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  1. #1
    Join Date
    May 2004
    Posts
    26
    This has been a long saga for me with this particular A/C problem. A little background, I live in Houston and last year my A/C was not cooling well. After batteling with my A/C contractor and contacting Trane's technical service line had Trane send two engineers to my house to correct my A/C problems. The long story can be found in this thread. http://hvac-talk.com/vbb/showthread.php?threadid=53101


    Basically, they found too high of static pressure in the system, and contaiments in the refrigerent. The put a liquid line drier on and reconfigured the air intake and pulled a vacumm and recharged the system. A/C ran like a champ the rest of the summer, cooled great....

    My System is
    I have a new home with a Trane XR12 3.5 ton system in a 1722sqft home. The Compressor is 2ttr2042b1000AA the furnace is tue080a948l1 XB80 the coils are TXH041A4hpA2

    The problem. A few weeks ago I came home and noticed that the A/C seemed to have frozen up. The indication I got was frost on the suction line outside, and very low airflow through my vents in the house. I immediately shut down the A/C and the next day bought a new air filter before running the system again. The airfilter that was in there was pretty new (had less then 100 hours of operation on it as monitered by my thermostat I ussually keep them for 200hours) but I thought it might be low air flow so I replaced the airfilter anyway. Additionally, after all of the problems last summer have a thermometer installed in one of the supply vents so I can measure the delta temp between supply and return air. I've been noticing over the last several days that the delta temp is a maximum of 13 degrees F between supply and return last summer it was running 15-22 degrees difference. The A/C now runs for about 30 minutes and gets the about a maximum of a 13 degree difference then the supply vents gradually warm up until the system is just blowing room temp air. The compressor keeps running and the air keeps blowing inside but as it warms up is when I notice the suction line out side at the condensor begins to develop frost. If I turn the A/C off for a few minutes and then back on the A/C will blow cold air initially but after about 30 or so minutes the supply air gradually begins warming up again and the cycle continues. Needless to say if I shut it off and turn it back on it can eventually cool the house but it is a pain. Any ideas? Also the coldest I measured the supply air coming out of the vents is about 62F which seems not cold enough to cause the system to freeze. But its weired it seems to once the supply air starts indicating that its about 75 ish is when I begin to notice that the supply vents air velocity seems to start to diminish could be my mind playing tricks on me?

    Nothing has changed in the house that I'm aware of since A/C season last summer. I've not adjusted the dampers in any of the vents no new tree's etc.

    Thanks in advance for any advice you guys can give me. At this point I want to shoot my A/C! Except I'm poor so I'll settle for fixing it!

  2. #2
    Join Date
    Apr 2003
    Location
    Eugene, Oregon
    Posts
    1,209
    When you notice the frost outside and diminished air flow, check your indoor coil. It's probably frosting and cutting off air flow. This can be caused by low refrigerant charge or poor air flow. Have you had the unit serviced this year? Indoor coil may be plugged. Also, if you have a 90% condensing gas furnace the secondary heat exchanger may be plugged. I don't know Tranes model #'s well, it would appear the XB80 would be an 80% therefore not having a secondary exchanger. Some things to consider. Good luck.
    Proud supporter of Springfield Millers and Oregon Ducks.

  3. #3
    Join Date
    May 2004
    Posts
    26
    Well it was diminished airflow only on the first time I noticed frost (it maybe more oversenstivity too). Now the system dosen't seem to diminish in airflow, just stop cooling after a while. Yes, its an XB80 furnace and its set to the highest blower speed for cooling verified that last year.

    Nope not had the system serviced since last year, and the system is less then 2 years old BTW. I've been very careful to always replace the airfilters with qualty filters often. The coils are in a sealed box and I can't inspect them easily. After all the problems I've had with bad contractors I was hoping to leave it alone this year.....

    Another observation has been when the condensor outside begins to freeze it seems to stop blowing warm air out the top.

    [Edited by jon_99 on 05-10-2005 at 10:02 AM]

  4. #4
    Join Date
    Oct 2004
    Posts
    3,400
    Get somebody out to find and fix your leak.



  5. #5
    Join Date
    May 2002
    Location
    Houston Texas
    Posts
    6,320
    You have a refrigerant leak possibly the coil (least likely) most likely in one of the new joints.
    It could also be possible one of the Schrader valves is leaking. The reason the air diminished the first time was the coil froze up you now are paying such close attention it doesn't have time to freeze.

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