I can’t really comment on your contractor’s behavior and the reasons behind convincing you on just a single HVAC system installation instead of two, simply because I wasn’t present at the conversation. I’d do 2 systems, as a contractor, because I could charge much more money for such installation. I’d definitely do it as a homeowner because it is much more efficient way to condition a multi-level property.
You options will also depend on the installed appliance features. For example, if it has a multi stage blower, special controller to use this feature, and there’s an air return port on the second floor, you can use the lowest speed setting to circulate the air constantly in order to equalize the temperature between all floors.
Please read the article and if you have more questions, provide me with as much information as possible about your home and HVAC installation, just click “comment” below.