Last November, I upgraded my HVAC to a Trane XL19i. I was satisfied with it all winter long but am having a slight problem this summer that I would like some advice on.
I live in Dallas, and the unit is in the attic. Supply ducts, except one, are in the crawlspace with ducted returns in the attic. All ducts are steel, wrapped with 40 year old duct wrap. With the old unit, the supply in the attic was typically the most forceful and the coldest (as it is the shortest run from the unit - approx 30'). However, with the new Trane, this vent is the hottest vent in the house, typically delivering AC at temperatures warmer than the ambient room temperature.
The installing contractor reviewed this problem, took measurments and found that after the system was 'up to speed' there was a 20 degree drop at all the other vents and only a 2 degree difference at this one vent - after 10 minutes of dumping 100 degree air. Their suggestion is to add 3" of insulation to this duct (two 1.5" layers) and hope this corrects the problem. Since I did not have problems with heat gain in this duct with the previous HVAC system, I am concerned with the success of this approach. I also have concerns over triple wrapping a duct and condensation.