So it may be the addition of the returns which also makes it easier to get more air through the supply that did the most good and not the increase in size.
how did you know what it should be pushing? Did you do or have a load calc done?
BT, you are absolutely right, no doubt the additional returns were extremely helpful. But having said that, the additional ton made a world of difference on the extreme hot days here in houston.
What I meant by pushing was, if the Rheem Crit. was rated at 1600 for 4 tons, once we checked all of the discharge vents upstairs, we got darn near all of it. With the previous system we were way less on the the 3 ton. Even on our 100 plus days here, its been great! Unlike with the 3 ton that just ran and ran and never seemed to do anything.
Its one of those installs that I am sure the manual J would not support, but in this case I the customer am satisfied.
The home builders AC contractor would use a generic manual J on all like homes, not taking things like location, direction and or trees in consideration. You cant do that.
We have one side that is exposed to due west sun!