the joists run north-south and there are two lvl beams running east-west which the joists attach to with joist hangers. If you put the unit on the second floor you can't get to the other sides of the lvl beams. I guess you could if you dropped soffits but it wouldn't look good on the first floor. if the unit is in the basement we could make three supply/return runs up from the basement to the second floor, one on north side of the north lvl beam, one in-between the lvl beams and one on the south side of the south beam, using open web trusses you could then run the ducts as needed for each room, Guess maybe there is another way but I haven't found one without major changes to the layout. In my area nearly all the homes put the second unit on the second floor and run the ducts in the attic. This post was edited by wynnejt on Wed, Nov 12, 14 at 20:33

OK, after doing some more research I think I may have answered my own question! Would like some confirmation from the experts here though. Read that each ton is about 400cfm and that a 16in flex duct is only rated for 850cfm. So that would make the third companies solution a bad idea! Please tell me if I am understanding this right? Also, I am looking at buying a Goodman two stage 16 SEER 3 ton unit. The model numbers are: Condenser Model No. DSZC160361 Air Handler Model No. AVPTC313714 I have read opinions of Goodman and I would buy a different brand but at this point money is a big factor. Anyway, is it worth it to get the Comfortnet thermostat or would a White Rodgers model # 1f95-1291 work just as well? Also, is there a performance benefit to the remote outdoor sensor or is it just to display the outdoor temp? Thanks for all the help!

Tigerdunes brought up demand defrost versus timed defrost. For the past 18 years, I have dealt with my Lennox defrost scheme. The only times I heard it go into defrost mode were when the unit was first running in heat mode. The unit would switch over from heat to defrost, the defrost cycle would complete and everything would turn off. I never heard it run a defrost cycle when it was not first heating. I rarely heard it go into defrost. I never heard it defrost on a fixed cycle such as every 90 minutes. Am I to understand that a Carrier will just go into defrost mode every X minutes whether it needs it or not and is not in a heating cycle; just turn on and defrost itself? I found this information in the Carrier 25HNB6 heat pump installation instructions: AUTO defrost adjusts the defrost interval time based on the last defrost time as follows: When defrost time When defrost time 3-5 minutes, the next defrost interval=90 minutes. When defrost time 5-7 minutes, the next defrost interval=60 minutes. When defrost time >7 minutes, the next defrost interval=30 minutes. The control board accumulates compressor run time. As the accumulated run time approaches the selected defrost interval time, the control board monitors the coil temperature sensor for a defrost demand. If a defrost demand exists, a defrost cycle will be initiated at the end of the selected time interval. A defrost demand exists when the coil temperature is at or below 32_F (0_C) for 4 minutes during the interval. From that description, if the time interval elapses and the coil is not at 32 degress, then no defrost will take place. That, to me, sounds like a form of demand defrost. Is Baldloonie saying that the coil could be at 32 degrees or less without frost and, therefore, a defrost cycle would be unnecessary? What kind of ambient sensor detects presence or absence of frost? Neohioheatpump asked, "When your old A/C would run, was it producing water?" It was producing water and I saw it dripping from the condensate drain. One weekend I went out of town and came back to find water on the floor around the return box that the fan coil sits on. I opened up the access and found the interior insulation of that box soaked. Turns out the condensate line was plugged. Took awhile for that to dry out. On the other hand, this past summer I did not see water dripping from the condensate drain. The drain line was not plugged and the drip pan seemed dry. I thought it was because I had dried out the air so much with the two dehumidifiers that there wasn't enough remaining for the A/C to remove. Cooling was normal. Running the fan on manual started with the installation of the Lennox and an associated Honeywell Electronic Air Cleaner. The house suddenly became dusty and I blamed the EAC for not doing its job. The Honeywell zone representative came to my house, sized up the situation, and told me to run the fan on manual so that the dust would remain suspended in the air and available to be captured by the EAC. I did that and it was of no help for the dust situation but it did help reduce the temperature differential between the first and second floors during cooling so I kept doing it as a matter of routine. Thus, I cannot say that not running the fan reduced the humidity. Though I complained about humidity, the heat pump contractor never told me that I was humidifying the house by running the fan (on orders from the Honeywell rep). I will continue to run at least one dehumidifier in the completely below grade basement during the summer because I want that area to be warm and dry to avoid mold and mildew. I've been in the basements of other houses in the area that don't use dehumidifiers and they stink. Mike Home said, "You stated in an earlier post that you run the fan in the summer because the upper floor is 2-3 degrees hotter than the lower floor. I think adding the attic insulation will help this." I agree that adding attic insulation could help. But, having a Dutch Colonial house with a barn-like roof that is covered in dark shingles on the east and west sides causes a lot of heat gain through the second floor walls. I'm not keen on opening the walls to determine the amount of insulation or add to it. Changing to a light-colored roof would make the house look out of character with the neighborhood. There are newer shingles that reject heat gain that I will investigate. Mike Home also said, "You could also zone the first and second floors, but this is expensive and probably not feasible with your current duct work." There is but one main feed duct and it runs through the basement. There is no way to segregate the room feeds in this scheme without doing each one individually. I'll leave that expense to the next owner.

It really depends on the situation and every home and need are different. In the basement overcooling situation, you gotta do it for the comfort. Some people have insulation between the basement and living space so you don't want to lose your heating to that area. Then there is the problem with imbalanced pressures. If there are supply duct openings, where is the air going to go? If the basement is closely coupled to the area with a return (upstairs?) and you don't mind a little air down there to dehumidify, or warm it up a little bit, leave it alone. If the basement is sealed off from the return upstairs, it may leave the area more closely coupled to the outdoors. It will be pressurized and the air will tend to leak out through the openings and cracks to nature. That will, in turn, depressurize the living space and suck unconditioned air from random cracks and openings up there. It might even come down some flues. If that is going on, you gotta fix it. You can do it by adding a return or sealing the supplies. Ducting systems are complicated. I hate them.