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  1. #66
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    Jul 2012
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    North west Arkansas
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    I have limited space available in my service van, and with tools, parts, and cylinders of refrigerant as well as reclaim cylinders there's not a lot of room,, I work on everything at these Subways,, so I carry tanks of CO2 already for beverage systems, and it's what I use to purge and pressure test,,, it's never caused me any issues, and I use a filter drier,,
    Haven't used it in anything larger than a 5 ton ac, so can't tell you about effects when used in very large systems,, for what I do, it's been fine..

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  3. #67
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    Feb 2015
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    Waterdown, Ontario, Canada
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    Quote Originally Posted by jpsmith1cm View Post
    I have used both and I cannot tell a difference between the results.

    Some try the argument that CO2, in the presence of water, forms carbolic acid. This is true. Since we're evacuating the system to remove moisture, I don't see this as a major issue.

    Depending on the CO2 grade that you buy, it may or may not have a significant quantity of moisture in it.

    I like CO2 because there is a LOT more of it per can. I DON'T like it because that thing is HEAVY dragging it up to and across the roof.
    Hate to be a stickler for details, but CO2 plus moisture does not form carbolic acid. It forms carbonic acid, which is a weak acid.
    Nitrous

  4. #68
    Join Date
    Feb 2010
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    In a boiler room
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    Just when you think it's dead, it comes back to life!

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  6. #69
    Join Date
    Sep 2008
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    Western PA
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    Quote Originally Posted by Nitrous View Post
    Hate to be a stickler for details, but CO2 plus moisture does not form carbolic acid. It forms carbonic acid, which is a weak acid.
    Nitrous

    Appreciate the correction, Sir.

  7. #70
    Join Date
    Jul 2012
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    According to the tree huggers co2 makes "global warming". Using that would be defamory to using 410A environmentally friendly gas lmao

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  9. #71
    Join Date
    Feb 2008
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    Waffleville
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    Quote Originally Posted by Capz View Post
    Show me documentation where it states it is okay to use co2 as a brazing purge gas.

    Do a search "co2 corrosion carbon steel".

    CO2 is not an inert gas.

    Maybe my terminology was a little strong. Unless somethings have changed, I read in one of my books never to introduce co2 into refrig systems. Having pulled high vacuums on the shells of many large cryogenic vessels, I can verify that it is much easier & faster to remove nitrogen with a vacuum pump than it is co2, air or any gas with a moisture content. Boiling off moisture is what delays busting below 500mi. I needed to get below 100mi on perlite tanks, and 10mi on super insulated mylar tanks.

    CO2 will also react to high heat such as it does in the GMAW.
    Read about it here.
    http://en.wikipedia.org/wiki/Gas_metal_arc_welding
    Guess CO2 rack systems are just all wrong...

  10. #72
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    Feb 2008
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    Quote Originally Posted by Phase Loss View Post
    Yeah, I've seen that too...even on 40 year old stores.

    that can't still possibly be soot from not flowing.

    It's more likely burnt oil from high discharge temps.

    And no, I'm not joking. I've never flowed nitro during a service situation. you're talking about a handful of braze joints at best.

    IE: replacing a TXV, 3 joints, don't even wrap the valve with a rag...never had one fail....ever. Use a rose bud tip too, on full blast...for everything.
    Amen! Someone finally tells it like it is!

    No textbook fairies on this site in 2013!

  11. #73
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    Jul 2015
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    Quote Originally Posted by jpsmith1cm View Post
    Appreciate the correction, Sir.
    Uniweld does not recommend that CO2 be used for purging or pressure testing an A/C&R system because it may form carbonic acid within the system, causing premature equipment failure. However, there are certain applications where CO2 has its advantages. Because CO2 starts out as a liquid, it has a tremendous expansion rate; it is an ideal source of portable gas Pressure.

    CO2 is ideal for clearing a condensate drain line, cleaning coils, inflating tires, unclogging a sink, operating impact tools and much more.


    Norm in Arkansas

  12. #74
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    Sep 2008
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    Quote Originally Posted by greenbomb View Post
    Uniweld does not recommend that CO2 be used for purging or pressure testing an A/C&R system because it may form carbonic acid within the system, causing premature equipment failure. However, there are certain applications where CO2 has its advantages. Because CO2 starts out as a liquid, it has a tremendous expansion rate; it is an ideal source of portable gas Pressure.

    CO2 is ideal for clearing a condensate drain line, cleaning coils, inflating tires, unclogging a sink, operating impact tools and much more.


    Norm in Arkansas

    Got documentation to support that?

    I've seen documentation which does support using CO2 as a purge gas in an AC&R system.

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  14. #75
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    Jul 2015
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    Quote Originally Posted by jpsmith1cm View Post
    Got documentation to support that?

    I've seen documentation which does support using CO2 as a purge gas in an AC&R system.

    It was a copy and paste from article in another website which I no longer have . Found it looking to support CO2 brazing , which to this day I never have . Too bad for me as I have several tanks of the stuff . Lots of stuff on You Tube on Nitrogen Nothing on CO2 that I have found

    But I will go with the flow and us nitrogen to braze and purge the CHAV lines as in my mind there is too much $$$ to be wasted if I am wrong and besides I believe nitrogen is cheaper .. Also I have seen demos of brazing done with nitrogen , nice and clean welds on the inside where we want it clean as a whistle and NEVER seen any done with CO2 . I think for my piece of mind I will just continue using the CO2 in my pellet guns where I can get more bang and number of shots for the buck
    Norm in Arkansas

  15. #76
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    Quote Originally Posted by greenbomb View Post
    It was a copy and paste from article in another website which I no longer have . Found it looking to support CO2 brazing , which to this day I never have . Too bad for me as I have several tanks of the stuff . Lots of stuff on You Tube on Nitrogen Nothing on CO2 that I have found

    But I will go with the flow and us nitrogen to braze and purge the CHAV lines as in my mind there is too much $$$ to be wasted if I am wrong and besides I believe nitrogen is cheaper .. Also I have seen demos of brazing done with nitrogen , nice and clean welds on the inside where we want it clean as a whistle and NEVER seen any done with CO2 . I think for my piece of mind I will just continue using the CO2 in my pellet guns where I can get more bang and number of shots for the buck
    Norm in Arkansas

    So, you come here making a claim which you cannot back up, then backpedal when asked to support it?

    Yeah, pretty typical.

    What the heck? TRY IT! You've got CO2, you've got some copper and a torch.... Try it and see that it works. I promise that it works just as well as nitrogen does. See, I have done it and cut the joints and I defy you to tell the difference between a CO2 purged joint and a nitrogen purged joint.

    As far as supporting documentation, I have posted it in various discussions on this subject in various threads on this site and will post some again at the end of this post.

    I'm not telling you that it is wrong to use nitrogen, but that it is acceptable to use CO2 to do it. If you want to stay with nitrogen, that's FINE by me. Heck, you're at least using a purge gas and that's better than so many people do.


    CO2 meets the requirements for a purge gas in that it is inert under the conditions we have. In fact, CO2 is one of the most difficult molecules to separate in the world. The issue of carbonic acid is a non-starter for reasons which I've already explained.

    #1. If you have liquid water in the system, which is a requirement to form carbonic acid, the acid is the LEAST of your concerns.

    #2. Evacuation. Again, IF you have that liquid water in the system, you are going to be evacuating or otherwise dehydrating the system. This removes the liquid water and will completely eliminate the acid threat. Carbonic acid is CO2 dissolved in water. Evaporate the water and the acid goes away and the CO2 will be removed with the evacuation just as any other non-condensible gas is.



    As far as support for my position:

    http://www.bristolcompressors.com/fi...881/200022.pdf Page 4

    http://sporlanonline.com/literature/90/SD-068.pdf Page 2

    http://www.hvacrinfo.com/Cope_manuals/AE105_R2.pdf PG 26-3

    So, with a compressor manufacturer and one of the largest valve manufacturers around supporting my position,I feel quite comfortable in continuing to use CO2 as a brazing purge gas and continuing to recommend its use as such.
    Last edited by jpsmith1cm; 07-09-2015 at 08:53 PM. Reason: Added third reference source for CO2 as purge gas.

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  17. #77
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    Jul 2015
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    No back pedaling Here JP . The reason that I was researching this is that I use CO2 for tig welding and I thought I could use it for HVAC too UNTILL NOW I could find None that would support it. and for the life of me I could not see one reason it would not work. Yes I should have just tried it but there may have been other reasons lurking in the shadows on why not to use it.
    NOW YOU say you have done it and cut the welds , Checked the Results . PROMISE it WORKS . YOUR WORD is good enough for Me Buddy . NOW I have FOUND my Answer to the question ..
    THANK you very much for your reply . I am a newbe doing my own install because I put in 3 calls and no one showed up, too busy or I am too far in the sticks to make a profit . Also when asked about nitrogen purg brazing around here I get the old "DEER in the HEADLIGHT stare . We don't do it that way around here." Can you please help me out on one more question before you go concerning silver soldering . I know OXY ACE works but what about MAPP gas and plain straight acetylene torches for silver soldering . Your input is greatly appreciated . I will be using R410 in the new system. Changing all the 1986 out and in with 2015 2stage 18 sheer variable fan . Will be getting an expert to check my work and charging the system . I am an old guy , 66 , cheap , low income , can not afford mistakes , mine or others
    Thanks in advance and SO glad to have met you

    Norm In Arkansas
    Last edited by greenbomb; 07-09-2015 at 10:18 PM. Reason: spelling

  18. #78
    Join Date
    May 2014
    Location
    Bay Area California
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    As I understand the current debate regarding the use of CO2 as a purge gas has to do with the amount of moisture in the CO2. So what we are really doing is comparing DRY nitrogen to the CO2 available from our local wholesaler. Which is rather wet. Since the bottles are refilled by the local company that serves the beverage industry, not by the chemical gas company selling dry CO2.

    I asked our local guy at URI about getting and/or stocking dry CO2 and he said he never heard of it. But then, he probably never looked into it either.

    In previous decades, this moisture was not a problem and could easily be dealt with using our vacuum pumps and driers. But now with the common use of POE oils, the real question is how much of the moisture in the CO2 will react with the POE oil?

    My guess is not enough to make any difference. Especially if the amount of exposure time is kept to a minimum. Case in point, get a metal pan and put a cup of POE in it then leave out in the open air. How long before any color change? A crude experiment I know, but it does give you some empirical data.

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