I was thinking that the cool air (AC'd) was leaking out the duct's seams and joints and causing the condensation.What you need to do is insulate them to stop the condensation in Summer and heat loss in Winter. The best way to seal them is with mastic.
Not a real common problem in our area but I have seen it happen. Once the insulation is wet it is really of little value. It will dry and become nearly as effective as before being wet but the original problem will reoccur given the right conditions.Mine are under my raised house, they also sweat, and are insulated. Not sure if there is a way to stop it or not.
In a properly designed system closing ducts will not cause the coil to ice up nor will the air become appreciably colder. The system will sense the reduced need for cooling and shut the compressor off while allowing the evaporator fan to run. When the system again calls for cooling, it's controlled by compressor head pressure and/or suction pressures, the compressor will again cycle.You may need to balance the air handler to increase the volume of air. The lower the volume, the colder the air and the greater the propensity for condensation. Some people close off too many registers, trying to limit how large a space they cool but the air then is colder because less of it is moving across the coil. Reduce the flow too much and the coil will ice up.
Sounds like newer technology. Maybe the systems I've had to deal with are older than you. Some of my systems don't even have the low ambient air option and have issues cooling when it's colder outside than inside.Just what I've seen doing this kind of work for a few years.
It sounds like the best thing will be to wait till late winter when all the existing insulation is dry from the heating season and then fix/add insulation (seal any joints that are leaking badly).I would not so much worry about sealing them .. more so insulating them REAL well.
I'm surely no HVAC guy but have been around commercial construction for many years. And have seen duct work sweat in un conditioned spaces, only to be cured with Duct insulation
Older than me would be ancient.:trink40: I cut my teeth on the old ammonia systems and open wheel compressors. Even worked on one that had a hit & miss engine for power. It had replaced the old steam engine that was the original power source.Sounds like newer technology. Maybe the systems I've had to deal with are older than you. Some of my systems don't even have the low ambient air option and have issues cooling when it's colder outside than inside.
Great plan! Insulating the ducts will take care of your moisture problem.I see lots of sweating ducts both from tore up insulation as well as systems never insulated when originally installed.It sounds like the best thing will be to wait till late winter when all the existing insulation is dry from the heating season and then fix/add insulation (seal any joints that are leaking badly).