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  1. #14
    Join Date
    Oct 2010
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    Anderson, South Carolina, United States
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    Quote Originally Posted by hvac5646 View Post
    The h2o content is emphasized because we use gas to sweep the system between evacs and blow out impurities. The less h2o the better.
    A deep vacuum will remove the minute amount of h2o.

  2. #15
    Quote Originally Posted by jtrammel View Post
    A deep vacuum will remove the minute amount of h2o.
    You want to add time to your evacuation? If you are not concerned about the moisture content of your purge gas than you are disregarding every lesson ever taught on evacuation and system de hydration.

  3. #16
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
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    I don't want to add time, although there is usually plenty to do while pulling a vacuum. I don't have an inert gas moisture meter so I have to trust what the supplier gives me.

  4. #17
    Quote Originally Posted by jtrammel View Post
    I don't want to add time, although there is usually plenty to do while pulling a vacuum. I don't have an inert gas moisture meter so I have to trust what the supplier gives me.
    One good test I learned is to release about 75psi thru a 1/4 hose and let the gas hit a mirror. If it leaves behind a film or residue there is oil and an undesirable amount of moisture in the tank. Than you have to run your gas thru a filter drier or take the unpure tank back.

  5. #18
    Join Date
    Sep 2005
    Location
    Atlanta GA area
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    21,523
    Remember that how deep a vacuum goes and how well it holds is a measure of dryness.

    Most of the time a single pass with the vacuum pump draws the system down to around 200-225... and it rises to less than 400. Now that is a good vacuum for residential work... even 410. If it is stubborn... a triple evac will allow me to go below 200 with a rise to less than 300 if I wanted to do so.

    Now I fully realize in refrigeration work deeper vacuums are desirable, and sometimes necessary.

    In residential work... the difference is negligible.

    Experience... many years (in my case decade +) and probably over a thousand systems opened and closed... teaches one what is necessary ans what is splitting hairs.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

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  6. #19
    Join Date
    Feb 2010
    Location
    In a boiler room
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    7,184
    Quote Originally Posted by hvac5646 View Post
    One good test I learned is to release about 75psi thru a 1/4 hose and let the gas hit a mirror. If it leaves behind a film or residue there is oil and an undesirable amount of moisture in the tank. Than you have to run your gas thru a filter drier or take the unpure tank back.
    It better be a brand new hose, otherwise the residue could be from what was in the hose. Even a brand new hose could have oil residue left in it from the manufacturing process.

  7. #20
    Join Date
    Mar 2010
    Location
    Morgan Hill Ca.
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    1,219
    I think this discussion went way off track.

    The OP mentions purge, not evacuation.

    Purging with nitrogen is to "displace the oxygen during the brazing process", you have to realize that the moisture content is pretty much irrelevant in most of our uses.

    Co2 in the meantime causes condensation because it is in a liquid state when released and that change of state can cause WAY more issues than static moisture in "dry nitrogen". Nitrogen is in a gaseous state and does not cause the condensation issues.

    So what's the argument? Because dry nitrogen should not be used because it is not lab quality? Give me a break.

    Something to realize too, the molecular structure of nitrogen is a bit larger than that of o2, this incompatibility is where the moisture discussion becomes moot.

    IMHO using CO2 will cause more problems than they will eliminate.

    Unless of course CO2 is indeed the refrigerant being used... Then of course the action changes. Nitrogen also does not convert as much as carbon dioxide does when brazing temperatures are realized. If you really want to get trick, use argon.

    GT
    If a day goes by and you have learned nothing, I hope you got a lot of sleep.

  8. #21
    Join Date
    Mar 2007
    Location
    wedged in freezer shelf
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    7,048
    Trick would be CO2 purge, CO2 pressure test and CO2 leak check with a CO2 detector.

    Cut down on some steps it would ;-)

  9. #22
    Quote Originally Posted by chuckcrj View Post
    It better be a brand new hose, otherwise the residue could be from what was in the hose. Even a brand new hose could have oil residue left in it from the manufacturing process.
    Jeez... do I have to spell it out for you step by step?

    Of course the hose is clean and is re-cleaned after after each test. According to mfg specs it is cleaned with isopropyl alcohol. And the test hose is dedicated.

    We clear now Mizer Johnson, boss?

  10. #23
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
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    Quote Originally Posted by hvac5646 View Post
    Jeez... do I have to spell it out for you step by step?

    Of course the hose is clean and is re-cleaned after after each test. According to mfg specs it is cleaned with isopropyl alcohol. And the test hose is dedicated.

    We clear now Mizer Johnson, boss?
    How do you find time to do all of this stuff, I barely have time to think I'm so buisy.

  11. #24
    Quote Originally Posted by GT Jets View Post
    I think this discussion went way off track.
    .

    Co2 in the meantime causes condensation because it is in a liquid state when released and that change of state can cause WAY more issues than static moisture in "dry nitrogen". Nitrogen is in a gaseous state and does not cause the condensation issues.

    GT
    CO2 is charged as a braze purge in gas state, not a liquid. Plenty of ways to take what you say on condensation.Care to expand?

    On the CO2 molecular weight being lower than nitrogen...that is a plus because the CO2 will show smaller leaks than nitro will.


    Quote Unless of course CO2 is indeed the refrigerant being used... Then of course the action changes. Nitrogen also does not convert as much as carbon dioxide does when brazing temperatures are realized. If you really want to get trick, use argon. End quote


    Co2 is the end of the combustion process...it cant "convert" as you put it at brazing temps.

  12. #25
    Quote Originally Posted by jtrammel View Post
    How do you find time to do all of this stuff, I barely have time to think I'm so buisy.
    All what stuff? Boss has had his service procedures in place a long time. They are part of a routine any business follows.

  13. #26
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
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    7,667
    Quote Originally Posted by hvac5646 View Post
    All what stuff? Boss has had his service procedures in place a long time. They are part of a routine any business follows.
    Cleaning your hoses with alcohol and getting out a mirror to blow against, how long does it take you to do an install. I'm all for using good practices and make a point to do them but around here my customers or boss aren't gonna let me spend 3 days on a simple changeout.

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