Weird duct sweating question. Why in this spot?!?

Discussion in 'HVAC' started by Billbill84, Aug 23, 2019.

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  1. Aug 23, 2019 #1

    Billbill84

    Billbill84

    Billbill84

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    Hey guys. Alright I posted about my HVAC issue a few weeks back and had sweating ducts in the basement and after adding a second LG 70pt dehumidifier to my basement in the mechanical room the sweating has stopped except on the air handler itself. So due to this, I will ask my questions in two parts because what's happening isn't making sense.
    1) You'll see in the pics that I've circled the two areas that are sweating a little. One is on the plenum which I think houses the coil but the other sweating duct skips over a non insulated plenum and sweats on the supply that goes straight up thru the upstairs floor and a boxed in area in the corner of the living room and continues up to the attic as it feeds the 2nd level above main level. This one concerns me the most. I got up in the attic and found that this boxed in shaft area in the living room wall, I can see down into it and just see two long vertical ducts, the supply and return. No insulation not even on the top at the end of the run that I'm looking down into from the attic. So the vertical supply is inside a box that's probably hot inside, up to the attic that IS hot. I know there's no air movement in that box and a HVAC guy that services my work's HVAC system said to maybe try to cut out that flat portion of sheet metal and maybe pop a small fan in there and to go back in attic and see if I can glue some foam board to close up the top of the shaft. What are some thoughts on this?
     

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  2. Aug 24, 2019 #2

    nealtw

    nealtw

    nealtw

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    You should not be able to see down that shaft, that should be sealed up tight.
    That shaft is likely supplying air with more moisture back from the upstairs or the attic.
     
  3. Aug 24, 2019 #3

    Billbill84

    Billbill84

    Billbill84

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    What I meant by shaft was just the square boxed in area of sheet rock that the ducts are behind. I'm not sure if I explained it right sorry. Were u referring to the actual supply duct work? I can't see inside any ducts just the top of the boxed in shaft. I attached a pic below to give a clearer picture of the interior of the shaft from the living room with an illustration of how it's built. Are u saying that hot air is being drawn in from the top from the openings up there in attic? It's weird because the supply is sweating just past the floor joists and I can see this from below if u zoom in on the pic in my first post. Please clarify for me if u can, and how in God's name could I stop this?
     

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  4. Aug 25, 2019 #4

    nealtw

    nealtw

    nealtw

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  5. Aug 25, 2019 #5

    Billbill84

    Billbill84

    Billbill84

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    Cool thanks for the video very informative. So u think it's possible that the inside of that shaft could be full of hot moist air from the open end up top in attic and that's why I see sweating way down by the air handler?
     
  6. Aug 25, 2019 #6

    nealtw

    nealtw

    nealtw

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    Yes and that should all be tight in the attic so you don't loose conditioned air up there anyway. Then you could look at just leaks around the vents into that shaft from the rooms upstairs.
     

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