I have been researching options on a new system, including duct work, for about 6 months. I have(so far) gotten 3 quotes. I didn't ask and no one offered a Manual J calc. All have said I need to go with the same size, 3 tons.
I have replaced old single pane aluminum sliders with double pane, low-e, single hung vinyl windows. I know the windows made at least some difference-the old ones produced a lot of condensate, interior in winter and exterior in summer. New windows have been dry.
The AC would run short times in summer, but kept it cool. I have learned that it is not necessarily a good thing to run short times due to humidty, but not being an HVAC guy I did not know this and figured I was doing well since the unit did not run a long time. Now I learn that long run times during the hot muggy season is good.
I figured when I ran the calc it would suggest a 2 or 2.5 ton unit. Well, the calc says 3 tons. And it is close enough that when I change my indoor design temp down 2 degrees(from 73 to 71) in summer it goes to 3.5 tons! I am going over my #s again, but don't think I missed anything. Any comments on this issue are appreciated. BTW, I am planning on a heat pump with VS air handler. And, if affordable, a 2 stage outdoor unit.