Here's a question:
I have a 5 ton air handler with an opening in the top of it obviously.
That 5 ton unit was obviously designed so the opening can actually push 5 tons of a/c through it.
If my supply plenum is the same size as this opening then it should be adequate I would think since the hole in the air handler is all the air handler can put out anyhow.
BUT, I had a guy come out with a ductulator and measure the supply plenum and said it was too small for a 5 ton unit ! How can this be? It is the same size as the opening in the top of the unit.