I have a 3.5T AC. If I had a 4T AC, what critical parts would be different?
The reason I ask ...
I bought a new 2300 sq. ft. standard stick home from a national builder about 10 years ago (in the Pacific NW). The AC was added at the time, and it has never worked well (having moved here from the SW, we were surprised at how small the AC was). It used to hold about 10 degrees below the outside. The builder has had AC folks come out and work on it every year, and they have gone over the whole house - moved ducting around, changed the vents, etc. etc. Last year, things got a little better, but it still doesn't hold much more than 15 degrees below outside - and it can't ever cool the house. If we turn it on during the day, we have to wait until the house cools naturally overnight and then see if it can hold it the next day.
So - this year, the builder has brought out a new AC group. They are going to be replacing the fan blades in the outside unit. They are hoping to increase air flow for the system this way.
I have always suspected that a larger unit is required. So - I was wondering what actually changes if we moved to a larger unit. I assume it is more than the fan blades :-)