Air Conditioners

Air conditioning is a combined process that performs many functions simultaneously. It conditions the air, transports it, and introduces it to the conditioned space.

Most air conditioning systems perform the following functions:

1. Provide the cooling and heating energy required

2. Condition the supply air, that is, heat or cool, humidify or dehumidify, clean and purify, and attenuate any objectionable noise produced by the HVAC&R equipment

3. Distribute the conditioned air, containing sufficient outdoor air, to the conditioned space

4. Control and maintain the indoor environmental parameters–such as temperature, humidity, cleanliness, air movement, sound level, and pressure differential between the conditioned space and surroundings—within predetermined limits

Parameters such as the size and the occupancy of the conditioned space, the indoor environmental parameters to be controlled, the quality and the effectiveness of control, and the cost involved determine the various types and arrangements of components used to provide appropriate characteristics.

Individual room, or simply individual air conditioning systems employ a single, self-contained room air conditioner, a packaged terminal, a separated indoor-outdoor split unit, or a heat pump. A heat pump extracts heat from a heat source and rejects heat to air or water at a higher temperature for heating. Unlike other systems, these systems normally use a totally independent unit or units in each room. Individual air conditioning systems can be classified into two categories: Room air conditioner (window-mounted)

Packaged terminal air conditioner (PTAC), installed in a sleeve through the outside wall The major components in a factory-assembled and ready-for-use room air conditioner include the following: An evaporator fan pressurizes and supplies the conditioned air to the space. In tubeand- fin coil, the refrigerant evaporates, expands directly inside the tubes, and absorbs the heat energy from the ambient air during the cooling season; it is called a direct expansion (DX) coil. When the hot refrigerant releases heat energy to the conditioned space during the heating season, it acts as a heat pump. An air filter removes airborne particulates. A compressor compresses the refrigerant from a lower evaporating pressure to a higher condensing pressure. A condenser liquefies refrigerant from hot gas to liquid and rejects heat through a coil and a condenser fan. A temperature control system senses the space air temperature (sensor) and starts or stops the compressor to control its cooling and heating capacity through a thermostat.

The difference between a room air conditioner and a room heat pump, and a packaged terminal air conditioner and a packaged terminal heat pump, is that a four-way reversing valve is added to all room heat pumps. Sometimes room air conditioners are separated into two split units: an outdoor condensing unit with compressor and condenser, and an indoor air handler in order to have the air handler in a more advantageous location and to reduce the compressor noise indoors. Individual air conditioning systems are characterized by the use of a DX coil for a single room. This is the simplest and most direct way of cooling the air. Most of the individual systems do not employ connecting ductwork. Outdoor air is introduced through an opening or through a small air damper. Individual systems are usually used only for the perimeter zone of the building.

New models are considerably more energy efficient than those made a decade ago. A yellow Energy Guide tag lists each new unit's energy-efficiency rating (EER) its capacity in British thermal units per hour divided by power consumption in watts. EERs for models now on the market range from about 9.7 to 12. A model with an EER of 10 should use about 20 percent less energy than one whose EER is 8, other factors being equal.

Window air conditioners made as of October 1, 2000, and rated at less than 8000 Btu/hr. are required to have at least a 9.7 EER. That's a big change from the old EER requirements of 8 for units under 6000 Btu/hr and 8.5 for units between 6000 and 7999 Btu/hr. Units rated between 8000 and 13,999 Btu/hr must have an EER of at least 9.8.

Fedders, General Electric, Sears Kenmore, and Whirlpool are leading brands of room air conditioners.

Buyer's Guide



Air Conditioners Air conditioning is a combined process that performs many functions simultaneously. It conditions the air, transports it, and introduces it to the conditioned space. Most air conditioning systems perform the following functions: 1. Provide the cooling and heating energy required 2. Condition the supply air, that is, heat or cool, humidify or dehumidify, clean and purify, and attenuate any objectionable noise produced by the HVAC&R equipment 3. Distribute the conditioned air, containing sufficient outdoor air, to the conditioned space 4. Control and maintain the indoor environmental parameters–such as temperature, humidity, cleanliness, air movement, sound level, and pressure differential between the conditioned space and surroundings—within predetermined limits Parameters such as the size and the occupancy of the conditioned space, the indoor environmental parameters to be controlled, the quality and the effectiveness of control, and the cost involved determine the various types and arrangements of components used to provide appropriate characteristics. Individual room, or simply individual air conditioning systems employ a single, self-contained room air conditioner, a packaged terminal, a separated indoor-outdoor split unit, or a heat pump. A heat pump extracts heat from a heat source and rejects heat to air or water at a higher temperature for heating. Unlike other systems, these systems normally use a totally independent unit or units in each room. Individual air conditioning systems can be classified into two categories: Room air conditioner (window-mounted) Packaged terminal air conditioner (PTAC), installed in a sleeve through the outside wall The major components in a factory-assembled and ready-for-use room air conditioner include the following: An evaporator fan pressurizes and supplies the conditioned air to the space. In tubeand- fin coil, the refrigerant evaporates, expands directly inside the tubes, and absorbs the heat energy from the ambient air during the cooling season; it is called a direct expansion (DX) coil. When the hot refrigerant releases heat energy to the conditioned space during the heating season, it acts as a heat pump. An air filter removes airborne particulates. A compressor compresses the refrigerant from a lower evaporating pressure to a higher condensing pressure. A condenser liquefies refrigerant from hot gas to liquid and rejects heat through a coil and a condenser fan. A temperature control system senses the space air temperature (sensor) and starts or stops the compressor to control its cooling and heating capacity through a thermostat. The difference between a room air conditioner and a room heat pump, and a packaged terminal air conditioner and a packaged terminal heat pump, is that a four-way reversing valve is added to all room heat pumps. Sometimes room air conditioners are separated into two split units: an outdoor condensing unit with compressor and condenser, and an indoor air handler in order to have the air handler in a more advantageous location and to reduce the compressor noise indoors. Individual air conditioning systems are characterized by the use of a DX coil for a single room. This is the simplest and most direct way of cooling the air. Most of the individual systems do not employ connecting ductwork. Outdoor air is introduced through an opening or through a small air damper. Individual systems are usually used only for the perimeter zone of the building. New models are considerably more energy efficient than those made a decade ago. A yellow Energy Guide tag lists each new unit's energy-efficiency rating (EER) its capacity in British thermal units per hour divided by power consumption in watts. EERs for models now on the market range from about 9.7 to 12. A model with an EER of 10 should use about 20 percent less energy than one whose EER is 8, other factors being equal. Window air conditioners made as of October 1, 2000, and rated at less than 8000 Btu/hr. are required to have at least a 9.7 EER. That's a big change from the old EER requirements of 8 for units under 6000 Btu/hr and 8.5 for units between 6000 and 7999 Btu/hr. Units rated between 8000 and 13,999 Btu/hr must have an EER of at least 9.8. Fedders, General Electric, Sears Kenmore, and Whirlpool are leading brands of room air conditioners.
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