I have a detatched game room that is 25' x 30' and it has a 12' tall ceiling that slopes down to 8'. It's a metal building with 3.5" of blown insulation in the walls and the ceiling has R19. The game room is one large open room. I'm locate in South Texas and it gets 104 to 108 Deg F here in the summer. I've been using a 25,000 BTU Window unit for 10 years now and it barely keeps up and I replace it on an average of every 4-5 years. During the summer it rarely cycles and is very loud. I just bought a new 3 ton split system heat pump which may be just a little large. (I figured a 2.5 ton would be fine but wanted extra in case I expand some). Here are my plans. On the 25' wall with the 8' ceiling, I'm going to build my air handler closet in the corner with the return vent on the bottom (25" x17"). I'm planned to use duct board to make a discharge duct 11"x 20" to go up 2 feet to the main duct. I planned to make the main duct from duct board as well and run it in a single 25" line at the ceiling. What size rectangle should I be shooting for for this main (only) duct and how many registers. I do want a decent velocity from the registers to "feel" it across the room. BTW, I'm doing all the carpentry work, wiring, and ducts and I will have a local guy come by and solder the line kit and commission the system. They don't have anyone available to come look and size the ducts until after the first of the year. Thanks Richard

is the air handler that doesnt shut off even when the t-stat is on the off position.any sugestions?