We have a 2100 sq ft 2 story house built in 1970 with 4 bedrooms upstairs. The bedrooms are much cooler than the main floor, so looking at adjusting some of the dampers in the basement. Just not sure which ducts are typically serving the 2nd story. In the basement, I have the main duct with round supply ducts branching from the main. The main ducts have the levers available to adjust the dampers, while the supply ducts have small wingnuts. Do the round supply ducts typically supply heat to the 1st and 2nd floors, or simply the 1st floor? Our basement is mostly finished, so unsure if I'll be able to access everything I need to. I have attempted opening/closing registers to no avail.
Been trying to find a good diagram of typical HVAC system in a 2 story house, but have been unsuccessful.