I've recently completed a bedroom addition, but have not run extensions from the existing ductwork for A/C. I could run a new air return and additional vents. But does anyone know of a floor mounted, 120 volt product that would work in place of expanding the system?

Also, I'm not convinced our A/C unit is sized correctly. Our home is about 4,000 square feet, 1 1/2 story, finished basement, but I have no way of telling if the unit is large enough. Can you tell from the model/serial plate? What size unit is typical for a home this size?

It shoild not be much of a problem taking 2 or 3 6" runs off the existing trunk line for the new room. As for your house, 4000sq' ...? You would need about 8 tons of A/C to cool the entire house. That's if you have 8' ceilings. The model # on the condenser shoulkd give you a # like 024/036/048/060 etc. Tonnage are in increments if 12. 12000 BTU/Hr is 1 ton of Cooling.
Big House, I hope you have at least 2 Air Conditioners.........