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Thread: LONG RUN TIMES Trane XR17 4TTR7048A1000AA 4ton Trand XL824 T-stat

  1. #1
    Join Date
    Apr 2018
    Location
    Kenedy, TX
    Posts
    9

    Default LONG RUN TIMES Trane XR17 4TTR7048A1000AA 4ton Trand XL824 T-stat

    Model Number: 4TTR7048A1000
    Brand: -major brand-
    Age: 1-5 years

    House is new construction with sprayed-in foam insulation, 2550SF, 10ft ceilings. Built by well known Texas builder and occupied in December 2015. All the HVAC equipment is presently TRANE. (Original thermostat was a Honeywell)

    HISTORY:
    07/21/16 HVAC contractor returned to properly wire the ERV. Added 2lb refrigerant.
    12/09/16 HVAC contractor responded to warranty service call and and found T-stat control board would not complete call for Heat.
    Replaced T-stat and control board with another Honeywell (2nd)
    08/31/17 HVAC contractor responded to warranty service call for Long Run Times. Found low charge; added an unknown amount of refrigerant.
    09/13/17 HVAC contractor responded to warranty service call for Long Run Times. Replaced T-stat and control board with another Honeywell.
    (3rd)
    10/13/17 HVAC contractor responded to warranty service call for Long Run Times. Replaced Honeywell with TRANE (free "upgrade") (4th t-stat)

    We run a Day/Night schedule on the thermostat with the Day set point of 77deg from 0600 to 2200hrs. The Night set point is 73deg from 2200 to 0600hrs. We have three small digital thermometers around the house that are withing a few tenths of a degree apart that we use to determine the house temperature.

    During 100+deg days here in South Texas, the unit has no problem maintaining the indoor temperature of 77deg with minimum run time.
    At night when the set point changes to 73deg the unit rapidly cools the house to 73deg. Beginning around 11 June, the compressor continues to run long after the set point temp is reached. Generally the unit will run for 45 minutes, stop for 3 to 7 minutes then start up again. The indicated temp on the thermostat never changes from the set point of 73deg.
    This week, during the rainy weather brought on by the tropical low in our area, the outside temps have been around 77deg, only a few degrees above the indoor set point. The unit continues to run most of the night except the 2-stage compress sounds like it is running at low speed and the variable speed fan is running at a low setting. But the unit continues to run most of the night.

    I have tried setting the night temp manually but there was no change. I have changed the Setpoint Deadband from 3deg to 6deg to no avail. I have changed the operation from COOL to AUTO to no avail.

    The system works perfectly all day but runs continuously at night, when it's significantly cooler. Can anything other than the T-stat signal the compress to start? How can a thermostat signal the compressor to start when the house temperature is at the set point?

    If this is another T-stat failure, is there any way I can use a stone-hammer simple Honeywell RTH6350D thermostat to run this unit?

    Any anecdotes, advice, suggestions or opinions will be gratefully accepted.

  2. #2
    Join Date
    Apr 2018
    Location
    Kenedy, TX
    Posts
    9

    Default

    FOLLOW UP

    The Home Builder's Warranty Dept. contacted the HVAC contractor who contacted me Monday and advised that there was a TRANE bulletin out regarding TXV malfunctions. They arrived today and changed the TXV and added a small amount of some kind of lubricant to the refrigerant line. Apparently the "bad" TXV was stuck half open/closed.
    So far, so good but the bulletin recommends waiting 48hrs to assure normal functioning.

    After looking up "TRANE TXV" online I discovered that this problem has been around awhile. Interesting reading.

    MaxNR

  3. #3
    Join Date
    Aug 2004
    Location
    McMullen Valley, Arizona
    Posts
    92,268

    Default

    Thanks Max for the update!

    That will help others.

    HVAC isn't my specialty or I would have responded to your thread earlier, but other HVAC techs may come in here and see it.

    Jake
    Appliance Repair School 1987-1988
    Star Appliance Tech. 2 yrs. 1988-1990
    Wards Appliance Tech. 11 yrs. 1990-2001
    Sears Appliance Tech. 4 yrs. 2001-Oct. 2005
    Jake's Appliance Repair Nov. 2005-present

    Look-Up & Order Parts

  4. #4
    Join Date
    Apr 2018
    Location
    Kenedy, TX
    Posts
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    Thanks Jake.

    I'll update this again in about a week.
    Here are links to some of what I found on the web:

    https://www.meloair.net/blog-1/trane...g-txv-failures
    https://www.meloair.net/blog-1/this-...pansion-valves
    https://www.meloair.net/blog-1/new-i...d-txv-failures


    MaxNR

  5. #5
    Join Date
    Aug 2004
    Location
    McMullen Valley, Arizona
    Posts
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    Default

    Thanks Max.

    Yes, please keep us posted.

    Jake
    Appliance Repair School 1987-1988
    Star Appliance Tech. 2 yrs. 1988-1990
    Wards Appliance Tech. 11 yrs. 1990-2001
    Sears Appliance Tech. 4 yrs. 2001-Oct. 2005
    Jake's Appliance Repair Nov. 2005-present

    Look-Up & Order Parts

  6. #6
    Join Date
    Apr 2018
    Location
    Kenedy, TX
    Posts
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    Post TXV replacement Update:

    The A/C system has been up and running with the new TXV for just less than 48hrs now. I think it IS more efficient now as it is running only 16-20 minute cycles at night instead of the previous 40-45 minutes but still pauses only 5 to 7 minutes between cycles. As before, this continues all night long.

    Running the same schedule as in my first post the house cools from 77 deg to 73 deg in about an hour. By 2300h the inside temp was 73deg, the reported Outside Air Temp (OAT) was 78deg and Relative Humidity was 48%.

    At 0330h this morning the inside temp was at the setpoint, 73deg with an OAT of 75deg and RH of 45%. With only three degrees difference between inside and outside temp, I cannot understand what is causing the system to continue to cycle all night at such a frequent rate.

    I turned the A/C OFF at 0330h. By 0700h this morning the Inside temp was 76deg, the OAT was 78deg and RH 48%. Both inside and outside temps rose 3deg.
    Is this an excessive increase in temperature inside a house with foam insulation??

    Finally, a question regarding "Setpoint Deadband": If it is set a 3deg, does that allow a +/-3deg deviation from setpoint? or +/-1.5deg deviation??
    As stated in the first post, I tried changing the Deadband from 3deg to 6deg but there was no change in the nighttime behavior of the system.

    Any and all comments, anecdotes or suggestions are welcome.

    MaxNR

  7. #7
    Join Date
    Aug 2004
    Location
    McMullen Valley, Arizona
    Posts
    92,268

    Default

    Thanks Max,

    I turned the A/C OFF at 0330h. By 0700h this morning the Inside temp was 76deg, the OAT was 78deg and RH 48%. Both inside and outside temps rose 3deg.
    Is this an excessive increase in temperature inside a house with foam insulation??

    Finally, a question regarding "Setpoint Deadband": If it is set a 3deg, does that allow a +/-3deg deviation from setpoint? or +/-1.5deg deviation??
    As stated in the first post, I tried changing the Deadband from 3deg to 6deg but there was no change in the nighttime behavior of the system.
    I have no clue myself, but hopefully another tech. that specializes in HVAC can tell you.

    Jake
    Appliance Repair School 1987-1988
    Star Appliance Tech. 2 yrs. 1988-1990
    Wards Appliance Tech. 11 yrs. 1990-2001
    Sears Appliance Tech. 4 yrs. 2001-Oct. 2005
    Jake's Appliance Repair Nov. 2005-present

    Look-Up & Order Parts

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