Newly installed furnace does not provide enough heat
I recently had a contractor install a 3 ton Bryrant 925T (two stage variable speed 95 AFUE ) furnace to replace my original 5 ton carrier 80% efficient furnace for my first floor which is almost 1900 sqft (I have another 5 ton system for my 2nd floor which is more than 1900 sqft.). I double checked with the contractor about the size and the contractor said my old system was oversized which I believe so.
However, the new system does not provide enough air flow. I can only feel air flow within 1 or 2 feet from the vents (I have 10 vents on the first floor). It takes more than one hour to heat the 1st floor. I think I have at least 20% leak in the 1st floor ducts. I cannot do anything about the ducts because they are enclosed between floors.
My contractor told me that the high efficient system takes longer to heat the house, but it seems too long for me. Also the air flow is so weak that heat only accumulate around the vents.
Is what I described normal for a 2 stage variable speed high efficient system or I need a system with bigger size?
Thank you in advance.