Nitrogen flow when brazing - Page 3
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  1. #27
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    Sep 2008
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    Mesquite Tx.
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    367
    It's fairly easy to do, on a larger system you can just leave one end of the tubing open while purging. On a residential condense change out, remove the schader cores, connect a hose to the regulater an set it so very little nitrogen is coming out (you don't want to pressurize the lines too much or it will be hard to braze) connect it to one of your lines and wait a few minuites for the system to purge, make sure you have flow exiting the open scrader, and begin to braze. Leave flow while the lines cool. When done use nitrogen and trace gas to leak check. Replace scrader valve cores. Leak check ok, purge nitogen out, vacuum to desired level and open valves on unit. At least you have not introduced any contaminants to system. Added time on this job 10, mins.

  2. #28
    Join Date
    Mar 2003
    Posts
    1,234
    I find it too bad that so many of the new techs are not properly instructed as to how to perform such simple tasks as nitro purging, evacuating and using a micron gauge, let alone how to charge correctly or size/check duct work. Quite often it is because they are being taught by "old timers" that still do things the OLD way and so it just perpetuates down hill from there. We offer classes on a regular basis but the ones that should be attending usually don't. Of course they also use the instruction manuals for knee pads. Glad I will be retiring in a few more years.

  3. #29
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    Jul 2006
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    NW burbs of Detroit
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    6,058
    I use dry processed CO2. The aluminium tank is lighter.

  4. #30
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    Mar 2008
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    Northeast
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    128
    CO2 is not Inert and will not stop oxidation.

  5. #31
    Join Date
    Dec 2003
    Posts
    107
    Quote Originally Posted by Vortech View Post
    CO2 is not Inert and will not stop oxidation.
    I agree. There's a lot of oxygen (O2) in CO2.

  6. #32
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    Jul 2006
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    NW burbs of Detroit
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    6,058
    Gee maybe I better stop using it then......

  7. #33
    Join Date
    Sep 2008
    Location
    Mesquite Tx.
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    367
    I see a lot of people using CO2 instead of nitrogen, I have wondered if CO2 absorbs moisture as well as nitrogen. Most jobs spec nitrogen. I agree you get a lot more CO2 in a tank, but if it is not as good as nitrogen with moisture, then I would stick with nitrogen. Although for drains, doesn't matter.

  8. #34
    Join Date
    Feb 2007
    Location
    Dallas, Tx.
    Posts
    572
    Quote Originally Posted by adamk View Post
    > Then it means that in 16 years he never read the installation instructions...

    So true...

    I guess the HVAC companies don't practice continuing education. This is the next thing to ask for when getting quotes for new systems...

    Adam
    it all depends on the company
    mike

  9. #35
    Join Date
    Dec 2011
    Location
    Twin Cities Minnesota
    Posts
    213
    The "cleaning" property's of R410A are so much better than say R22,. Been told by Reps. if you cut lines open down the road,there crystal clean! You know where it went?

  10. #36
    Join Date
    Jun 2013
    Location
    Central Florida
    Posts
    451
    A flow meter inline after the nitrogen regulator makes the right flow easier to obtain/maintain.

    Set regulator no higher than 10psi and flow meter to about 2-5LPM after purging. You'll get more mileage out of a tank.
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  11. #37
    Join Date
    Mar 2007
    Location
    tx
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    1,088
    I still have a hard time understanding the reluctance to use nitrogen while brazing. It is no joke that there is a multitude of HVAC techs who have never been taught about this. And the fact that they have been doing it for so long and still have not heard of it tells you they have never read a set of installation instructions which is something that should also be done. Even on equipment that you are familiar with the manufacturer may make some changes that you should be aware of. Even a person who does not read real well can set and read the full instructions in the time it takes to take a break and drink a cup of coffee. Some say, it takes too much time. Well are you not going to have the bottle out anyway to do your leak test? Or are you not going to do that either? The effects of not purging are more rapid and severe with todays 410 systems, but the reasons to purge are the same and have been distributed in manufacturer's literature all along. It is not something new at all. I guess there will always be those who want to short cut everything as much as possible, and if they don't have a supervisor or someone else like this educated home owner standing right there demanding they actually do their job, then they will cut all the corners they can to get out of a little work. But why not do it right and not only eliminate the chance of a lot of future problems, but also give yourself the proud feeling that comes with having done a job right and to the best of your ability?!!
    Bad information is worse than no information at all.

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  12. #38
    Join Date
    Mar 2007
    Location
    tx
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    And, while we are on the subject, maybe some of you extra smart guys can give me an answer I have searched for a long time now. We all know that O2 left in the system will react with heat and refrigerant to form hydrofluoric and hydrochloric acids, and more water. If a person does not purge during the brazing process, then oxidation is formed on the inside of the pipes and trapped in the system because it can't be removed with a vacuum. The key word here being oxygen. Here is the question. If oxidation is a chemical reaction that causes these solid particles to form inside the pipe while brazing, then is the key bad ingredient (oxygen) still present inside the system? Is there now oxygen in the system in a solid form as a part of the oxidation that can still break down chemically and cause acids to form? If the oxidation still has oxygen in it, would it not still react with the refrigerant and start causing acids in the system from the time of start up? Or, has it been chemically altered to the point where it no longer has the same effect as oxygen itself in the system?
    Bad information is worse than no information at all.

    There are three kinds of people in this world. Those who can count and those who can't!

  13. #39
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,621
    For oxygen to become a solid at "room" temp, it would have to be at a pressure greater then 1,300,000PSIG.

    Once a system is vacuumed, there would be no oxygen left in the system. Could still be moisture if the vacuum wasn't drawn low enough.
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