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  1. #27
    Join Date
    Apr 2002
    Posts
    11,808
    Air handler is in attic, it is not sweating but the ducts are.

    The coldest thing in that attic will be the air handler casing just down stream of the coil. If anything is going to sweat it is going to be that.

    It is a duct insulation/vapour barrier problem and or duct sealing problem as far as I can tell without being there.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  2. #28
    Join Date
    Apr 2002
    Posts
    11,808
    Fix the duct problem and put the blower back on its proper speeds.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  3. #29
    Join Date
    Oct 2001
    Location
    Waterford Michigan
    Posts
    2,668
    Originally posted by beachwalker
    I have received lots of good info from this forum regarding my sweating duct problems with my two new Lennox high efficiency var spd air handler & 2 spd compressor heat pumps.

    I am considering replacing the existing duct insulation and want to know if anyone has a link to software that can tell me, based on ambient attic temp and relative humidity, how much fiberglass duct wrap would be needed to eliminate condensation? Seems to me there must be a calculator out there somewhere.

    Thanks.
    R=TD/15

  4. #30

    Lightbulb Insulation

    it would appear to me mor so than poor insulation is leakage in the duct system. Such as the gores on elbows, connector, start collars etc. I would concentrate on sealing these 1st. If your area of humidy is high you may require in addition to insulation a vapor barrier. I suspect if you are in an ara of hig huidy there are insulation company that perform this service proffesioanlly. I have seen some pretty nice viynal wrapped duct systems residentially in the easern part of Texas when I visited . Really looked nice almost like a heat wrapp job or something, all seamed nicely and tight no breach in the vapor barrier . Most important is those air leaks... Doesn't seem liek a lot to worry about but it is most likely your biggest problem at this time.
    AllTemp Heating & Cooling

  5. #31
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    1500 cfms on high and low,that's not acceptable ,IMHO.You are losing the benifits of dehumidification.

    Having you insulate or condition the attic,although it will likely solve the problem,I question if it's needed,to stop the sweatig?

    Ducts ,as stated are likely the problem.

    Did the check and record the supply and return static?If the air handler is horizontial,a high return static will often "pull" water off the coil,blowing it into the ducts.

    Your old air handler ,likely didn't have the static capability to do this ,but the VS fan does.

    So if raising the cfm doesn't solve the problem,I'd have the static checked,above .3 on the return ,can be a problem.

  6. #32
    Join Date
    Apr 2002
    Posts
    11,808
    Dash

    As an observation, with some high static and in particular, a high return static, they will pull moisute off of a coil.

    In fact, the first time I saw this happen was with horizontal Carrier VS AHUs. What made this worse was they converted the air flow handing of the Carriers, but did not make a baffle change at the 'point' of the A coil.

    But, this carried over moisture, in the horizontal air handler, would also soak the insualtion in the bottom of the cabinet, and the AHU would be sweating like crazy.

    No condensation on this AHU speaks volumes to me.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  7. #33
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    We have had them sweat ,in the cabinet,duct,or both.

    Just remembered ,there can be a problem ,when turning the A-coil,wher the water blows off the top of the A,Those maybe the ones that carry a mist thru the blower and into the duct.

    Yes,if it was backing up water in the pan and over flowing,the cabinet would be soaked.


    This problem,at least with Carrier ,is more prevalent in humid climates,with Ft Meyers,FL,being named the worst.

  8. #34
    Join Date
    Apr 2002
    Posts
    11,808
    These were the ones that when you converted them to flow the opposite handing, you had to remove the plate on the top of the A and flip a baffle around. They were never properly converted.

    FK4N maybe,don't have a catalog any more.

    I honestly hate AHUs in the attic, and the variable speed ones can run the coldest and be the most prone to sweating.

    I got the Fort Laud/Meyers humidity and then some
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  9. #35
    Carnak & Dash:

    You're both right on.... the first air handler did not have the baffles changed over... so water missed the pan and soaked the insulation... and it rained under the air handler. Contractor replaced the air handler, now it doesn't sweat, which as Carnak says, speaks volumes.

    Condensation has lessened on 1500 cfm setting, but I agree, loss of humidity control is not acceptable. As a test I am going to replace a 4' section of duct insulation and put everything back to the original cfms and enable humidity control (low stage compressor & 70% cooling cfm's) to see if that will stop it.

    The bigger bullet to swallow is the garage because I will have to pull off a lot of sheetrock to get to the ducts.

    Thanks, again, to everyone. You've been a big help.


  10. #36
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by prodiyer
    I dont use a calculator, I do the math myself. NORMCHRIS WHAT DO YOU WANT A COOKIE !
    So, you can't do the math, yourself, there, scooter, and are jealous?

    Just ask, we'll teach ya.

    No need to make your ignorance shine so brightly in front of everyone.

  11. #37
    Originally posted by condenseddave
    Originally posted by prodiyer
    I dont use a calculator, I do the math myself. NORMCHRIS WHAT DO YOU WANT A COOKIE !
    So, you can't do the math, yourself, there, scooter, and are jealous?

    Just ask, we'll teach ya.

    No need to make your ignorance shine so brightly in front of everyone.
    I thought the same thing Dave... Typical of someone who is new here and doesn't care to learn about the site and it's members before acting like an idiot. Kudos to Norm for letting it slide, I don't think I would have been able to.

  12. #38
    Join Date
    Apr 2002
    Posts
    11,808
    prodiyer sure sounds like eddy, was awaiting to see norm's math tho
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  13. #39
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,272

    Exclamation New Concepts ?

    Originally posted by beachwalker
    Thanks... According to their meter, relative humidity in the attic was 100 % this morning and temp was 101.

    Any thoughts on these ideas?
    ALTERNATE R & D:

    Could I get your Attic SPECS
    so that I can develop and copyright a Cheap SAUNA?
    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

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