I have a York rooftop package unit, model D5CG060N08206D, which I believe is 5 tons from the "060" in the model.
Rule of thumb says I should have 5tons x 400cfm/ton = 2000cfm of airflow.
The supply and return plenums drop down into the attic about 18". Outside plenum dimensions are about 16x10.
The are two flex return runs, both 14". Hallway return is close to the unit, but does a 270 to get to the plenum. The other return is on the opposite side of the house, about a 50' run. Returns are 20x20.
There are two flex supply runs, 12" and 14". The 12" feeds the near side of the house and wye's/reduces about 3 times in the first 10 feet. The 14" feeds the far side of the house, again about a 50' run, before it starts wye'ing.
Looking at a ductulator, in order to move 2000cfm at 700fpm, I should have the equivalent of two 16" supply ducts and two 16" return ducts.
What you think?
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