Main Duct Resize

[misraels]

I want to know if it would be OK to cut my main hvac duct from 24" down to 16" rectangular or where i can go to figure that out. The run is 50' long and narrows down to 16" at about 20' and then down to 8" at the end.

The house is 3 years old and the main duct was sized to feed the main floor (ranch style) and full walkout basement. I am currently finishing the basement now, but with a new 8" square main duct on a zone control system. The main floor has 10 registers at floor level (1600 sq ft) and the basement will have another 9 registers at ceiling level (1450 sq ft).

Any help would be greatly appreciated as i could use the extra space in the ceiling for the new 8" run.

[Ed Imeduc]

I would not try and change this or put in a zone control on what you have there . You would also need a bypass damper in the set up . For just up and down in 1600sq ft .Just open and close the registers from heat to cool .

my .02 cents

ED ;)