Central Air Conditioning is a popular term in the aircon world that can refer to a number of different things.  A central air conditioning system can refer to centralized heating and cooling unit, or a completely centralized air conditioning system.

When people mention central heating and cooling, they are often referring to the process of air going through a series of vents, ducts, plenums and outlets from a central air conditioning unit.  This is also known as ducted air conditioning.

However, central air conditioning actually refers to the source of the cooling; coming from a central point rather than locally near the point of air supply into a room or area.  A central air conditioning system serves multiple spaces from one central base location.  Cooling is generated at a central AC unit and distributed to air handling units (AHU’s) or fan coil units (FCU’s) located throughout a building.   Central cooling systems typically use chilled water as a cooling medium and extensive ductwork for air distribution.

Central heating, ventilation and air conditioning (HVAC) is the most popular way to condition air in large spaces, as it is efficient and effective.  Many high-rise office buildings, airports, shopping centers, schools, hotels, industrial warehouses, and many other large structures, use a central air conditioning system.  This is because putting individual air conditioner units in each room may not be required or the most cost-effective option.

What is Central Heating and Air Conditioning?

Usually when people mention central heating and air conditioning, they are referring to hot or cold air coming from a central unit.  This is also known as a ducted system.

This is a popular choice in homes needing multiple rooms to be conditioned from a central location.  It can work out cheaper than putting individual units in every room.  It also uses less space as there is usually just one outdoor unit outside, some outlets and a grille inside, a controller on the wall, and the rest is hidden in the roof!

Central heating and cooling is also common in small-medium size commercial buildings.  It can be a cost-effective option when large single-level areas require conditioned air but a larger industrial HVAC system would not be worth the initial investment in the long run.

Central Air Conditioning

Central air conditioning can often refer to conditioning the air inside a building from a central aircon unit. For a home air conditioner, the central indoor unit is usually in the ceiling or roof space of the home.  This unit is the evaporator portion of the refrigeration system and contains the cooling coil full of refrigerant.  When the indoor fan blows air over the evaporator coil, cold air is blow out into the room.

For commercial air conditioning, the central aircon unit is often found behind a suspended ceiling, in the space between the drop ceiling and structural ceiling or roof (plenum space), up on a mezzanine, or even built into a cupboard.  This is true for ducted air conditioners.

The condenser unit for both residential and commercial central air can then be found outside on the ground, raised onto brackets or up on the roof.  Heat rejection occurs at this condensing unit.

In the case of commercial packaged air conditioners, the evaporator and condenser are in the one unit.  A package unit is an all-in-one cooling system.  This unit is typically located on a roof, in the central plant space or in a protected area down on the ground.  Conditioned air then reaches rooms via a series of ducts.

Central Heating

Much like central cooling, central heating often refers to the provision of heat to the interior of a building from a central unit.  This could be in the form of a ducted reverse cycle air conditioning system or gas heater.

For a home central heating system, the central unit may again be the evaporator unit in the case of ducted air conditioning.  However, a heat pump drives heat generation and refrigerant is used for heat exchange.

Central heating can also come from furnaces and boilers.  Energy to produce central heat can come from electricity, natural gases, water/steam, wood/solid fuels, petroleum and other liquids.  Electricity and gas are the most common alternatives to a heat pump as they are the easiest to maintain.

Non-refrigeration central heating equipment is usually located in a furnace or boiler room, garage or basement.  Heat is usually blown into rooms through the ductwork (plenums, ducts and vents) using the forced air system.

Central Air

In a correct sense, a central air conditioning system refers to central plant in the world of heating, ventilation and air conditioning (HVAC).  HVAC equipment is designed and installed to provide a centralized heating and cooling system for a building or complex.

Central air conditioning set ups are commonly used in mid to high-rise buildings (5 or more floors), hotels, shopping centers, airports, entertainment centers, apartment complexes, and many other large commercial and residential settings.  In these places it is more practical to centralize HVAC equipment, rather than have local air conditioner units installed all over the building. There are hundreds of ways in which basic HVAC components can be assembled in order for the standard refrigerant cycle to heat or cool a building.