Central air conditioners and heat pumps are designed to cool the entire house. It employs the same types of components, materials, and systems as a refrigerator, including a refrigerant that changes from liquid to gas and back to liquid as it travels through a system of tubes and coils or fins that collect and give off heat.

There are two types of central air conditioners: a split system or a packaged unit.

In a split-system central air conditioner, an outdoor metal cabinet contains the condenser and compressor, and an indoor cabinet contains the evaporator. In many split-system air conditioners, this indoor cabinet also contains a furnace or an air handler. The air conditioner's evaporator coil is installed in the cabinet or main supply duct of this furnace or heat pump. If your home already has a furnace but no air conditioner, a split-system is the most economical central air conditioner to install.  

In a packaged central air conditioner, the evaporator, condenser, and compressor are all located in one cabinet, usually placed on a roof or a concrete slab next to the house's foundation. Air supply and return ducts come from indoors through the home's exterior wall or roof to connect with the packaged air conditioner, usually located outdoors. Packaged air conditioners often include electric heating coils or a natural gas furnace. This combination of air conditioner and central heater eliminates the need for a separate furnace indoors. 

Understanding the benefits of a central air-conditioning system

-Indoor comfort during warm weather – Central air conditioning helps keep your home cool and reduces humidity levels.

- As your central air-conditioning system draws air out of the rooms in your house through return air ducts, the air is pulled through an air filter, which removes airborne particles such as dust and lint. Sophisticated filters, like those found in the Lennox Healthy Climate® purification systems, may remove microscopic pollutants, as well. The filtered air is then routed to air supply ductwork that carries it back to the rooms.

Because the compressor-bearing unit is located outside the home, its operation's indoor noise level is much lower than that of a free-standing air- conditioning unit. 

Mini-split systems, popular in other countries, can be an attractive retrofit option for room additions and houses without ductwork, such as those using hydronic heat (see the heating section). Like conventional central air conditioners, mini-splits use an outside compressor/condenser and indoor air handling units. The difference is that each room or zone to be cooled has its own air handler. Each indoor unit is connected to the outdoor unit via a conduit carrying the power and refrigerant lines. Indoor units are typically mounted on the wall or ceiling. 

The major advantage of a ductless mini-split is its flexibility in cooling individual rooms or zones. By providing dedicated units to each space, it is easier to meet different rooms' varying comfort needs. 

The primary disadvantage of mini-splits is the higher cost. They cost more than a typical central air conditioner of the same size, where ductwork is already in place. But, when considering the cost and energy losses associated with installing new ductwork for a central air conditioner, buying a ductless mini-split may not be such a bad deal, especially considering the long-term energy savings.