Results 1 to 12 of 12
  1. #1
    Was in the stoop space below my house checking things out to see if there was anything going on that needed addressing. During my inspection I found the duct that leads to the front floor register for this level appeared to be completely full of water in the insulation jacket (it's flex ducting suspended from the floor joists). I am at a loss to explain it. This duct is probably both the longest and lowest unit in the house and it is at least 4 feet off the floor (dirt) of the stoop space. There was no standing water in the stoop space.

    Can this just be a case of condensation? If so can I prevent it some how in the future? We live in the south so high humidity is a fact of life as well as running the air a good bit in the summer not only to cool the home but also to dry it out some. The ductwork in the stoop space is below the level of the air exchanger in the garage, is this a possible problem? Should I call a contractor to come examine the system?

  2. #2
    Join Date
    Apr 2003
    Location
    California
    Posts
    634
    most likely condensation, check your drain lines and see if they are clear...

  3. #3
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428

    Origin of Condensation

    Originally posted by dave82323
    most likely condensation, check your drain lines and see if they are clear...
    1. Condensate Drains clear__?
    2. Does Air Hanlder drain for
    1 or 2 minutes when A/C stops?
    3. Secondary Pan problems___?
    4. Are ALL the ducts sealed_?
    5. Proper air flow__________?
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  4. #4
    Thanks everyone. I went down there again today and just for safety(dont want mold) cut it out and replaced that segment. the inside of the ducts was dry so it appears to have just been in the insulation jacket. Will have to wait and see.

    Dan, the condensate drain runs the whole time the unit runs and drips for probably close to 2 minutes after the unit stops. I've often wondered if the drain 'trap' that installed is too deep. Its about 4" tall drop on the A/C side and about a 3" rise on the outside drain side. Maybe I'll have a PM and see if whomever comees out can replace it with something shallower.

  5. #5
    Join Date
    Apr 2002
    Location
    Western piedmont of Carolinas
    Posts
    1,683
    I came across the same senario when checking out the install on my parents new unit. they complained that their floor was warping under one of the baseboard regesters. Crawled under house to find that none of the boots were insulated. Several of the flex runs were saturated with water. Insulated boots, no more condensation.

  6. #6
    Join Date
    Apr 2005
    Posts
    36

    Talking You're missing some basic thermodynamic prinicples

    The reason flex duct jacket and insulation fills up with water has nothing to do with the condensate drain or evaporator coils, unless something is badly tilted and poor ductwork runs allow water from a condensate pan to actually drain into the ductwork (i've seen this before).

    The problem is one of dew points. Most people with crawlspaces have foundation vents which are supposed to allow the crawlspace to dry out. However, the air does not move out of the crawlspace from those vents, it generally moves from outside under the house. As it does the hot, humid outside air cools off to the crawlspace temperature. As the moisture laden outdoor air cools, the moisture has to go somewhere and it condensates on the coldest material it can find first, namely the ductwork. Since flex duct jackets are generally seamless the water that condensates at the higher points saturates the fiberglass within, and drains down to the lowest point. As that lowest point gets heavier as it fills up with water, it gets lower and lower until it usually pulls off the boot and/or the takeoff and falls on the ground.

    Therefore, Flex under a house is genrally a bad idea. Metal duct sealed with mastic and with well attached ductwrap is a much better idea. Not that condensation won't happen, but at least it takes longer for the duct to rust and fall off the bottom of the house than it does for flex to fill up with water and get pulled off.

    The better sealed your ductwork is under the house, the slower this process happens because the dew point temperature is lower if you aren't air conditioning your crawlspace with alot of duct leakage.


  7. #7
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    Originally posted by mlock
    I came across the same senario when checking out the install on my parents new unit. they complained that their floor was warping under one of the baseboard regesters. Crawled under house to find that none of the boots were insulated. Several of the flex runs were saturated with water. Insulated boots, no more condensation.
    I've seen this 1000 times...
    How tall are you Private???!!!!

  8. #8
    Join Date
    Nov 2000
    Location
    Upstate, SC
    Posts
    2,920
    I vote for uninsulated or improperly insulated boots too. The boots sweat and the insulation works like a sponge to soak it up. We have had lots of rain around here the past few weeks to go along with our southern humidity we have this time of year anyway, and we are seeing a good bit of wet flex duct.

    Bobby

  9. #9
    Join Date
    Sep 2002
    Location
    Virginia
    Posts
    3,328
    Hmm ... I was lurking under my own house and found a few flex duct runs with a good amount of water in the insualation as well .

    Im wondering if I should replace the runs , or cut slits in the outter silver lining and hope it dries out ...

  10. #10
    Join Date
    Feb 2005
    Location
    Toms River, NJ
    Posts
    428
    The news just published an interesting article that talks about this problem. It appears in the October 10, 2005 issue, page 20 entitled "The case of the water-filled ducts" check it out


    Dave in NJ

  11. #11
    Join Date
    Sep 2002
    Location
    Virginia
    Posts
    3,328
    i see the newsletter on top of the main page .... but i dont see any other " pages " to be viewed besides the 3 articles they have there .

    You have a link ?

  12. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,639
    Insulated flex duct with a perfect air seal to the high dew point air, will not allow humid crawlspace air to contact the inner cold duct surface. Now we are left with condensation on the joist and bottom of the floor. The moisture cupps the the floor and migrates into the home causing high humidity. The total solution is to put plastic on the earth and close the outside vents. The crawlspace will have the same dew point as the home. During normal-high a/c load, the home/crawl will have of dew point <50^F, which means "no condensation" on the materials in the crawl and comfortable humidity. During low/no a/c load conditions, there is little or no dehumidification from the a/c. Outside humidity steadily infiltrates the home/crawl plus occupants add humidity causing the inside dew points to be higher than outside. Suggest a 100 pint per day dehumidifier to maintain ideal dry conditions (<50%RH or <50^F dew point)throughout the 2,500 sqft home/crawl during cool weather. For you folks that believe overcooling will control humidity, here's your chance to prove it. As the ducts get colder from over-cooling, a lower dew point is required to avoid condensation. As the in-home temperatures drop below outdoor dew points, condensation on the exterior drywall may cause mold growth. Better and more energy efficient to avoid lowering inside temperatures but lower inside %RH with a dehumidifier. Dehu peddler TB

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