Ductless split system was probably the first type of air-conditioner. It's making come back in the U.S. and is widely used in countries like Japan. If you look at a window unit, you will notice in the front of the unit there is a cooling coil, a fan and control knobs. In the back there is another coil and a compressor. What connects the two ends are two hoses and an expansion valve. If you were to extend the two hoses to ten feet or more to separate the front end and back. You would have a ductless split system.
Most of the noise that comes from a window unit comes from the compressor. This system takes the compressor and puts it outside the home. The two hoses are connected to the compressor and the evaporator coil outside and the hoses goes into the home and attaches to the cooling coil. There are several advantages to the split ductless system. They are quiet, easy to install, can be installed on any wall or ceiling and can have up five zones. It used to be that these units were permanent, not any more.
These units install very easily and if you rent and move, all you have to do is disconnect the unit and pack up the parts. Afterwards, all you have to do is patch up a three inch diameter hole. Most ductless split systems are used primarily as cooling systems in the United States. They are usually manufactured as air to air heat pumps.
As a primary heat source heat pumps would not be recommended for areas where the winters are very cold. The reason for this is discussed in the geothermal/heat pump topic. Rarely would I recommend the ductless split heat pump as a primary heat source, however, there are instances that it would be. High rise apartments or condos that utilize several through the wall heat pumps. These units resemble an in the wall over-sized air conditioner.
The problem with these through the wall heat pumps is that they conduct heat easily because of their design. Ductless split heat pumps eliminate this conductive heat loss. It also gives more options on where the inside units are located. It does not necessarily have to be on an outside wall. Furthermore, you can have up to five units inside and only one unit outside. Most of these systems come with a remote control and can be programmed. This comes in very handy with smart house technology where you can control the heating and air conditioning remotely through the web or by phone. So if you in your car and you forgot to lower the thermostat, you could call your home and do it from there. The heat pump would be my last choice as a primary heat source.
Where the ductless split heat pump shines is when it is used as a supplement heating and cooling system. Let's say you have an addition put on your home and you extend your present heating and cooling system to it.
The addition becomes the center of activity in your home where everyone spends most of their time, which was the purpose for putting on the addition. Your energy bills increase because you are heating and cooling the entire home just for the addition. If the addition consisted of more than one room or a very large room, the ductless split system allows you to have more than one unit inside to better distribute the heating or cooling.
The way this system saves you money is by lowering the thermostat in the main part of the home and adjusting the thermostat for the heat pump in the addition. Most contractors would recommend a separate heating and cooling system for the addition. This is not a supplementary system, it is a primary heating and cooling system. A primary and cooling system cost a lot more to operate than a supplementary system does and in my opinion the supplementary system will do a better job.