Condensation from AC


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Old 07-09-02, 07:56 AM
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Condensation from AC

It has been very hot the last week in my area so the AC has been getting its workout. I noticed the other night in my basement that the duct work had some condensation on it and was dripping on the floor. It seemed to be within a couple feet of my blower on the duct and formed on the sides and ran down. Now this is not to big of a deal right now but will be in the short future because I am in the process of finishing my basement. Is there anything I can do to keep this from happening - short of turning off my AC? Is there any type of wrap or will insulation help once I have finished my basement?

Any advice\suggestions are greatly appreciated. Thanks.
 
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Old 07-09-02, 03:08 PM
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duct

is not insulated properly, get some duct wrap on it before putting up the cieling, it will be much easier.
 
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Old 08-08-02, 10:47 AM
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I got to looking at this closer a week or so ago and discovered that it is not the ductwork. The water I see dripping down from the duct work is coming from directly above on the underside of the main floor. let me try to give layout of this and may be someone could give me some help.

The problem is confined to a small area, between 2 floor joist and about 3.5-4 feet long. You can see the wet spot start\stop and between the floor joist to either side is no wet. I can see water beading up on the underside of the main floor. Directly below the floor joist is my ductwork(AC & heat) and the ductwork is about 1-1.5 feet wide. Then about 4 inches to the side of my ductwork is my cold air return and it narrows right from about 1 foot to a half foot. Both the ductwork and cold air return are running perpendicular to the floor joist and are about 3-4 feet away from my blower. There are no water pipes anywhere close and directly above is my living room where my coffee table sits - there have been no big spills there either. I assume this is condensation but why just in this one spot and how do I fix. Also there is some mold starting to grow on the floor joist where the wet spot is - how should I clean this up?

Thanks any advice.
 
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Old 08-08-02, 02:15 PM
bigjohn
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Am I correct in assuming that the furnace is in the basement and not above the area where the wet spot is? It sounds like the supply duct may be leaking some cold air at that spot and it's hitting the warmer wood above. Can you reach your hand up in there or maybe sneak in a piece of paper glued or stapled to a stick and see if the paper blows around??
 
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Old 08-08-02, 02:55 PM
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Your assumption is correct about the unit in being in the basement. I will check tonight to see if there is any air leaking out a gap\hole. Thanks.
 
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Old 08-09-02, 03:46 PM
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I just check and it does not appear to be a gap or hole in the ductwork. it does look as though there is more condensation above the ductwork rather than cold air return vent.


Any ideas on what I can do to fix it? should I get some ductwork insulation?

Thanks.
 
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Old 08-10-02, 02:35 PM
lynn comstock
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Puzzling.

I thought Bigjohn was on the right track. Is there any water at all above the return duct? (The picture in my mind is not clear on this point.) Also is the heat provided by a warm air furnace? (And not a hot water radient heat system from the floors.)

When you checked for a hole or gap, was the fan and cooling on? Feeling for a cold draft is easier than feeling for a gap or hole.
 
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Old 08-12-02, 07:03 AM
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The cold air return and the ac\heat duct are about 4 inches apart running parallel to each other and run perpendicular to the floor joist above. The water is only between 2 floor joist and above both the cold air return and ac\heat duct - the water is actually above both. I have a forced air unit - no hot water radient heat system.

The ac was on and blowing when I checked the duct and I was not able to feel any air blowing out. Could it be that the temp between the basement air and the ac duct are different enough to cause such a problem?? But at the same time I would think I would see it in other areas. Thanks.
 
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Old 08-12-02, 07:51 AM
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So you're saying that both the supply and return air ducts have moisture on them? If the dew point in the basement was high enough to cause sweating, then the entire uninsulated duct would be sweating. I still think you have a small air leak on the supply duct that's blowing cold air onto the return duct and also onto the flooring and floor joists. Maybe warm outside air is passing over just the area where the ducts are sweating??- that's kind of a reach, especially if you've got a wet spot on the floor above and there's mold on the joist. Check closely where two sections of duct are joined together.
 
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Old 08-12-02, 11:08 AM
lynn comstock
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Try this test.

Test: Blot up the water on the flooring and joists. Lay some duct insulation over each duct (separately) in the problem area. Put the foil or vapor barrier DOWN, between the duct and the insulation. If water is condensing from the air the water will start to drip off of the vapor barrier and the insulation will protect the flooring, which should dry up.

If the flooring continues to drip above the insulation and vapor barrier there has to be another source of water. That is why I asked about the possibility of radiant heating in the flooring above.
 
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Old 09-03-02, 02:37 PM
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Problem Solved

Thanks for all the suggestions. I finally got the guy who installed the unit when the house was built last year to look at it last week. He also was unable to find any wholes in the ducts. What he did figure out was that between the 2 floor joists that was having the problem did not have the insulation pushed all the was up in where the basment wall meets the floor joist. The insulation happened to be pulled out far enough that warm air was coming from behind it right down between the 2 floor joist and over the duct. Once the insualtion was pushed back up the condensation started to dry up immediately. Now all I have to do is wipe the floor joist down with some bleach water to kill the mold. Thanks again everyone.
 
 

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