It can work well in a basement, but a few things really matter.
First, insulation and damp control. Basements can lose heat through walls and floors, and if there is moisture, performance and comfort will suffer. Make sure waterproofing and insulation are sorted before installing.
Second...
Yes, R290 does expand.
R290 is propane, and like all refrigerants it expands when it changes from liquid to gas inside the system. That phase change is what allows it to absorb heat and move it from one place to another in an air conditioning or heat pump system.
It also expands as...