Ductless AC, A Guide To Mini-Split Air Conditioners
Ductless AC systems were developed in Japan where a space saving and energy
efficient option was required for heating and cooling the home. Since that time, the technology has
matured enough to make them an attractive option elsewhere.
These systems, sometimes referred to as mini-splits, can replace the traditional central ducted system and
work in much the same way as the traditional air conditioner or heat pump. They have advantages such as
they do not take up any floor space for a fan coil or furnace. The fan motor is smaller and therefore
produces less noise. Finally, there are no air ducts so the system is typically half the cost to install.
A condensing unit is located outside the home. This part of the system contains the compressor which
circulates the refrigerant to produce the cooling effect. There are several types of compressors but the
latest innovation is inverter technology. This technology allows the compressor to operate at an almost
unlimited number of speeds. These units normally start at full speed when there is the need for heating or
After the setpoint is reached, the units typically reduce the compressor speed to pump just enough
refrigerant to match the requirements of the home. This provides energy savings as well as longer cycles.
The longer operating cycles provide more cleaning/filtering of the homes' air and more even temperature
distribution. A fan coil can be mounted on the wall or ceiling of the room to be conditioned. Other units,
called console units, have a free-standing fan coil unit that sits on the floor. The fan coil unit
contains the evaporator coil, fan, and filtering system along with the control components.
Some units include advanced filtering systems such as carbon activated filters, electrostatic filters, or
anti-bacterial filters. Many units include more than one filter technology. Some units also include a very
small motor to move louvers back and forth. This is normally called swing mode and enhances air
circulation throughout the room. The most advanced units move the louvers both up and down as well as back
The ductless ac system is usually controlled through a remote. Here you set the temperature, change the
modes of operation, and set timers and other advanced functions. The most advanced units include a
temperature sensor in the remote. This is commonly called "I FEEL" and is beneficial because the system
senses the room temperature at the remote and not high on the wall. This allows for better comfort. Other
units have optional wall mounted controllers.
Many of the units include advanced modes of operation. One of these is called the turbo mode or quick cool
mode. This mode runs the fan and compressor on highest speeds to provide the most cooling in the shortest
amount of time. Most units also have a dehumidify or dry mode. In this mode, the fan is operated at lower
speeds to increase the amount of moisture removed from the air. Some units have a sleep mode where the
setpoint is raised or lowered by a set number of degrees on a scheduled basis at night. This allows for
energy savings without noticeable changes in comfort level. (Once you are asleep, you are less likely to
notice a gradual temperature change.)
Some units include a fresh air option. This allows a small duct to be connected and to bring in air from
Some ductless ac condensing units can be connected to more than one indoor fan coil unit. These units are
called multi-split units and can help you to save a lot of money when more than one unit is required for