The most common type of heating and air conditioning system in the U.S. is a “central split-system,” which has two parts: an outdoor condenser unit and an indoor air handler. The air handler is at a central location in the home and distributes conditioned air through ducts to registers (vents) in the floor or ceiling of each room.

    A “ductless mini-split” is also a split system with an outdoor and indoor unit, but there are no ducts. The conditioned air is distributed directly from the indoor unit, which is usually wall-mounted and controlled by a hand-held remote. Most mini-splits are heat pumps, but they are also available as only a cooling air conditioner.

    The wall-mount air handler can only service one room, but there are mini-split systems with an outdoor condenser that can serve up to four wall-mounted air handlers. The essential difference between the two types of systems is that a central system distributes air to each room through ducts, while a mini-split delivers refrigerant through small pipes to an air handler in each room it serves.

    Mini-splits are more popular in Europe, the Caribbean, South America and much of the rest of the world than in the United States. They have several advantages when compared with a central system:

1. Because they have no ducts, mini-splits avoid the energy loss inherent in a ducted system.
2. Each wall-mounted air handler can be separately adjusted, so a multiple air handler system creates individual zones that can be separately adjusted to the requirements of each room.
3. The small size makes them easier to install, and they are often the only choice when retro-fitting a system into a home with no attic or crawl space for duct installation—unless you are will willing to tolerate the noise and inefficiency of a wall/window air conditioner. 

    There are, of course, a couple of disadvantages:

1. A mini-split unit is about 30% more expensive than a central split-system.
2. Some people do not like the appearance of a wall-mounted air handler in a room.

    You can usually tell what type of system is inside the home by the shape of the outside condenser unit. Mini-splits have tall and narrow condensers compared to the cube shape of most central split-system condensers, as shown in the photo below.

    Mini-split condensers are also often bracket-mounted on the side of urban buildings in some areas.

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  To learn more about heating and air conditioning systems, see these other blog posts: 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• Does an old air conditioner use more electricity as it ages? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.