Home air-conditioning systems come in several designs, ranging from massive central systems operated by an outdoor compressor to small portable room units that operate as freestanding floor units or window-mounted appliances. No matter what form they take, air conditioning systems all have some basic design engineering in common. All systems include refrigerant, a compressor, condenser, expansion valve, and evaporator coil, as described in How Air Conditioning Works.
In this tutorial, we will review the most commonly used air conditioning and cooling systems in the home and their terminology. Be sure to also review the Top 7 Air Conditioning Tutorials You Need to Read
Window Air Conditioners
A window air conditioner is technically called a "unitary" air conditioning system and consists of a self- contained air conditioning unit that is placed in a window or, rarely, through a hole in an exterior wall. Since adding holes in your home’s outside walls are not a really good idea, these units are almost always placed in a window unless there is an overriding reason to mount it through the wall. The unitary system has all the refrigeration components in one compact box. It ejects heat out one end (the outdoor side) and blows cooled air out indoor side.
Window air conditioners come in many sizes, some large enough to cool a substantial space, such as an entire floor.
A very small home can be adequately cooled by a larger window air conditioner, especially if it a one-story home.
Portable Air Conditioners
This system is another flavor of the unitary air conditioning system. The portable air conditioner consists of a mobile, self-contained air conditioning unit that is placed on the floor inside a room and discharges exhaust heat using a hose vent through an exterior wall or window vent.
Portable air conditioning units are a bit noisier than other types of units and are typically suitable for room less than 500 square feet in size. These units are a solution to those stubborn hot rooms or when it's not practical to install a window-mounted unit. Like the window air conditioner, the portable unitary system has all the refrigeration components in one compact box.
Because the portable unit sits indoors, its evaporator fan runs fairly constantly in order to evaporate the condensed moisture that collects within the unit. This is quite different from a window mounted unit, where condensed moisture can drip away onto the ground.
Split (Ductless) Air Conditioners
The split system or ductless system is technically called a "packaged terminal air conditioner" or PTAC. You see these occasionally in home applications but more commonly in hotels, motels and apartments. But it is increasingly popular option in homes that are not served by a forced-air HVAC system, such as those heated by steam or hot water boilers.
The split system breaks the air conditioning system into two packages or terminal units, often located quite some distance apart. Refrigerant tubing passes through the wall connecting both package units.
One terminal package is the condensing unit located on the exterior, which includes the compressor, condenser and condenser fan. The other terminal package is the evaporative unit located on the interior, which handles air cooling and distribution. The internal evaporative unit includes the fan, expansion valve and evaporator coil, and is usually a rectangular box unit mounted high on an interior wall.
Central Air Conditioning
A central air conditioning system is the premium cooling solution for your home. It is the quietest, best performing and most comfortable. The biggest issue is making sure the system is sized appropriately for your home. If it is sized too large, it will not perform well and will not adequately dehumidify. Proper maintenance of a central air conditioning system is also very important.
A central air conditioning system is made up of two packaged units, the condensing unit and the evaporative unit. They are connected to one another by refrigerant tubing. The condensing unit is the large boxy unit that sits outside and consists of the compressor, condensing coils, and condensing fan. The evaporative unit typically sits in the plenum of your furnace so the air conditioning can use the same ductwork as your heating system. Within the plenum, the evaporative unit consists of the evaporator coil and expansion valve.