One more thing to add, In the winter there is actually ice on the duct in between the insulation and the duct. Maybe the insulation failed?
To better understand you, please clarify.
1. Where
exactly is the ice located? Example: coupling at interior duct to outside termination.
2. Is the interior duct metal with installer added insulation or an insulated flex-duct?
3. Is the exterior termination completely foamed around? Example: coupling and neck.
Maybe the insulation failed?
That may very well be the case, in a sense. If it is flex-duct, you may have a hole some where in the outer wrap or the wrap is not completely sealed at each end. Both ends of the duct should be foamed. Otherwise, condensation can occur between the insulation and the inner duct or at the coupling interface.
If it is metal duct, insulated or not, replace it with high R-value flex-duct.
What is the dew point of the basement environment? Basically, the basement environment is coming in to contact with un-insulated fresh air components and causing condensation.
Since the damper is exterior, there may be negative pressure in the interior duct at times; pulling the basement environment in at the coupling. It is important the termination be completely foamed around, to seal. Always use a closed cell foam on exterior components.
Pressurize Only is a trick used in southern climates while you should be either doing a balanced or exhaust only
With proper design practice, "pressurize only" is fine for any climate. I agree it's not as efficient as a balanced design though.
If you're blowing condensate off of the coil back into the ductwork, my guess is your fan speed is too high.
I believe SLSTech was referring to re-evaporation of the coil's condensate. It can take up to 20 minutes for a coil to drain.
Slow that puppy down. Besides, at a slower fan speed, you'll have a colder coil and get even better dehumidification.
That's an excellent on-demand stage, for humid regions. However most technicians do not properly design this stage. They risk compressor damage, over time. Since efficiency plummets, a timed lockout is required after this stage. Otherwise, this stage is highly in-efficient if moisture is allowed to be re-introduced.
That's where a good HVAC technician is worth their weight in gold. They don't just take the default fan speed settings out of the box and assume their right. They actually take the time to check temperatures and make sure they get that coil as cold as possible without icing it completely.
:thumbsup:
As professional technician, I would never design like this, especially a single stage condensing unit. Taking a coil to near icing will raise head pressure and possibly flood the compressor, TXV or not. With multi-stage condensing units, it is easier. However, a blower lockout is still required, after this stage.:nerd: