Duct condensation again?

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Billbill84

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Hi all.
Not sure how or where to ask this question because it may apply across different topics or crafts.
Last summer I had a ton of condensing on my unit and the trunk in the fully finished basement and after installing 2 70pt dehu's I got the RH to about 30-35% and condensation was greatly reduced. Also had low refrigerant so I'm sure that didn't help. However still had some sweating on the plenum itself but I attributed that, at the time, to the low refrigerant issue.
After a recharge last summer and dehu's running sweating on trunk was gone but still had some on the plenum. I was able to live with that.
Fast forward into winter, I had a pedestal type large humidifier running on the main floor and maintained at 30-35% all winter no issues except during the first month or so, had condensation on bottoms of all windows. After a month that randomly stopped.
Here we are again it's cooling season and AC is on. Absolutely NO sweating on the plenum or unit or the trunk except at the very FAR end of trunk about 15ft away from the AC unit where the AC rooms door is at as you enter the main basement area.
Since my dehu's been running full blast for last week or so, the RH in the basement hasn't dropped below 40%, so that tells me there's much more humidity in the basement at the start of THIS cooling season.

Questions:
1) I'm sort of think the same phenomena is going on when the heating season started with lots of window sweating for only about first month, then sorta stops. Could all that humidifying I was doing in the winter be showing itself now that cooling season is here? Remember no sweating on the actual unit just a small area in the doorway between the AC unit room and the main basement area. See pic
 

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Sparky617

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The humidifying you did in the winter would have been removed in fairly short order by your dehumidifier. The windows sweating in winter are because the glass is cold and the humidity in your air is condensing on the glass. Keeping the air circulating around the windows will help.

I would think this is an air circulation problem in your basement coupled with high humidity. Are your basement walls exposed concrete or concrete block? If so, you might want to do a test at several spots around the basement. Tape a piece of aluminum foil on the wall sealing all four sides. If after a few days you have water condensed on the room side of the foil you have high humidity in the room. If it is wet between the foil and the wall, you have water vapor coming into the room in that spot. Check several spots around the basement. If you have vapor coming in around the basement you could seal the inside of the walls with DryLoc paint or Thoroseal. I'd also make sure your gutters are directed away from the house to reduce the water directly against the house.
 

Billbill84

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The humidifying you did in the winter would have been removed in fairly short order by your dehumidifier. The windows sweating in winter are because the glass is cold and the humidity in your air is condensing on the glass. Keeping the air circulating around the windows will help.

I would think this is an air circulation problem in your basement coupled with high humidity. Are your basement walls exposed concrete or concrete block? If so, you might want to do a test at several spots around the basement. Tape a piece of aluminum foil on the wall sealing all four sides. If after a few days you have water condensed on the room side of the foil you have high humidity in the room. If it is wet between the foil and the wall, you have water vapor coming into the room in that spot. Check several spots around the basement. If you have vapor coming in around the basement you could seal the inside of the walls with DryLoc paint or Thoroseal. I'd also make sure your gutters are directed away from the house to reduce the water directly against the house.
Hey bud thanks for chiming in. I don't have exposed walls it's a finisher basement with poured concrete walls back there. The sweating seems to have stopped and the basement RH is still about 35%. I didn't do anything and that's what's weird. I'll dehumidify all summer long then see condensation first heat, cook house all winter long then see condensation first cool on basement duct. Weird
 

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