I know this has been asked and discusses Ad nauseum, but, I have a 2100 sqft ranch style home in north Texas. I should also point out that I have a terrible east / west exposure. The west side of my house is the entry way with huge windows all the way across. The house came with a 4ton York contractor grade crap AC that never was able to get the mid summer temp in the house below 82 degrees.

We started by having all the windows in the house tinted, which made a huge difference. We then added an additional 9 inches of insulation in the attic. I also improved the ventilation in my attic space as well. At about 7 years we decided, after the compressor locked up to get a new AC unit. My big mistake was not replacing the furnace and all at that time. We got a new Carrier (38TXA048-321) and an new evaporator coil as well (CE3AXA048).

This unit seemed much more capable of handling the summer heat. With this set up I was a least able to get to and hold my set point for most of the day. Currently I set the thermostat at 76 Hold and it will hold it until about 3pm at which point the temp begins to rise steadily in the house until about 7pm where it peaks at about 79.

The system was fine for the first 3 seasons and then every year since that it has had some kind of MAJOR malfunction. Last year the compressor locked up and had to be replaced along with the cap. Yesterday.....the same thing happened except this time the fan motor went with it. Again, this unit was installed new in 2001 and is now on it's 3rd compressor. I should add that I have always maintained my units in good working order, that is to say I always change out my filters every month and have a season checkup for both furnace and AC every year. I also keep all the grass and dust washed out of my condensor unit grill.

My first question, and forgive me for asking, do you think I need more capacity? Is 5tons what I really need considering my high ceilings throughout the house and crappy east/ west exposure? It just seems to me that 4tons has never been enough for this house. I know that slightly under size is better then over but, if I set the therm to 76 is it too much to ask that the unit keep the temp at 76 all day?

Second question, is Carrier junk or did I just get a lemon? Again this is a 7 yr old unit that has broken down every year for the past 4 years. While all this work has been done under warranty it's still a major pain in the rear to have to sit in a sweltering house while the techs chase down new compressors and fan motors to replace the year old ones.

Thanks in advance for any constructive advice you can offer.