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Old 10-17-09, 10:34 PM   #1
Xringer
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Default HVAC Vacuum pump question

I purchased a vacuum pump to use when installing a new mini-split.

http://ecorenovator.org/forum/projec...project-4.html


And tonight I'm looking at different vacuum gauges when I find this:

FAQ - Vacuum Gauges

"When I hook up the VG64 to a new vacuum pump and isolate the pump, I get an initial reading of 440 microns and then a quick rise to 1200 microns? Always use vacuum hoses not charging hoses as they permeate and leak. Also new hoses have gas in them, so they must be gassed out. If this procedure is not followed, the gases in the hoses will cause a rise in vacuum readings once the vacuum pump is shut off."


My hoses are clearly marked as charging hoses, but have cut-off valves.

http://ecorenovator.org/forum/projec...project-5.html

~~~

So, this is my plan.. Once the pump has done it's work, and we have
what we hope to be a good vacuum,(29.9"?) I should be able to shut off the
hose, right at the service port (isolating the line-set) and let vacuum do it's thing inside the line-set tubes.


After waiting for a while, I'll turn the pump back on and wait until it shows
29.9" again, then open the hose valve. (The hose and line-set pressure matches?).

IF, the line-set was still holding a good vacuum, the gauge needle should not drop at all.
If it does, due to out-gassing, I'll keep repeating the process until there is no drop..

That's the best plan I can come up with.. Any of you guys have any suggestions?

Thanks,
Rich

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