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A Guide to Learning, Exploring, and Purchasing an Air Conditioner

This article will help you learn everything you need to know about air conditioners.

Home air conditioners are appliances that are designed to make the air in your home more comfortable. The basic thing that most people think of when they hear "airconditioner," is a device that cools down the air in a room to make the people in the room more comfortable during hot weather.

All kinds of air conditioners take extra moisture out of the air and some of them filter particles (such as pollen and dust) out of the air, in addition to cooling the air. An appliance that only takes moisture out of the air is called a "dehumidifier." Dehumidifiers often simply vent the warm air right back into the room. Appliances which filter or otherwise clean particles out of the air are called "air filters" and "air purifiers." Most of them do not heat or cool the air.

The basic air conditioner works in almost the same way as your refrigerator, except that it blows the cold air out into the room instead of holding it inside an insulated box. The simple explanation of how an air conditioner works is to say that the device moves heat from one place and puts it somewhere else. That's what all the tubes, and fans, and noisy parts are for.

An air conditioner on its own makes your house more comfortable during hot weather, by keeping the air nice and cool. Are there small children, elderly people, or pets in your home? The cooler air helps keep them safe.

Small children and the elderly have a harder time keeping their bodies at a safe, healthy temperature, and an air conditioner helps them do this. In the same way, the cooled air helps to keep your dogs, goldfish, and ferrets from getting heatstroke. Since all air conditioners dehumidify, yours will help prevent mold and mildew from taking over your home. The dehumidifying aspect of your air conditioner can also prevent water damage to wooden floors and furniture when the weather is muggy.

  • Portable - These are the ones that can be wheeled around the floor and set up without much - or any installation.
  • Window - These are the box-like devices that stick out of windows on apartment buildings in many cities, and are the first thing people picture when they think of "ACs."
  • Split - These are a clever hybrid between a window air conditioner and central air.
  • Central - These are the most common kind for large office buildings and schools, with ductwork through the building.

Pros and Cons

The type of room you're planning to put it in will make a big difference to what model of air conditioner is right. The perfect unit for a small home office with an eight-foot ceiling isn't likely to work well at all for an open-concept combination of kitchen and living-room with cathedral ceilings and south-facing picture windows.

The intended location will determine how quiet the unit needs to be, how much humidity it needs to take from the air, and how large an area it needs to cool.

Pros Cons
Portable Air Conditioners
  • Energy Efficiency
  • Cost
  • No Installation
  • Easy to Move
  • Relatively small area
  • Frequent maintenance
  • Floor Space
Window Air Conditioners
  • Perfect for high-humidity rooms (eg. Kitchen)
  • Easy Installation
  • Efficient
  • Programmable
  • Requires a suitable window
  • Obstructs the iwndow
  • Usually less efficient than a portable model for low-to-mid humidty conditions
Split Air Conditioners
  • Some can serve several rooms at once
  • Takes up less interior space
  • Installation is easier than for central air
  • Requires an outdoor location for main unit
  • Installation includes drilling through walls
Traditional Central Air Conditioning
  • Can serve entire building
  • Convenient
  • Can combine heating and cooling in one unit
  • Expensive
  • Complicated installation
  • Most of the maintenance needs to be done by a pro

By Type of Room

Room Best Air Conditioner Why
KitchenWindowEfficient, and directs mositure right outside
Home OfficePortableMoveable, quiet, doesn't require renovation
BedroomPortable or SplitQuiet, efficient
NurserySplitQuiet, no cords, and can't be climbed upon
WorkshopPortableCan be moved to exactly where it's needed
Living-roomSplitQuiet, and no cords to trip or fray
BathroomWindowVents moisture directly outside
Whole HouseCentralEfficient, can combine with heating, convenient
ApartmentPortableCan be used with odd window shapes and without damaging or altering the walls

BTU Information

Quite possibly the most important consideration when choosing an air conditioner is its "size." This isn't the physical size of the device itself, but rather the number of "BTUs" it puts out.

"BTU" stands for "British thermal unit." This is a unit of measurement equal to 1054.4 joules. (Weisstein, 1996-2007) It is a way to measure how much energy is needed to heat something. Calories are another such unit of measurement. A single BTU is enough energy to heat or cool a pound of water by one degree Fahrenheit. In the case of air conditioners, the BTU rating tells you the amount of heat they can take out of a room in an hour. For example, 12,000 BTUs are equal to one ton of cooling capacity. That's a lot of cooling.

To determine how many BTUs you need, first figure out the area of the room in square feet. As you probably remember from school, the area of a square or rectangle is calculated by multiplying the length times the width, in feet. If there is a triangular area, figure it separately: length multiplied by width, then divided by two. A room with a complicated shape can be figured out by sketching out the shape and marking off square and triangle sections. Measure and calculate them separately, and then add the areas together at the end. Once you have calculated the area, take a look at the room-size chart below.

Area To Be Cooled (square feet) Capacity Needed (BTUs per hour)
100 up to 1505,000
150 up to 2506,000
250 up to 3007,000
300 up to 4008,000
350 up to 4009,000
400 up to 45010,000
450 up to 55012,000
550 up to 70014,000
700 up to 1,00018,000
1,000 up to 1,20021,000
1,200 up to 1,40023,000
1,400 up to 1,50024,000
1,500 up to 2,00030,000
2,000 up to 2,50034,000

Regular maintenance of your air conditioner will keep it in working order for years to come, and will save you money on repair costs. The basics are similar for all types, with minor variations.


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