the longer the vacuum process, the better off you are. The manifold guage can read 29inches and you still can have moisture in the system. If you can find the time, an over night vacuum is better.
Dougflas....thanks for the tips. Actually I feel stupid, after thinking about it, it looks like I opened the low side on the gauge which was the cause for the vacuum drop (don't know what I was thinking). Just pulled a vacuum this morning for a few minutes and closed both hand wheels. Now the vacuum seems to be holding (without any initial drop), will let it sit for the rest of the day. Next step is to rent a quality electric pump and get the system evacuated the RIGHT way !
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