There are two possible ways to solve this problem.
Why do ducts in attic collect water.
Moisture can be a sign of low duct temperature.
So water is condensing on your ac ducts.
When water condenses and drips into your attic or home it can cause a some serious secondary problems.
Persistent ductwork sweating may eventually lead to water damage.
In more cases than not a 3 ton ac with the ducts in the attic has a ton or so of load that s just from the location of the ducts in the attic and the associated duct gains leakage etc.
Martin holladay editor of green building advisor responds.
First water dripping off of your ducts and onto your insulation can cause the insulation to compress which decreases it s r value or ability to insulate.
The first is to keep your ducts warm.
Slow water leaks might not be noticeable right away but over time they create an ideal breeding ground for mold in air ducts and also water damage in your space.
The last usual cause for condensation on a duct system is if the ducts are not properly hung or they are touching each other.
The remaining 2 tons of capacity is at least 1 5x oversized for the actual 1 load.
The most likely explanation for the water in your ducts is that warm interior air is entering the ducts during the winter and the moisture in the air is condensing on the interior of the cold ductwork.
Occasional condensation on a c ducts is not a problem but keeping an eye on the situation is recommended.
The condensate drain system collects water removed from the air during the cooling process and disposes of it into a drain.
When ductwork is touching it forms a very cold spot where they are touching thus condensation begins.
A dehumidifier can help keep the air dry enough to prevent mold.
Moisture can also collect in the summer if cool air passes through a duct in a room that isn t air conditioned.
Installing ducts in a vented unconditioned attic is always a bad idea.
Why is this a problem.
Ducts are located within an unvented crawl space.
Excessive condensation can also create conditions favorable to mold or mildew forming in areas surrounding the duct itself.
Ductwork located in an attic must be hung properly so that the insulation can do its job.
And that water can then travel to the ducts or vents.
If your air conditioning system is installed in the attic or on an upper floor problems with the condensate drain could cause a water overflow from the drip tray.
During the heating season unused air conditioning ducts located in unheated rooms can collect moisture.
Jump ducts which do not directly deliver conditioned air from the hvac unit may be located in attics if all joints including boot to drywall are fully air sealed with mastic or foam and the jump duct is fully buried under the attic insulation.
There are a few common reasons for water in air ducts.
Ducts belong inside your home s conditioned space.
Use a dehumidifier in a very humid environment such as an indoor pool room or basement space.