a closed-loop refrigerant system that uses water lines to the indoor coil/air handler
Sounds like an air to water monoblock heat pump. Common in Europe. But you can only get the water up to about 50C efficiently. Not as good as refrigerant. So you need a large radiator to get the heat out into the room. Using wet underfloor heating as a giant emmitter works well. But otherwise it makes them tricky.
Some people are trying for minisplits with propane in the lines which is not a greenhouse gas so they hope anyone will be able to install it without a licence.
Sounds like an air to water monoblock heat pump. Common in Europe. But you can only get the water up to about 50C efficiently. Not as good as refrigerant. So you need a large radiator to get the heat out into the room. Using wet underfloor heating as a giant emmitter works well. But otherwise it makes them tricky.
Some people are trying for minisplits with propane in the lines which is not a greenhouse gas so they hope anyone will be able to install it without a licence.