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  1. #1
    Join Date
    Apr 2004
    Location
    Des Plaines,IL
    Posts
    1,015
    I have noticed that with a few of the compressors I have had to changed on on a few Armstrong package units, and a condenser coil I had to change on a Carrier RTU, I have ran into problem of having partially plugged evaporator coils. Now whenever I braze, I always have a nitorgen purge going through the system to reduce the chance of oxidation inside the copper lines. I was talking to the tech who either changed the compressor on the Armstrong systems or repaired the evaporator coil on the Carrier RTU and he indicated that he never uses nitrogen purges when brazing. I am thinking that maybe these previous compressor changeouts and repair resulted in oxidation forming in the connection after the liquid line dryer and before the metering device. I have been only doing this for about two years now, so any thoughts from the ones with years of experience would be helpful.

  2. #2
    Join Date
    Dec 2002
    Posts
    174

    my experience...

    ...with the carriers is that you must nitrogen drift them because they will clog up resulting in compressor changeouts

  3. #3
    Join Date
    Apr 2004
    Location
    Des Plaines,IL
    Posts
    1,015

    Nitrogen Purge

    I alawys wondered does that nitrogen purge through the system reduce the oxide deposits or are they elimintaed all together?

  4. #4
    Join Date
    Jan 2004
    Posts
    1,174
    It eliminates them altogether but it is easy to get lazy and not carry yout 50# bottle 2 miles through a mall or whatever so often doesn't get used.I sometimes do it and sometimes don't, just depends on how I feel.

  5. #5
    Join Date
    Jun 2004
    Location
    Richmond Virginia
    Posts
    1,078
    I've worked on many roofs with several identical units installed at the same time. You can walk up to one that is twenty years old and has the original compressor, filter drier and rusty service valves that are impossible to remove but measure the temp drop and line temperatures and determine that the unit is functioning fine. Conversely, the next unit could be on its fifth compressor and has had numerous leak repairs and appears in trouble again while inspecting it. A large part of this is due to the service practices used by technicians who previously worked on the system. The guy that did not flow nitrogen and partially clogged the TXV screen causing the first compressor replacement to fail again in 18 months by starving and overheating the compressor. The second guy replaced the compressor again, properly diagnosed that the expansion valve was not working properly and replaced it as well. The valve however took an extra couple of hours so he evacuated the system for 10 minutes with no micron gauge and what do you know! 14 months later the unit has a burnout! My point is always use good practices whenever possible; just because it's working when you leave doesn't mean that you did it right. The first rule-do no harm.

  6. #6
    Join Date
    May 2004
    Posts
    475
    Try it on some scrap pieces, with and without nitrogen.
    I think you'll be surprised.

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