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  1. #1
    Join Date
    Oct 2019
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    The mystery of the liquid line that keeps sweating when everything is off

    Been searching for this kind of behavior for some time now and haven't found something that fits my scenario. Had a new RHEEM 2-ton Central AC unit installed in July. In fact, they installed everything including a new furnace, ducts, etc... Soon after the install, I noticed that the LL was sweating and dripping inside the house for an average of about 10' long every morning. There were days where LL sweating would reach the furnace, approx 20'). This happens even if everything is powered OFF at the breaker (AC unit, furnace, etc...).

    This doesn't seem to happen when the day temp is pretty much the same as the night temp. For instance, outisde temp would be 68+ during the day and if it goes to about 50- during the night then I would definately get the dripping (that is, even if everything remains OFF).

    They came by again and replace the whole AC unit outside. The next day, the problem remains. They have no clue what it is. Since the replacement, I had started the AC for about 5 minutes and noticed that there are huge temperature variations at the filter/drier just before going in the evaporater (furnace). Within a minute, there could be about 6 temperature changes very noticeable just with the hand, going from very cold to very warm/hot, then very cold again, etc...

    So... anything that rings a bell to anyone?

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Inverted P-Trap at the air handler?

  3. #3
    Join Date
    Oct 2019
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    Thread Starter
    Hmm, assuming you are referring to the suction line?

    No, there's no P-trap at the air handler aside from the condensate drain. In fact, the suction line (same for LL) goes straight up for about 6' (no P-trap) and then horizontal for 15' but in a slope towards the evaporator and not the external unit. I've read that the slope should actually be towards to exterior unit (condenser). Does any of this make sense?

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
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    That’s fine.

  5. #5
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    Are you talking temp change in the line between the filter and coil or the line going into the filter?

  6. #6
    Join Date
    Oct 2019
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    Thread Starter
    Both actually, the whole LL goes from very cold to very warm constantly when the AC is running. You can feel the temp changes from the home entry up until the evaporator, the filter is just before the evaporator.

  7. #7
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    This would be due to restriction, upstream of the point where the line is getting cold.
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  8. #8
    Join Date
    Oct 2019
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    Thread Starter
    When the AC is off, it's only about the first 8' into the home that gets sweaty in the morning and it happens only in the morning... when the AC is ON though, it's the whole LL that keeps changing temperature not just a portion of it. I can't say I've checked the suction line though because it is insulated.

  9. #9
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    Does it cool fine or is it short?

    Is this an A/C or heat pump?

  10. #10
    Join Date
    Oct 2019
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    Thread Starter
    Haven't used it all that much but it seemed to work good when we used it. It's just AC, no heat pump.

  11. #11
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    It almost sounds like you have a combination of hot gas and liquid going through the line, which should be all liquid. When the gas goes through it gets warm, then liquid passes, then it boils off creating the cold, then the cycle repeats. If that is what is going on then why. Does the unit/compressor cycle at the same rate as the warming/cooling?

  12. #12
    Join Date
    Oct 2019
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    Thread Starter
    Your explanation totally makes sense to me for the constant change in temperature... and as you said, why?

    How would I know if it cycles at the same rate?

  13. #13
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
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    He means, is the outdoor unit running constantly during this temp change, or does it turn on and off when the line gets hot or cool...
    Last edited by vstech; 10-11-2019 at 05:18 PM.
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