I recently removed a boiler/ radiant heat system from my 30+ yr old house and am installing a force air funace system. My present AC system (about 10 yrs old) is installed in the attic and eventually I would like to relocate and have a single central HVAC system. I have two questions that I am hoping to get answered, after reviewing about 15 pages of this forum and doing a search I could not find similar questions, great info though. 1st - I know that different manufacturers would like thier entire systems installed, but are there any major problems that may occur by having different A-coils installed with condenser units? In tlaking with a couple of professionals I am getting mixed messages. 2nd - I am also getting mixed messages on A-coil capacity. In pricing a few A-coils I was told by a Goodman distributor that I would need to upgrade the size of my A-coil to 4 tons if I wanted to go with a 14 SEER condensing unit. Calculations show that I need between 2.5 and 3 tons of capacity. I know that the flow rate valve would have to be changed, but does this increase sound right? Again I am getting mixed messages from a couple of professionals that I have talked with and I would like to get this installed initially instead of redoing it later. Thanks

Hi, I have a Carrier split unit (circa 1994) in North Texas that was running very strongly until about a week ago. Unit has a scroll compressor in condensor unit. Suddenly, I noticed that it was not keeping up with the heat load inside the house. -The air filter is of good quality, clean and new (<1 month old). -When I start it up with indoor temp at 82 degF and outdoor at ~90 degF, and let it run for 10-20 mins, the low-side pressure is 100 psig, while the high-side pressure is 200 psig. -High-side line at condensor unit is just barely warm, and low-side just barely cool (and no sweat). -A spot-check of the evaporator coil shows that it is just barely cool and is not sweating (and no water at all on floor of plenum under it). -The volume of air flow seems as high as it always has been, and there is no icing whatsoever on the evaporator coil. -There are no visible bubbles or excessive corrosion on the edges of the coil. -There is no, and never was, a filter-dryer on the high side line. One analysis I have been able to find for high suction-side pressure is "an obstruction in the line", as this design does not have an expansion valve (has capillary tubes). One tech wants to sell me a new evaporator coil, and another thinks that is not the problem. Any ideas from you all here? Thanks.