seeing house plans is the only way to determine if ducts can be located in a conditioned space. you could fur down a common area to supply to all rooms if layout allows and put ahu in closet on second floor.. if layour allows. make it clear to hvac company that this is what you want and work with them. usually closets are approx 3' by 3'. I like solid doors that seal well to platform and retruns that are air sealed with fbg in door. filter either at door or under ahu. are you sure you need 4 tons on 2000 sq ft? maybe a single unit with zoned dampers would serve you better than multiple units. sounds like 500 sq ft rule of thumb sizing. you need a load calc and a duct design to determine size and properly lay out and size ducts. best of luck.

thanks Bob. this is a "downflow" installation in a supply plenum directly in floor crawlspace below. I agree best would be to move the air handler out of the room. I open the access panes to take a look. I now don't know about moving the coil out without stressing the copper. I guess I have several options and would appreciate your ideas. Do you think an hvac company would remove refrigerant and condenser coil (I guess that is half the weight), seal both sides, and put back the coil and refrigerant in ten days or so? How much would such a job for both removal and reinstall coil and fluid cost ballpark in an urban area (DC)? I could throw in paying them to clean the five year old condenser as well. Would it be the same as asking them just to move the whole unit outside the room for ten days? I might want to rebuild supply plenum, replace floor drip pan (it is 30% bigger than needed)). I might ask them to do this as well. Ages: roof unit compressor, 2 years air handler housing, electronics, squirrel fan all 14 years condesnor coil, five years floor (galvanized sheet metal) drip pan, plenum, ducts, 25? years I have a place to keep the air handler and coil (master bedroom about 10 feet away) for 10 days (estimated time until my wife says the air handler or I have to go.) This is a four story town house. I have the top two floors with my utility room on the top floor and three finished floors below. So I am really interested in putting a sturdy floor, and while keeping my individual drip pans and pvc to the floor drain, doing my best to isolate the room so anything really bad goes down that floor drain. If dealing with the air handler is too much I can work around it but I hate to do a job halfway.

Thank you guys for the input. Unfortunately moving the alarm box a couple of feet is going to cost me. It has about 25 wires coming out of it . ADT will charge me $113 for 1st half hour and $22 for each additional 15min. God knows how many hours will take to figure out the spaghetti of wires. Considering that I had the old unit in the attic for 14 years with no problems and the contractors were 50/50 on relocating the unit, I am leaning more toward keeping the unit up in the attic. I feel sorry for anyone who has to install these units in the attics of Florida.If anyone is in to sitting in hot sauna, you can use my attic free of charge.

Is the attic vented or sealed? Where is the return air entering?