Moisture Dripping from crawl space ducts

Problems related to residential installations.

Moisture Dripping from crawl space ducts

Postby NCMau3839 » Wed Jul 27, 2016 12:00 pm

I was checking the crawl space few days ago and I noticed some ducts dripping moisture to the point that some small puddle of water were collected on the ground. The crawl space is 1500 sq ft, two feet high with plastic applied everywhere on the ground. All perimeter vents are closed and there is no musty odor. Of course, these days with triple digit heat index temperature and high humidity may have caused this situation. I haven’t noticed it until now, but it doesn’t mean that it did not exists before.
The 9 year old heat pump is a 3-ton package unit and the duct work is all flexible. The system appears to be operating very normal.
The recent consensus is that a crawl space should have plastic applied to the dirt floor and all vents should be be closed. There is no ventilation. I am sure that whoever conceived this idea know a lot more than I do on the subject, but I just can’t help to believe that ventilation would be helpful in preventing this condensation.
What would be a practical solution, fan, dehumidifier, open the vents during the summer or leave it alone?
Please share some of your thoughts.
NCMau3839
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- Moisture Dripping from crawl space ducts

Postby Freon » Thu Jul 28, 2016 3:07 pm

Keeping the crawl space as it is now, in my opinion, is the best way. Your goal is to make the crawl space as dry as possible and outside air is saturated these days.

As to the water, can you feel any condensation on the outside of the flex duct? Are the puddles under where supply registers are located or are the puddles randomly distributed? Are the puddles only on the supply lines (cold air to the house) or ar there puddles on return lines bringing air back to the air handler?

Two possibilities occur to me. One, given the very high humidity in your area, the evaporator coil is so wet that the air flow is actually blowing some of the condensation from the coil into the supply ducts. If you can access the supply plenum you can see if this is the case.

The other possibility is a clogged drain n the pan under the evaporator causing the condensate to overflow into the return ducts. However there is usually a float switch to prevent this from happening.
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- Moisture Dripping from crawl space ducts

Postby NCMau3839 » Tue Nov 15, 2016 6:31 pm

Freon, I want to thank you for the response and because of health issues I was not able to get back to this post. I apologize. I went under the house and assess the situation again and now being the heating season, there are no water puddles on the ground.

What I did noticed, however, the supply flex right out of the package unit is filled of water. The water must have been there for long time and caused the moisture and condensation to travel thru the flex system. I pocked a small hole at the bottom of the flex where the water is accumulated and it is now being drained.

The supply flex out of the package unit is routed under beam, causing the dip to be almost a foot below ground level. I am not so sure that this is proper installation, but given the situation, I don’t know if there is an alternative. Maybe eliminating portion of the beam, or fabricate a special plenum to reroute the flex?

If the flex has to stay where it is, would the water always be an issue? I don’t know how long this water has been there but I suspect few years. I just didn’t see it before.

I hope there is an easy solution. I have a unexpired 10 year warranty on the package unit but I am not sure it covers the duct system too. I have to check on it and I surely going to bring up to their attention if it is not a proper installation procedure.
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- Moisture Dripping from crawl space ducts

Postby Freon » Tue Nov 15, 2016 8:22 pm

You need to determine where the water is coming from. Many times it is condensation on the evaporator coil blowing off into the supply duct. Not knowing the physical setup I can't say for sure. But find where the water is coming from
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