I had an energystar,leeds hvac designer run a manual J on my home. He came out with 1.5 ton unit for the upstairs and 2 ton unit for the downstairs. He stated once the basement was finished that would drop the unit down to around 1.5 tons as well.
My question during the negotiation process, We decided to upgrade the stock ac system to a Lennox XP16 2 stage heat pumps. and g61V furnaces. The HVAC guy said they would use a 2.5 ton upstairs and 2 ton downstairs. I since came to find out they do not make a 2.5 ton unit.
Now with the Calcs the manual J came out with 1.5 ton per floor. Can I get away with a 2 ton unit on each floor. I know its larger but its the smallest units they make.