I had a Carrier Infinity system installed a couple months ago (58MVP060-14 and 38TDB037), and ever since, I've had duct sweating problems that I never had before. I posted on this before, but now have more information and possible solutions
I live in a two-story house with finished basement, and there is no door between the basement and first floor. The temperature in the house is 75 with 48% humidity, but the basement is at 65 with 63% humidity. This is actually the same dew point (53F-54F), though, so the basement isn't damp but just cold.
The uninsulated supply ducts in the basement are sweating like crazy. I've got puddles of water and some rotten wallboard where a duct goes between the basement ceiling and the floor.
The duct sweating never happened before with the old system. I figure the new system is either removing more heat (and hence the supply air is colder), or the airflow is less and therefore a greater temperature drop, leading to cold ducts and condensation.
I think I've isolated the problem. Even with the Infinity Control set for AC airflow to Maximum rather than Efficiency or Comfort, the airflow never goes to 1200 CFM but stays at 1050 on my 3 ton unit. I assume my old single-stage unit was at 1200. If I could get it to 1200, it may be enough to stop the sweating. Does the Infinity Control always override the switches on the furnace control board? Or could those be set wrong? The installer says they're set correctly, but I still never get to 1200.
I'm planning on insulating as much of the ductwork as is accessible even though I didn't think it was typical to insulate ducts in conditioned space, and I've got the supplies in the basement closed to try to keep the temperature up down there. (There is a return in the basement that is open.) Any other suggestions? How can I force the airflow to 1200? Is it normal for a basement to be this cold without any supplies open?
Thanks for your help. The installer doesn't have any suggestions.
[Edited by kcb203 on 07-26-2005 at 09:15 PM]