Static Pressure Problem?

[jdm2447]

The return trunk is already 8x20 (new) and the return drop is 14x20(new) how much larger do they have to be?A additional 8x26 floor return was added to living room at bottom of staircase,to add additional path for return air from upstairs.All the additional returns are on outside walls and supplies are located in center of house.From what i've been told it is opposite from what is recommened for today standards.The one who did the new duct work for me is a tin knocker with 30+ years experience mostly with commericial buildings.He does not work on ac or furnaces,works on just fabricating the sheetmetal parts and installing them,he does not have anything to measure static and I dON'T know that he would be able to if he had the right equipment.

[dash]

What is the size and model numbers of the equipment?

You will need to find someone to test the supply and return static,the supply could be really high and the return low,so the supply would need to be remediated to lower the static.

As far as the returns ,depending on the equipment size,you could add turning vanes ,at all 90° turns.Looks like two in each direction at the top of the return drop,plus one going into the filter.This will lower it some,can't tell from here if that enough.

Same for the supply side 90° turns if there are any.

[jdm2447]

model # 355aav042080,cnpvp3621acaaaaa,2.5 ton condensor 165a. Thanks for your help.