New HVAC - weak ac upstairs
Hi folks - here's my deal - replaced hvac with 3 ton trane system for 1800 sq ft 2 story home in NJ. New windows, air sealing and roof. Ac on ground floor works nicely now with new equipment and two stage thermostat. There was no c or heat in front room so they ran ac from back bedroom. The air seems very weak upstairs and the register in the front room is barely blowing anything. I am very disappointed after laying out 15k that I got 7 degrees + upstairs above downstairs and 5 degrees + above the back bedroom. Insulation is perfect!! Cheated, measured etc. HVAC co is telling me this is normal or maybe they now got to increase duct size because it's a down draft (?) system and they need to cut off air downstairs to feed upstairs. Just feel I am being not treated fairly here. Asked for a price on new equipment for upstairs and downstairs and three visits later I am being told adjusting dampers or installing a 'scoop' will not cure this. I have paid 10k$ but am afraid if I pay the other 5$k I will never see resolution. Am I being unreasonable and what is a fair approach? Any and all answers greatly appreciated.