Air Conditioners

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A Guide to Understanding Air Conditioners

For days when fans just don't do the trick, air conditioners are very convenient appliances to have in your home. And the standard units aren't only used as room coolers anymore. They also dehumidify the air, making your indoor experience more comfortable.

Types of Air Conditioners

Window and through-wall units work well for individual room cooling. Unlike central air, they do not require any permanent installation. All installation supplies should be included in your unit purchase.

Unitary systems are the most common one-room air conditioners. They sit in a window or wall opening, and have completely interior controls. A fan blows over the evaporator, drawing heat from a room and discharging it into the environment.

PTAC (packaged terminal air conditioners) are common in hotels, because they have two separate units attached through tubing. This allows separate PTAC systems to independently set temperature preferences. Also, PTAC systems can be reversed into heating systems, retrieving hot air from outside and funneling it inside, unlike the air conditioning, which retrieves hot air from inside and funnels it outside.

Portable air conditioners have the benefit of not needing permanent installation. They can cool a specific region of a building. Some people rent them in cases of emergency, such as power failures in warehouses. All portable A/C requires exhaust hoses for venting.

Single-hosed units run a hose from the back of the portable A/C to the vent kit, where hot air can be released. These are ideal for small rooms, but they have lower cooling effect than other models.

Dual-hosed units are good for larger rooms. One hose vents hot air, while the other draws in additional air. With two hoses, hot air is expelled faster than in single-hosed units.

Split units are the most effective portable A/Cs. The compressor and evaporator are located separately, attached via two detachable refrigerant pipes. Also, with split units, no water ever needs to be drained from the internal unit. The compressor unit must always be located outside.

Central air conditioning, or central air, uses ducts to distribute cool air to more than one room in a building. This can be very costly to install and operate.

Important Air Conditioner Features

  • BTU: BTU, or British thermal units, is the listing on your air conditioning device that tells you how powerful the system is. The higher the BTU rating, the faster the unit can cool the air surrounding it. For bigger rooms, higher BTU is better. Of course, you don't want to get a BTU setting that is too high for a small room. This can cause your A/C unit to get to cold, which can damage it. Always consult the user's manual or a professional if you're unsure.
  • Extension kits: Most used on window units, extension kits are available for A/C units that do not completely fill the space in which they are installed. For example, a window unit may be too small for the window space it replaces. As a result, users will need an extension kit to properly fit the unit into the space and help avoid unnecessary ventilation. If you're unsure of how to do this or what kind of extension kit to use, consult a professional.
  • Insulation: OK, so technically, insulation is not part of the air conditioner. However, a room's insulation will dictate how well the room can cool down. With poor insulation, cold air easily escapes the room, defeating the air conditioning unit's purpose. Therefore, you should verify your home is well insulated to ensure the best performance from your A/C unit.

Air Conditioner Cost

Window-mounted air conditioners for rooms under 400 square feet are usually $100 to $300. For larger spaces, that price can go up as high as $800. Of course, added features, such as extra quiet settings, energy efficiency and remote controls will add more to the base price. Extension kits can add $30 to $100.

Through-the-wall models run between $250 and $600 for smaller room units, and upwards of $1,500 for larger rooms. Installation for these units will usually range just under $200. Again, more features mean higher prices. Portable residential units are usually between $400 and $650 for an average-sized room. Portable air conditioners for larger areas, as in the case of commercial-grade factories or spaces, can cost as much as $7,000.

Air Conditioner To-Do List

  1. Know the size of the room where your unit will go. With this room size, as well as the size of the window (if applicable), you can determine the right air conditioner for you, both in terms of size and in terms of power. Also, check the insulation. This can greatly affect the efficiency of your device as well as the worth.
  2. Check the direction of the room in relation to sunlight. For any air conditioners that use units entirely or partially outside, you don't want the sun to beat directly on the unit. This can cause damage and hamper the effectiveness of your device.
Last Updated: July 22, 2011
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About Emelie Battaglia Emelie Battagila is a contributing writer for

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