How Does a Through-the-Wall Air Conditioner Work?

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Wall Units

Through the wall air conditioners are a cooling option for buildings that do not have central air conditioning installed. The units are relatively cheap. They typically cost anywhere from two hundred to four hundred dollars, depending on the size. Most units are designed to cool only one room, though some larger units may be able to cool additional rooms as well. No matter how large the unit, the ability to cool additional rooms is limited because the vent that blows cool air is only in one room.

Differences Between a Wall Unit and a Window Unit

Through the wall air conditioners look similar to window units. The major difference between the two is that the vents are on the back of the unit instead of the sides. A through the wall unit does not hang out of the wall like a window unit hangs out of the window. The back of the rear unit either sits flush with the exterior wall or hangs out minimally. The installation of a wall unit is more labor intensive and is usually considered more permanent than a window unit is. Window units install and uninstall quickly.

Advantage of a Wall Unit

One significant advantage that a wall unit has over a window unit is that it does not use up window space. When a window unit is installed, the window becomes unusable. With a wall unit, the window can still be used.


Through the wall air conditioners should be installed by a professional or a person that is very handy. A hole must be cut in the wall to install a wall unit. The hole should be of a size that allows the unit to fit snugly. For weather proofing reasons, space around the unit should be minimal. Each air conditioner comes with a manual that lists the size the hole in the wall should be. A metal sleeve is placed inside the hole in the wall. The sleeve comes with the wall unit. The sleeve provides structural support in the wall for the air conditioner. The air conditioner fits snugly inside the sleeve. After the air conditioner is installed into the sleeve in the wall, it is plugged into the nearest electrical outlet and weatherproof stripping is put around the air conditioner to prevent outside air and water from entering the building.

How a Wall Unit Works

A through the wall air conditioner works by sucking hot air from the room into the unit. The hot air that enters the unit is brought over the air conditioning condenser and cooled. The cooled air is pushed back into the room. The motor that runs the unit produces hot air. The air conditioner pushes the hot air from the motor out through the vents in the back of the unit so that it does not heat the room.

Installation Tips

1) Before purchasing the air conditioner, check the specifications on wall depth. Different models of air conditioners are different sizes. You want to make sure that the unit will fit in your wall. Some walls are too thick for some units.

2) The hole in the wall should be cut so that the air conditioner sits straight and level. If the unit sits at a tilt, it may not run properly.


H.C. Hisel

H.C. Hisel has worked for the past nine years as a professional writer, dancer, musician, painter and photographer. Hisel had her own weekly newspaper column in the Banana 411, a newspaper for kids. Her articles have been published in various print markets and online, including and