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I just got a new furnace and a/c. A/C ran fine all summer, but we just had to run the furnace for an extended period over Thanksgiving for the first time since we purchased it. The ceilings and wall are drenched. Ive tried several things, but am getting it in every room of the house. I've already checked the roof for leaks and confirmed everything (furnace, dryer, etc) are venting outside properly. I checked the humidity in the rooms for a day and it ran consistenty between 88% and 91%. It's ruining the walls and ceilings and developing mildew every few hours. I clean and dry it at least twice a day. Any ideas what can be causing this? I don't have a humidifier. This is quickly becoming an urgent issue.
 

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Maddog, I've been keeping an eye on your thread hoping to learn the answer to your problem. Pretty amazing that no one's chimed in. Did you find the cause and a good solution?
 

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Hi Maddog. I made a comment at diychatroom the other week. Ironically, our local home columnist made this comment over the weekend:

"Don't burn unvented gas logs more than an hour or two at a time. Gas logs produce lots of moisture, so if you see water condensing on windows, turn the logs off and crack a door or window. Never go to bed and leave them burning"

Do you have an unvented gas fireplace?

must cite my source:
http://www.charlotte.com/mld/charlotte/living/columnists/allen_norwood/10445994.htm
 

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I've been waiting for Doc to check in. I've never heard of such a problem and am trying to figure out where all of that humidity could come from. This time of year lack of humidity is usually the problem.
 

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I have seen it but have no answer/idea myself. :( That much moisture you would think he had a spring in his basement/crawlspace or something. Actually it leads me another possible idea. Do you have a hot tub/jaccuzi in a room attached to your home??
 

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Hi Maddog,

Try checking the drain pan on the unit, make sure it is not clogged up and holding water in there...

Good Luck and keep us posted,

Scott
 

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Something is very wrong here and I'm beginning to think plumbing.No guesses so far are adding up to 90% humidity range.
 

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If you had a plumbing leak that was infiltrating into duct work that would contribute substantial humidity. I don't know about 90% though. And I would think that you'd start to see moisture elsewhere directly from the leak.
 

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Hi,

There are many furnace/venting related issues that may lead to moisture buildup within the walls. The first thing i would be looking towards is a positive pressure buildup in the home. The positive pressure will force the warm air through poorly sealed areas, in the walls and ceilings, and based on outdoor temperatures, will produce condensation.

Does the furnace have a variable speed blower, and if so, was the blower speed set to the correct setting to produce a reasonably balanced air flow in the home?

How well are the walls and ceiling sealed with a vapour barrier?

Does the home have a return air system?

How well is the attic space insulated and ventilated?

Poorly balanced air systems can affect infiltration or exfiltration rates, and, consequently, it can affect indoor humidity, the direction of moisture migration and the rate of moisture migration. In winter, condensation occurs if the dewpoint of the indoor air is higher than the temperature of an exposed surface or a concealed surface.

Check the blower speed!!

Good luck,
A
 

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:confused: Greetings,

Do you have a humidifier? Possibly a bad humidistat, #50 relay or sail switch that allows the humidifier to run constantly dumping moisture into the duct work to be delivered throughout the house when the main blower energizes. Good Luck :)
 

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If your humidity readings are correct, then it should be easy for a technician to find were the excess is coming in from. I would take a look at your basement concrete flooring. Does it feel damp? Check your local yellow pages for contractors that inspect and repair for damp basements if that is the case. Bob.
 

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If there is a humidistat on this unit make sure it is set for 35-45 %RH. anything more will add to much moisture to the air. Another problem is that a poorly insulated home will have colder exterior walls allowing for condensation to accumulate easier than better insulated walls. A vent free fire place doesn't produce moisture. The moisture in the air was always there however by heating the air up you are making it "thirstier" absorbing moisture until saturated, at this point the dew point is changed and then condensing and a surface area that normally wouldn't allow condensation (psychametrics chart). If there is a humidifier have the circiut tested for a closed contact swich at the #50 relay, the sail switch (old school s688) or humidistat. check to see if the furnace module is wired to the circuit and check to see if it is proper. Or have the by pass damper adjusted. There can also be a water problem in the house not related to the furnace but compounded by it.
Here's a stretch.....check to see if the A/C wiring is correct and that it isn't running in the winter. this would freeze the coil adding this moisture.
:Thumbs:
 
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