argon pressure guage

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I would like some advice on gauges.  My situation is a little different and I don't want to buy more than I need.  I am installing a new ac system and I need to braze a few refrigerant lines and would like to flush them with argon= flow meter with standard regulator.  I also would like to perform a leak test with the argon but need 150psi reading. I want to use argon instead of the standard nitrogen so that I can use the argon tank with my small welder when I am done with the ac project.  I may never need nitrogen again so I don't want to buy a tank, or even rent.  Is there an inexpensive inert gas pressure regulator that you can recommend?  Or can I replace just the dial on the flow meter?If I can't do it right I will just pay someone to do the leak test but I like to learn and do things myself if possible.  Thank, Scott
Reply:Originally Posted by Hefty4690I would like some advice on gauges.  My situation is a little different and I don't want to buy more than I need.  I am installing a new ac system and I need to braze a few refrigerant lines and would like to flush them with argon= flow meter with standard regulator.  I also would like to perform a leak test with the argon but need 150psi reading. I want to use argon instead of the standard nitrogen so that I can use the argon tank with my small welder when I am done with the ac project.  I may never need nitrogen again so I don't want to buy a tank, or even rent.  Is there an inexpensive inert gas pressure regulator that you can recommend?  Or can I replace just the dial on the flow meter?If I can't do it right I will just pay someone to do the leak test but I like to learn and do things myself if possible.  Thank, Scott
Reply:Thanks OldIron, This is for my house.  I will be having a certified hvac tech check and charge the system prior to start-up in order to validate the equipment warranty so I will have them pressure check in conjunction with evacuating with nitrogen.  Want to save as much money as possible on the install and from what I've read there are a lot of ac contractors that don't braze with inert purging as recommended by the manufacturer, so I think even though I have never brazed with oxy/acetylene (have soldered enough copper tubing) I can accomplish this with good results.
Reply:nitrogen is the recomended gas I used it all the time to boost presure and leak check on transport refer units using a standard a/c guage which is capable of handling the presure, not sure about argon, a little more research might get you closer to a good answer.ron
Reply:Thanks Ron.  You may be right about the pressure characteristics of Argon vs. Nitrogen.  The condenser unit install instructions say Nitrogen or another inert gas should be used to flush during brazing but it says Nitrogen in regards to pressure testing.  Not sure if that is an exclusive statement about nitrogen or just what is common practice.  There really is no reason to choose Argon over Nitrogen for this purpose other than for me who doesn't want to buy equipment that will have no other use to me.  I assume I can use the same hose that I will be attaching to my MIG and install a schrader valve fitting to the hose.  Don't want to veer too far into ac land here though.I'll also need to check out the other gas info on this site to determine if I should just exhaust the tank for my brazing and then get a argon / co2 mix for welding.  I don't weld much but I would like to become more proficient.  I am an electrician and feel that the more I can do the better.  Never hurts to learn another skill.
Reply:Ask your local welding supply if they'll swap a nitrogen tank for an argon if you buy it from them.They have a lot of discretion, and both nitrogen and argon use CGA-580 valves. I've swapped a helium for an argon cylinder with no problem.I know exactly what I would do, which is use argon to avoid cylinder fuss, and I'd buy a cheap quality high pressure inert gas regulator off Ebay for the purpose.  About fifty bucks should do it.(I use a fixed pressure gageless Western regulator with an air chuck off my CO2 cylinder for airing trailer tires, running an impact, etc.) CGA-580 to CGA 320 (CO2) adapters are common,  and having a high pressure regulator can come in handy for all sorts of things including leak testing OA gear.
Reply:HIWhat you are talking about, brazing copper tubing you will use nickel silver solder it is for higher pressure.  This stuff works just like normal soldering that you have done but it needs a hotter temp so you use oxy/acetylene.  If all is cleaned just like soldering it acts the same.  You can get it from local welding suppliers by the pound. Then just use compressed air like stated before.  When the system is finished with the pressure check. The system will be sucked dry by the AC guy will pull the moisture out and then they fill it with Freon.  But that part needs to be done by a trained service guy.Have funTomSilver SolderFor silver solder you will need a hotter flame, so use a oxy torch or Mapp gas and a blow torch. Mapp gas is available at your local plumber supplies and hardware store. Make sure the pipe and fitting are fairly clean and heat up until both the fitting and the pipe glow red. Apply the solder and it will melt and run into the joint to form a strong join.Silver Solder Tips•All joints should be fairly clean•You must use Mapp Gas or Oxy to get the copper hot enough•You do not need flux when soldering copper to copper joints•You must use silver solder flux when soldering copper to brass fittings•Try to buy the non-toxic flux and make sure you flush the pipes when finished
Reply:I checked with one local supplier and they only have 40cu ft nitrogen.  He said they would do me a favor and swap it out with an argon/co2 after the ac project but it was $195.  I can get a 20cu ft for $70 at Harbor freight with coupon.  I'll look into the Ebay gauges though.  I guess I also need to check with the hvac tech to get an idea of what they will charge for a leak test so I have a good comparison.
Reply:Thanks Tom,  The equipment manual say not to use compressed air for the leak test.  Any idea why that is?  As long as I stay under the 150psi specified I wonder why it's not recommended?  We have a O/A torch at work that I can use.  I will do some practice first to get the heat just right.  I am used to just heating pole mounting bolts up red hot and blasting with oxy to cut through so I know I am dealing with a little more finesse here.
Reply:Originally Posted by Hefty4690Thanks Tom,  The equipment manual say not to use compressed air for the leak test.  Any idea why that is?  As long as I stay under the 150psi specified I wonder why it's not recommended?  We have a O/A torch at work that I can use.  I will do some practice first to get the heat just right.  I am used to just heating pole mounting bolts up red hot and blasting with oxy to cut through so I know I am dealing with a little more finesse here.
Reply:With all the temperature variables possible, seasonal issues, relative humidity, yadda yadda, even under the best of scenarios pumping outside air in may or may not introduce a bunch of moisture into the system. Get drops in low spots and evacuating the system gets problematic. Then there is the big problem of the air source itself. Some crusty old compressor pumping as much smoke and oil as it does air, ancient hose full of rusty water, flakes and all kinds of crud, teeny a$$ orifices in the system and all.............. All in all it makes sense for the manufacture to just make the blanket statement "no compressed air"."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:Originally Posted by Hefty4690I checked with one local supplier and they only have 40cu ft nitrogen.  He said they would do me a favor and swap it out with an argon/co2 after the ac project but it was $195.  I can get a 20cu ft for $70 at Harbor freight with coupon.  I'll look into the Ebay gauges though.  I guess I also need to check with the hvac tech to get an idea of what they will charge for a leak test so I have a good comparison.
Reply:I'd suggest running the lines yourself, but let the AC man make the connections.  That way it's his *** if it leaks.My name's not Jim....
Reply:I see your point on letting the ac guy do the brazing but then I won't have as good of an excuse to get an argon setup for my welder.  Plus then I won't have learned anything.  My welder specifies 30 cu ft/hr I think.  Is there more to the equation than volume / rate * 60= 40min of weld time.  I think that should be enough for the things I am trying to do although I could see it being a pain when I have 10min left in a bottle at the end of a project and don't want to get it filled right away.  Who knows how much I will need for the next project, probably 15min.  I really don't weld that much though right now.
Reply:Originally Posted by Hefty4690I see your point on letting the ac guy do the brazing but then I won't have as good of an excuse to get an argon setup for my welder.  Plus then I won't have learned anything. ... I really don't weld that much though right now.
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Reply:Is there any reason that I cannot use a new 200psi oxygen regulator with an adapter on my argon tank for pressure testing my lineset?  Harbor freight has one for 30 or 40 bucks.  I only anticipate needing it once.