Quote:
Originally Posted by TomWS
Further, if I then vacuum the lines to 500 microns (or, at least, below the vapor pressure of water), then the bulk of even that limited amount of water will be removed from the linesets?
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If you are prepared to Vac to 500 Microns or lower, you can use water to do your leak test if you really want. The beauty of using a liquid is a leak becomes apparent _really_ fast as a drop means a massive pressure difference.
Now, in the olden days (read mostly before R410a but not always) pressure testing more than a couple of hundred PSI was a bad idea as the gas could leak past the service valves and contaminate the charge. "Mostly" these days it's not much of an issue.
I have a second fan-coil in my ceiling at the moment that is unconnected. I have a "holding charge" of 400psi of N2 in it. I figure a month or two of 400PSI when I plan to use it on R290 (so maximums of less than 300) is a pretty good strength and leak test.
Back to vacuum though.. If you vac to 500 Microns or less, and it holds there (and its not freezing out), then you _know_ you have no water and have removed enough of the non-condensibles not to worry about it. If you vac to 500 and it slowly rises to 1000 or more, then you have moisture that has turned to Ice and is slowly melting or subliming.
Look at it this way. I have a fridgy mate who installs A/C units all day long. He follows the cheap Chinese instructions and terminates the lines, then purges them with refrigerant. His attitude is "the manufacturer recommends it". Is it any wonder than modern day splits last just long enough to endure the warranty period? Do it properly (with a _good_ vacuum) and you are multiplying your chances of things lasting longer than the warranty on the packet.
I installed my own splits, and I just installed my own ducted heat pump. The money I saved on the installs more than covered the cost of an E-bay Vac pump, gauge set, N2 Reg and misc tools (many times over. I'm WAY ahead!). I _know_ it's done right. Having said that, the law does not smile on me like it does my mate who purges lines with refrigerants.
I don't know what copper costs over there, but a roll of 3/8 | 5/8 lineset cost more than my vac pump + gauge set together. A bottle of N2 costs me $60 per fill and $15 per month. I can do a _lot_ of purging and testing for that, and when I run out for purging, a wise man taught me I can use propane to purge with.
There's doing it yourself, and then there's doing it yourself the *right* way.