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  1. #1
    Join Date
    Nov 2004
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    Been watching this board for a couple of weeks now. Has been very educational. Now I need some specific help which I'll cover in more than one post. First, a little background: I am a homeowner (Eastern North Carolina) that had a 3-ton split system heat pump installed in a new construction just 5 years ago. It's a bryant R-410A 14 seer unit with a variable speed air handler and the standard themostat ( not the thermidostat ). Airhandler and duct work located in crawlspace of ranch house. A recent inspection revealed that my airhandler has not been draining properly. In fact, water was dripping from the seams, the unit insulation was completely saturated, rust stains on fan and cabinet and a large amount of water carry over into the duct work. In fact a puddle several inches deep and evidence of water trailing was found in the main trunk line coming off the plenumb. Also, the flex duct system and air handler is full of mold growth. I have determined that a shallow trap (insufficient per the installation instructions for a negative pressure system) and a belly in the drain line could be the entire cause. There was no secondary line installed. A factory rep. says that, except for the drain line issues the unit was properly set-up.

    Is it possible that improper drain line set-up completely explains the presence and carry over of excessive moisture and mold inside the unit and duct system?

    One "expert" suggested that compromised duct insulation can cause condensation inside the duct. Others have argued that is not possible. What I know about physical science properties supports the fact that improper insulation of ducts will cause condensation on the exterior of the duct but not on the inside. The duct surface would be warmer where there isn't insulation, discouraging any condensation internally. Isn't it true surfaces need to drop below the dew point for condensation to form? Input please?

    Teddybear, Frank_G, CxAgent-others?

  2. #2
    Join Date
    Aug 2002
    Office and warehouse in both Crystal River & New Port Richey ,FL
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    I've seen older metal ducts systems,with insulation falling off,in attics,that the metal gets moisture on the inside.

    As for the drain,the trap and belly ,could have been the problem.
    I'd check the External Static Pressure of the return duct,if it's over .4" of WC,that could be the problem.The negative pressure on the retun side can prevent drain,is the ducts and/or return grille is undersized.

    It also could have been on the wrong speed,ie set for 3.5 tons of air.

    Post the return duct and grille size,for more input.

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