Condensation from air vents.

[arod0422]

Hello All,

I had a new AC unit ( 5 ton) put in a couple months ago (inside and outside unit).
About a month in i started noticing condensation from 2 small vents one in a bathroom and one in a closet. None of the other vents trough out the house have this issue. The humidity in the house is consistently over 65%. Was never over 60 with the 12 yr old unit.

I've gone in the attic and made sure the lines coming to these vents were properly insulated and had no tears or leaks.
The unit itself looks to be sealed perfectly. and the house cools nicely.

Not sure what could be the problem here. and why its only in these two place

Any ideas

 

[Fitter30]

RH has to be below 50% in cooling. Above can grow mold. Was some duct changes made? Size of unit changed? House close to Miami? Call the electric company see if they offer a energy audit that includes a blower door test or who to call. You tube has some videos on he test.

 

[Sponsor]

 

[arod0422]

Yea im in miami. And its hot as hell here.
No duct changes were made. Same size unit i had before. I do feel like this new unit blows alot harder than the old one.

I do have a bathroom project going and one of the walls is an outside wall that has insulation but no sheet rock on right now. Could that be a contributing factor?

 

[Fitter30]

Yea im in miami. And its hot as hell here.
No duct changes were made. Same size unit i had before. I do feel like this new unit blows alot harder than the old one.

I do have a bathroom project going and one of the walls is an outside wall that has insulation but no sheet rock on right now. Could that be a contributing factor?

Need a probe style thermometer not a ir. After unit runs for at least 20 minutes need to take temps at filter rack and 18-24 " from the evaporator. Will have to drill a hole in the duct for a temp reading. Want to know the temp difference. The duct in the closet and bath are probably not sealed and hot air is entering from attic. Have you look up at grill and its dirty and ceiling around it ? That's not from the air blowing out but dirt in the air getting picked up by terbulence from the air air the grill picking up the warm air around it and sweating.

 

[arod0422]

Yes grill and the ceiling show signs of dirt. I had been in the attic and sealed it best I could a couple weeks ago but that didnt help

 

[Fitter30]

Call your electric company see if that offer a energy audit that includes a blower door test. This test tells how tight the house is. You tube has videos of the test.

 

[arod0422]

Im going to look into it thanks.
What has me stumped is nothing has changed other than getting a new unit. Different brand but all the same measurements and values my 13 yr old unit had. Never had an issue with condensation or high humidity.
Right now indoor temp is 72. Humidity is 65%

 

[bigb56]

Can it be possible the new unit is cooling better thus shorter run times leading to less humidity being removed?

 

[Fitter30]

Need a probe style thermometer not a ir. After unit runs for at least 20 minutes need to take temps at filter rack and 18-24 " from the evaporator. Will have to drill a hole in the duct for a temp reading. Want to know the temp difference. The duct in the closet and bath are probably not sealed and hot air is entering from attic. Have you look up at grill and its dirty and ceiling around it ? That's not from the air blowing out but dirt in the air getting picked up by terbulence from the air air the grill picking up the warm air around it and sweating.

The difference between supply and return temps has a lot to do RH.

 

[arod0422]

that is what the guy who installed the new unit is telling me. Says an option is to reduce the fan speed so the house takes longer to reach the temp

 

[Fitter30]

that is what the guy who installed the new unit is telling me. Says an option is to reduce the fan speed so the house takes longer to reach the temp

When RH is high the house when first walking in might feel cool after a few minutes you feel that it might not be so cool calmly. System can run from 18-24° different. Design is usually 20°. The bigger the difference the slower the air is crossing the coil the more RH it's picking up. Above 24° the coil can freeze over thats bad. Normally wouldn't go over 22°.

 

[arod0422]

so slowing the fan is a viable option?

 

[Fitter30]

When RH is high the house when first walking in might feel cool after a few minutes you feel that it might not be so cool calmly. System can run from 18-24° different. Design is usually 20°. The bigger the difference the slower the air is crossing the coil the more RH it's picking up. Above 24° the coil can freeze over thats bad. Normally wouldn't go over 22°.

Yes that is why in post 4 ask for temp readings and post 6 blower door test to see how tight your house is. Windows,doors and seals add up in a hurry. 1/8" crack 36" long is 4.5 sq inches

 

[Slomoola]

Also the old blower wheel was probably NEVER cleaned and packed full of dirt. Causing less air flow through the house. Running longer pulling more humidity out.

Old refrigerant charge was probably not perfect on the old unit. Many a factor that could cause this. Clogged air filters or people using those MERV 18 poison gas lab filters killing air flow. Use MERV 4 filters or less people.

People closing the register vents off throughout the house. Old people are notorious about this. Closing vents thinking they are saving money......... Unit is NOT designed to run with vents shut off.

 

[Slomoola]

In humid areas, wise to say install a 4 ton to help pull moisture out.

 

[RetiredInGueydan]

Hello All,

I had a new AC unit ( 5 ton) put in a couple months ago (inside and outside unit).
About a month in i started noticing condensation from 2 small vents one in a bathroom and one in a closet. None of the other vents trough out the house have this issue. The humidity in the house is consistently over 65%. Was never over 60 with the 12 yr old unit.

I've gone in the attic and made sure the lines coming to these vents were properly insulated and had no tears or leaks.
The unit itself looks to be sealed perfectly. and the house cools nicely.

Not sure what could be the problem here. and why its only in these two place

Any ideas

The lack of proper return air flow in small areas and inadequate attic ventilation can lead to this condensation problem.

 

[Slomoola]

The lack of proper return air flow in small areas and inadequate attic ventilation can lead to this condensation problem.

Many a factor for sure. Most houses the return is too small.

 

[arod0422]

Update:

Went back in the attic and resealed all the vent housings. No more condensation in the closet.

Also noticed that the exhaust fan in the one bathroom with the most condensation, had no sealing whatsoever and the metal duct hose was held together with black duct tape. Fixed that.

Still getting a tiny bit of condensation in that bathroom but only after hot showers. (was constant before) so thats an improvement.

Overall humidity in the house has dropped but still can't get under 51%. temps here have really dropped off so I'm assuming that has helped as well.

 

[Fitter30]

All resisters with air blowing out creates turbulence. The turbulence drags some room air across the louvers and they sweat. Walk into a office building they have ceiling diffusers and you will see dirt on the ceiling. That dirt isn't coming from the air blowing out it's from turbulence picking up dirt in the air. Bath rooms most people don't run the exhaust fan long enough. Wall timer running fan during and after 20+ minutes. Also works for odors.