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Buying an Air Conditioner

Air conditioners have 3 functions. The lower the temperature, remove the humidity (moisture), and filter the air. To choose the air conditioner that will perform its purpose efficiently in the area, you will place it, several decisions have to be made before deciding on the right air conditioner for you. What type to buy: Window, Portable or Wall Unit, and Other Options. Window units are the most popular because they are efficient, most reasonably priced, and easy to install. Portable units do not need to be mounted in a window, so they are perfect for a room with no windows or only one window that you don’t want to block. They are usually on wheels and are vented through a hose placed in a window. Wall units are placed in holes cut into exterior walls.

Size of Unit:
Make sure the unit is the right size for your window or wall opening
Size of the Room is Important: An air conditioner must have the right cooling capacity for space. A unit with too high cooling capacity can turn off and on too often. Many factors impact the power level necessary: - Height of the ceiling - Number of windows in the room - Is the room on the top floor - Are there many open doorways leading into the room - Is the window or wall unit going to be placed in direct sunlight - A room with computers or even a mini-fridge might require a more powerful machine.

BTU’s.
Also known as British Thermal Units, this measures the cooling units per hour; higher BTUs mean more cooling capacity. Energy Efficiency Rating (EER).
The EER is required to be displayed on modern air conditioners. Units with higher EER ratings use less energy.
Adjustable louvers: The air conditioner must direct the flow of air to the center of the room. So, unless the window is exactly centered, the vent will need to be adjusted to the optimal position to get the air flowing to the right spot. So, look for a unit where the louvers can be moved up, down, left, and right.

Features to Look For:
Remote control devices allow you to change the settings from across the room. Timers allow you to set different power levels or have the unit go on and off at different times of the day. Removable filters allow you to remove dust and keep the air conditioner running optimally. Digital temperature settings are usually more accurate than a dial or button.
Google It.
Read reviews from reliable sources and consumer sites and make sure that the unit you are choosing has favorable ratings.

Window vs. Portable and/or Wall Units and
Other Options:
Window Units: This type of unit is the most popular because it is efficient, affordable, and easy to install. It can cool a room by itself or as a supplement to a central system. A window unit can be installed into single or double-hung windows, sliders and casements, depending on the model. Make sure that it will fit the window it is intended for (style and size), so take the measurements of the window carefully and compare them to the specifications of the unit. Also, check that the outlet in the room matches the type of plug the unit comes with. A window unit usually comes with accordion panels to make sure the air conditioner fits securely. Models made for sliding windows will need support on the outside of your home. A window unit is installed into an open window with the hot exhaust facing outside and the cool return facing inside. The best window in which to install this type of unit would be one that is located in a shady spot. An air conditioner can come with a fixed or slide-out chassis. The chassis is the frame the surrounds the unit itself. A slide-out chassis can be installed as a window unit or a wall unit. The fixed chassis can only be used in a window. One added benefit of a slide-out chassis is that the mechanics are easily accessible once you slide the unit out of its chassis and this allows for easy maintenance and cleaning.

Portable Units: This type of air conditioner is more flexible in that it can be used anywhere and moved from room to room. It is useful for a room that has one or no windows. In addition, many buildings don’t allow units to be placed in the windows, so portable is the only solution. However, a portable air conditioner can be quite heavy so make sure it comes with wheels for easy maneuvering. If you plan on using it in a carpeted room, moving it can be quite strenuous. This type of unit uses the air from inside the room to cool the condenser. If you can either exhaust the hot air back into the room or out the window, via a hose through a window, sliding door, wall, or ceiling.Water accumulates when the air conditioner draws in hot air. It can be drained in a few ways. Some models have a reservoir that holds the water that was removed from the humid air. The water tank needs to be emptied every few hours or daily, depending on how hot the air is. In self-evaporating systems, the water condensation is recycled back into the air. For this type of water removal, there are single or double hose venting options. Single Hose Air Conditioning Units - This pulls warm air from the room, sends it past coils cooled by the refrigerant, and then sends heated air and moisture through the hose and out of the window. A problem with this is that negative air pressure is created. This may actually pull hot air into the home through any cracks or loose fittings. If the area being cooled is very big, the machine will have to work much too hard to cool the room. But if the area is not large, then the one hose system can be a good option. Dual Hose Air Conditioning Units - This model has an intake hose and outtake hose. The air inside the room is drawn into the unit where it is cooled down and then sent back into the room. To cool down the unit that generates a lot of heat, an intake hose pulls air from outside the home and delivers it to the air conditioner to keep it cool. Then, a second hose sends all of the warm air out of the home, through the window. The dual hose system doesn’t have to work nearly as hard as the single hose option. For this reason, if you have a larger space, the dual hose A/C unit is a better choice. The dual hose machine eliminates the negative air pressure problem. However, it is slightly more expensive. It cools the room more quickly but it requires more electricity. Something to note is that most portable units do not cool as well as advertised. And they use more energy than other types of air conditioners.

Wall Units: This type is similar to the window unit. The difference is that the wall unit is placed in an opening in the wall and not in a window. It requires a sleeve that the unit will sit inside. A sleeve is a metal box the holds the air conditioner and supports its weight. You need to check that the sleeve you have fits the wall unit you are going to purchase. This type of unit is usually available with a more powerful cooling capacity than the other 2 types of units. They are also airtight and fit securely ensuring that hot air is not leaking into the room.

Other Options
Split Air Systems:
This type of air conditioner consists of an outdoor unit and an indoor unit. The outdoor part is installed on or near the wall outside of the room where the system is being installed. That consists of the compressor, condenser coil, and the capillary tubing. The unobtrusive indoor unit contains the cooling coil, a long blower, and an air filter. A split air conditioner does not require ducts. The indoor and outdoor units are connected with a set of electrical wires and tubing. Ductwork (as in central air conditioning units) usually increases energy costs because a lot of energy is lost due to heat exchange in the air duct system. This is not the case in a split air system that has no ducts. The split air conditioner system runs relatively quietly. The parts of an air conditioner that make the most noise are the compressor and the fan that cools the condenser. In a split system, the compressor and fan for the condenser are located outside of the room, unlike window and wall units. Another benefit is that you can have more than one indoor unit connected to a single outdoor unit. This makes it easy to cool multiple rooms or a large room through the use of two indoor cooling units and only one outdoor unit. The cost of this kind of air conditioning unit is significantly higher than a window unit and it requires professional installation. However, you will save on your energy bills and the unit will usually last longer than other types of units.

Heat/Cool Air Conditioners: There are areas where installing a large central air unit creates a greater expense than the need requires. By the same token, heating units require costly purchases of oil or propane. In some places, the mildness of the temperatures for most of the year makes these types of systems excessive. Sometimes, even in homes with a large HVAC system, there are rooms that do not get the heat and/or air conditioning they need. This happens in converted garages, attic rooms, etc. A window A/C unit that provides both heat and cool air can save money and still allow for a comfortable temperature in the home and/or room all year-round.

BTU’s This is a measurement (British Thermal Unit) that indicates how much heat the air conditioner can remove over an hour. However, bigger is not always better. While it is true that an air conditioner with insufficient power for the room will not cool it, an overpowered unit that cools the room too quickly will not have enough time to dehumidify the air as well. This can result in a room with a cold and clammy feel. In order to measure how many BTUs your area needs, you need to calculate the square feet of the floor, the ceiling height, and various other issues that are listed above (see Size of the Room is Important).

Below is a table that indicates BTU’s based strictly on square footage.
SQ Feet BTU

100 - 150
151 - 250
251 - 350
351 - 450
451 - 550
551 - 700
701 - 1,000
1,001 - 1,200
1,201 - 1,400
1,401 - 1,500
1,501 - 2,000
2,000 - 2,500

5,000
6,000
7,000 - 8,000
9,000 - 10,000
10,000 - 12,000
14,000
18,000
21,000
23,000
24,000
30,000
34,000

Generally, an air conditioner needs about 20 BTU per square foot of space. Multiply the length of the room by the height to get the number of square feet. Add in the size of any attached rooms that are not separated by doors. If the room is very shady, you can reduce the capacity needed by 10 percent. If the room is sunny, add 10% capacity. If the room is occupied by more than 2 people a majority of the time, add 600 BTUs per person. If the area being cooled is a kitchen, add 4,000 BTUs.

Energy Efficiency:
EER is a number that measures the amount of energy needed to deliver a given cooling capacity. The higher the EER number, the lower the relative energy use. While a unit with a lower EER rating will cost more, it will save money in the long run by reducing the cost of energy bills. Energy Star Certification: An energy star label means that the unit meets the strict energy efficiency guidelines set by the US Department of Energy. It indicates that the unit uses less energy than a similar unit without the label.