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  1. #1
    Join Date
    Jul 2007
    Location
    North Little Rock, AR
    Posts
    19

    Weird ductwork sweating issue....

    A friend of mine called me about a strange situation he has with some ductwork. The homeowner noticed all of the insulation on his ductwork in the crawlspace was wet. My friend says that the original tape and insulation job was poor, so he just assumed that this was the cause of the wet insulation. He then proceeded to remove all existing insulation, sealed all joints with mastic tape, and re-insulated all pipe with two inches of foil-back wrap.

    He called me yesterday and said that when he checked on the system again, that there was a light film of condensation forming on the outside of the duct on most of the system. I told him to make sure that he did not have a "lazy air" situation, which he does not, (there is 1550cfm of pipe on a four ton system) there is good velocity out of all the registers. He said there is a moisture barrier on the ground, and that the dirt under that was dry everywhere. Foundation vents were open however.

    This is a house in Little Rock, AR. We have had an enormous amount of rain in the last thirteen months, and it is quite humid here, but he says the ground is dry under the house.

    Any idea why this would be happening? No lazy air problem, no moisture problem (seemingly) under the house.

    Any ideas?


    S

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,910
    High RH in crawlspace, makes for a high DP temp.

    What temp is the insulation surface at while system is running. And what temp and RH is the craw;space at the same time.
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  3. #3
    Join Date
    Jul 2007
    Location
    North Little Rock, AR
    Posts
    19
    Quote Originally Posted by beenthere View Post
    High RH in crawlspace, makes for a high DP temp.

    What temp is the insulation surface at while system is running. And what temp and RH is the craw;space at the same time.
    Great question, I will get him to check that today. I also advised him this morning to check the temp difference in the return and supply, and check the charge of the unit to make sure it is not grossly overcharged. I had assumed he had done that when I made this post, but he at this time has not checked that!

    Oh well, hey thanks for the question. I will let you know what he finds.


    S

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