Background: Our two-story house is about 3,000 square feet. When we bought it last year, it had two separate AC units, a 2.5 ton and a 4 ton. They were both old and died last month. We had them replaced with a single 5 ton unit, with two zones controlled by dampers (the original ductwork was merged into a single supply). The contractor insisted that 5 tons (versus the original 6.5) would be fine since the new system was much more efficient.
It was very hot today (pushing 90) and I noticed that regardless of what I had either thermostat set to, it just kept getting hotter and hotter. I felt cool air blowing out of the vents, but it simply wasn't cooling the house.
I got an emergency technician visit and he checked everything and asked me about the previous system. He came back inside and said, "We screwed up." It seems the 5 tons is not adequate for the heat load this house experiences. Although the system is working perfectly, it just can't cool both zones at once. As a temporary workaround, he suggested running just one zone at a time. The warranty manager is going to call me tomorrow.
I want to understand the options. I thought the technician said the 5 ton unit we have is the "largest residential unit available", so replacing it with something bigger might not be possible. What else could be done here? Could a second condenser be added? Is there some other way to beef up this system?
Hopefully the company will "make this right" as the technician said. But given that they apparently made a mistake on sizing it, I'm not confident they'll make the best recommendation.
Any ideas? Thanks!