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  1. #1
    Join Date
    Aug 2013
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    Conflicting wiring info

    I had a trane two stage heating/cooling system (XL18i) installed recently and the system is working. The installer however made a mistake in installing the Media Filter Box in reverse resulting in the Media Filter can only be inserted where the arrow on the filter is against the airflow. He is coming to take a look and I hope he will fix this.

    With this mistake, I thought I am going to check all the wiring too as I have heard on forums that they sometimes wire the two stage systems wrong.

    It is about the Y terminals. Outdoor unit documentation says connect Y1 (YL/BK) to Yo and Y2 (YL/RD) to Y2. The Furnace Documentation says connect Y to Y1 (YL/BK) and BK to Y2 (YL/RD). On the Furnace control board I have a YLo,Y,W,W2,R,G,C,O,BK/DS/DHUM

    Current Connections
    Y -->Y -->YL/BK
    Y2 -->YLo -->YL/RD
    B/C-->B/C -->B/C
    R -->R (goes through two float switches in serial before coming to Furnace)
    W1 -->W1
    W2 -->W2
    G -->G

    So based on diagram looks like Y2 instead of being connected to YLo on the furnace side should be connected to BK and to YL/BK on condenser, is this correct or is the current wiring OK ?

    When asked how to determine what stage coolling is currently running I was told that you cannot tell as it is all automatic between single stage and second stage.

    I purchased two stage cooling for excessive humidity problem and I want to make sure I am running first stage cooling most of the time.


  2. #2
    Join Date
    Aug 2003
    Fort Worth, TX
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    Two ways you can tell if a two stage system is able to cycle between stages are:

    1) Indoor blower speed should change between stages: slower speed in first stage and higher speed in second stage. The change in speed, unless your blower is really quiet, should be noticable.

    2) If the outdoor condenser uses a Copeland Ultratech scroll compressor, it will sound different in second stage vs. first. The compressor sound in second stage is more sounds like it is under a higher load. It should also be a little louder. In first stage the steady buzz is softer and less loud. If you have some other type of compressor setup (two compressors or, God forbid, a reversing reciprocating compressor), there still should be some sort of sound difference between first and second stage.
    Building Physics Rule #1: Hot flows to cold.

    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure

    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

  3. #3
    Join Date
    Aug 2013
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    Thread Starter
    Thanks for that suggestion and that is what I tried doing but not able to tell any difference. I used the test mode on the Honeywell TStat and switched the first stage on, went out and listened, then had my wife change the test mode to activate the second stage but could not tell any difference in the compressor running. Is it possible that it is always running at second stage.

    By the way it is a trane 4TTX8048A1000A condenser, TUD2C080A9V4VB furnace and 4TXFH054CC3HHB slab coil.

    I just want to make sure my setup is wired correctly for two stage cooling.

  4. #4
    Join Date
    Feb 2009
    Tallahassee, FL
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    How about the air handler? Does the fan slow down significant with lo stage.

    Its hard to tell the difference on the outdoor unit by just listening ...however I can personally hear the difference.

    I recommend a skilled tech to review the wiring and take a amp draw at outdoor unit to verify it shifts to low stage.

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