My air handler's plenum has 3 flex ducts connected to it: 16" main supply to 3 rooms + hallways, 10" duct to a room at other side of the house, and 8" duct to utility rooms.
I disconnected the 10" and 8" ducts to check the air flow and noticed that the air coming out of the 10" is warmer than the air coming out of the 8" and the 16" ducts. The temperature differential is about 4 to 6F.
What would cause this to happen? I would thought with the air velocity and pressure inside the plenum, the temperature of the air should be uniform when going into the ducts.