How Does a Window AC Unit Work?

Most air conditioning systems are designed for larger spaces. This can either mean whole houses or big commercial buildings. Cooling down smaller areas, such as apartment buildings or individual rooms, can be a bit more challenging. This is because full-size central AC units are likely to be too powerful—and therefore too costly to run—for smaller buildings. This is why many people who live or work in smaller spaces turn to window AC units.

How does a window AC unit work, though? Is it different from conventional air conditioning? Is it practical for your building? In this article, we’ll explain some of the particulars so that you can decide if this alternative method of cooling is the right choice for your space.

Air Conditioning: The Basics

Regardless of their size, all air conditioners operate in essentially the same way. It all starts with a thermostat, which the user sets to their desired temperature. This thermostat is connected to a thermometer that measures the temperature in a room. It can use the information it collects to communicate with the AC unit. When the temperature climbs higher than the setting on the thermostat, it signals the device to cycle on, conditioning—that is, cooling—the air until the desired temperature is achieved.

When the unit is cycled on, it draws in air using a powerful fan. This air passes over evaporator coils, which contain a highly pressurized coolant liquid. Partially due to its natural properties and partially because it’s pressurized, the coolant has an extremely low boiling point. When warm air passes over it, it begins to evaporate back into a gaseous form. In doing so, the coolant draws heat energy out of the air, cooling it down and condensing it. The heat energy must have a safe place to be vented away from the AC unit. Usually, it is allowed to safely dissipate into the outside environment.

Once the air is cooled down, it’s then recirculated back into the building, where it gradually reduces the ambient temperature until the setting on the thermostat is achieved. The thermostat then signals for the AC unit to cycle back off.

After the air conditioner has switched off, heat energy from the outdoor air will begin to creep back into the building. This will have the effect of raising the temperature again, alerting the thermostat to turn the unit back on. This cycle will continue until either the outdoor temperature drops, the thermostat setting is changed, or the AC unit is shut off entirely.

The Equipment

Most conventional air conditioners consist of two parts: an indoor evaporator coil and a large outdoor condenser/compressor unit that circulates the pressurized coolant. Since they are quite large, these outdoor units aren’t a practical option for some buildings. For instance, there may not be enough dedicated space to install them for smaller buildings, such as apartments or small offices, and they can be costly to run.

A window AC unit essentially uses smaller versions of all the technology present in full-scale air conditioners, including miniaturized condensers and compressors. This emphasis on a smaller size means that a window unit sacrifices power for increased practicality in smaller spaces. Rather than two separate units, which there may not be room for, it is made up entirely of one single appliance that is installed—as the name suggests—in a single window.

Being made up of only one relatively small unit means that a window air conditioner has a few benefits over more conventional central air conditioning methods. First and foremost, it’s portable: you can uninstall it fairly easily for the winter, move it to a different window, or if you move, transport it to your next building. The smaller size also means it uses far less energy and is less expensive to run than full-size air conditioners.

Installing a Window Air Conditioner

To properly install a window AC unit, it’s important to choose the right window. Most air conditioners are designed for vertical sliding windows, which open upward. The window is opened and the AC unit is mounted underneath it. There must be plenty of room for the air conditioner to hang outside so that it can safely vent away waste heat without posing a hazard to any nearby buildings or property.

Window AC units may not work on other types of windows, such as horizontal sliding ones, although it’s not impossible. Another option in this case is a portable air conditioner with a specialized adapter in order to allow waste heat to properly be vented outside.

Is a Window AC Unit Right for My Building?

If you occupy a small space or just need to cool a small area, a window AC unit may be an excellent option for providing cooling. However, it is not without its downsides. For example, it requires a certain amount of outside space for the unit to hang. If you don’t have the space, you may not be able to take advantage of this method of air conditioning.

If your building is too large, or if you need to cool multiple rooms, a window air conditioner will not be the most efficient option. While they’re excellent for conserving energy in smaller spaces, they will often struggle greatly to provide enough cool air for any room that is too large. If you cannot find a window AC unit that is powerful enough for your space, you may have to consider alternative cooling methods, such as a central AC unit with an outdoor element.

If you decide that a window AC unit isn’t right for your building but a central AC unit won’t work either, you may still have options. Other cooling technology—for example, a heat pump—may be more effective. If you’re in the Portland-Vancouver area, contact the team at Entek HVAC to discuss the best heating and cooling options for your space.