Background on the building/section having problems with. It is a upstairs Commerical building that was converted from a old home to a church that helps people when familys have to stay in hosptial. Anyways the system that was there was a 2.5 ton upstairs and downstairs in which we replaced the upstairs system. This building has many room off to the sides on each floor that don't have duct drops just window units. So the upstairs is only about 1600 square feet.
The current duct system is as followed metal truck line ran about 60 foot every 15-20 foot they stepped it down. The system has (4) 6x12 retangle ducts that come off it that run less then 20 foot, (2) 9 inch drops that run 10 foot with two hard 90's, (1) 8 inch run that goes about 7 foot, and (1) 6 inch run that goes 5 foot. The first (3) 6 x 12 ducts are at the 1st take off, 2nd take off has (1) 6 x 12 drop ,(1) 9 inch drop, and (1) 6 inch, and the last take off has the (1) 8inch drop and (1) 9 inch drop.
My question is for the pros on metal duct work and who have experiance with metal duct work is how much cfm would this system handle? The attic has no insulation in it and on a day like today the current system will not get the upstairs below 85 degrees. They leave the Upstairs doors open to the downstairs part of the building and never run the window units unless someone is staying there. Also any idea anyone else might have i would sure thank you for your input.