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  1. #1
    I will be having a new Trane 2.5 or 3 ton XR12 split ac system installed soon. I feel pretty good about the contractor that will be performing the install, but would like some general recommendations from you guys. I want to know if it is imperative that the installer flow nitrogen when soldering or brazing the lines, or is this just an extra measure that is not really necessary. Also, which is the better or preferred method , soldering or brazing? Approx. how long should a new system be evacuated after the install? Should I request that an inline filter/dryer be installed at the time of installation?

    Thanks

  2. #2
    Join Date
    Apr 2004
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    420
    Doubt he needs you to tell him if they're reputable.

  3. #3
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,369
    If your installers know their stuff, they will:

    a) Flow nitrogen during brazing (not soldering)

    b) Pull a 500 micron vacuum with little rise after blank-off

    c) Install a liquid line drier

    You should not have to request these items be performed if the contractor is reputable and takes pride in their work. I don't see any harm in asking if these procedures are standard practice prior to accepting the bid. If you find a contractor that includes it in writing in the bid, so much the better.

    I recently had to select a foundation repair contractor for my house. I chose the one that not only I had a positive prior experience with on another house, but their procedures were clearly outlined on the contract, as part of the contract. The other bidders did not include such detail, and although one was more competitive, I chose the higher bid with the greater detail and good history. The work began yesterday and they so far have done everything called for to do the job right.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Join Date
    Jan 2004
    Posts
    933
    Shophound-LLdrier on every new install?
    respectfully, what is your reasoning?
    Still learning opinions welcome.

  5. #5
    Join Date
    May 2004
    Posts
    12,227
    If nothing else an ounce of prevention is worth a pound of cure.

    Every system I have put in from residential to commercial gets a liquid drier. I will spend a few dollars everyday if it prevents a recall with a blocked metering device.



  6. #6
    Shophound, I agree with all you stated including the drier (whats $10.00).

    If it were me, brazing, (with nitrogen) not solder.

    Vacuum, 500 microns, and with a good blank off, 1 or 2 hours. I would recommend overnight and a double or triple evacuation process. (Yes Im extreme)

    A simple addition to your system is a TXV valve. I think upgrade costs are relatively low, and the stable and improved performance will pay you back in the future.

    An informed customer sure keeps a tech on his toes, and pulling his hair out. I think it is a good thing to be informed, and hold people accountable. But to many times, the home owner goes for the lowest bidder, instead of finding a responsible company.

    When its done, post some pictures.

    Oh, I almost forgot. Offer the guy a glass of water, sandwich, be nice while you looking over his shoulder

    [Edited by kerndt on 04-13-2005 at 02:58 PM]

  7. #7
    Join Date
    Jan 2004
    Posts
    933
    Sorry, brain fart, I read L-L drier but thought suction drier agreed, i like it when the manufacture takes care of it with a good sized drier included
    Still learning opinions welcome.

  8. #8
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,369
    Originally posted by 2story
    Sorry, brain fart, I read L-L drier but thought suction drier agreed, i like it when the manufacture takes care of it with a good sized drier included
    2story, no problem. I would also agree that if OEM put in a beefy enough LL drier, adding one on the lineset would seem redundant.

    I'd only use a suction line drier for cleanup after a burnout, and then I'd want to watch the pressure drop across the core after a little running time. Ideally it should be pulled after its done its duty...hard to do in the real world, unless you're always on site like I am.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  9. #9
    Join Date
    Jan 2004
    Posts
    933
    shophound, i have a thread in the job discussion area entitled "which way do I go" i would appreciate your advise, if you would not mind.
    Sorry to derail this thread.
    Still learning opinions welcome.

  10. #10
    Join Date
    Apr 2004
    Location
    Niantic, Illinois
    Posts
    545
    Originally posted by drcustom
    Doubt he needs you to tell him if they're reputable.
    Trane equipment comes with liquid line filter dryers already insatlled inside the condenser cabinet near the service valves. Adding a second one will drive up the head pressures and strain the compressor. Espeacialy on 410 a. A company I used to work for had an installer adding the redundant drier on 410 systems, the following summer I returned to rplace compressors in about 2/3 of them. It was that fast. Luckily the guy didn't last long with this company. In fact the last time I saw him he was driving a dump truck for a gravel company.

  11. #11
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,369

    2story

    See my reply to your post in Job Discussions.

    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  12. #12
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,914
    by Dick Shaw
    ACCA Technical Education Consultant

    As is usually the case, the boss is right! Serious consequences can result down the road with systems that brazing took place without sweeping (purging) nitrogen through the copper tubing during installation or service brazing procedures.

    Lets take a look at the brazing process and why the nitrogen sweep is important. Copper, brass and bronze are non-ferrous metals that can be joined with these as well as other dis-similar metals such as copper coated steel. The pipe/tubing, equipment and fittings when joined in a brazing process of over 800 F. can make for a safe, clean and leak free system used in high pressure refrigeration and air conditioning.

    The melting point of copper is 1,981 F. and the brazing process requires temperatures above 800 F. The actual melting point of the solder depends on the alloys it contains and the percentage of silver contained. At these high temperatures, installations, such as refrigeration/air conditioning, medical gas, high-purity piped systems that must result in a clean interior, the use of an inert gas such as nitrogen purged during the brazing process is required. The purge gas displaces oxygen from the interior of the system while it is being subjected to the high temperatures of brazing and therefore eliminates the possibility of copper oxide formation on the interior tube surface .

    A good example is the black scale (copper oxide) that we see accumulated on the outside of a pipe when it is brazed. The inside of the pipe looks the same as the outside where the black scale accumulates. The oxygen (on the inside and outside of the pipe) causes this black scale. And, by displacing the oxygen with dry nitrogen we prevent black scale formation and end up with a clean system interior.

    When a refrigeration or air conditioning system is manufactured and field installed it results in numerous connections, the scale can amount to a considerable quantity if dry nitrogen sweep/purge is not incorporated. When a refrigeration/air conditioning system is started the scale begins to move with the refrigerant and oil. The scale is either trapped in the oil, the filter drier(s), or the metering device, whichever it reaches first. Just like noncondensables and other contaminants, we dont want scale in a refrigeration/air conditioning system to be the cause of system failure. So, lets keep listening to the boss.

    No Heat No Cool You need Action Fast

  13. #13
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Yep that black scale is the one and only reason to use nitro when brazing. Just one little itty bitty piece can screw up a metering device and cause you big time headaches. Sadly enough there are many techs who were never taught this even in todays classes. Its a pain in the buttox to carry them heavy nitro cylinders to the unit but in the end it saves mucho headaches.

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