Informational Guide

How Do Portable AC Units Work?

AC units provide cold air comfort to homes around the world. Learn how portable air conditioners work and function to keep you cool.

by Ian Haynes

Air conditioning has been around for over 120 years. Portable air conditioners less than 80 years. In that time, we have watched the components become more powerful, more compact, and lighter.

With energy efficiency, low cost, minimal maintenance, and the ability to move from room to room, portable air conditioners are key to home climate control. This article will explain exactly how they work and why they are a reliable solution to your home’s humidity and heat concerns.

During the time of World War I, the refrigeration industry was still in its infancy. Many larger commercial areas had air conditioning, such as theaters and auditoriums. Residential air conditions were also starting to become more popular.

This was due mostly to the advances in refrigeration by Willis Carrier, the namesake for the first (and one of the largest) air conditioning manufacturers in the world.

It wasn’t until Frederick Jones, an engineer, Army veteran and inventor, developed refrigeration to be used in trucks, did portable air conditioning even enter the idea stage. Jones invented the Thermo King, which allowed frozen produce to be shipped great distances.

After his newly founded company earned multi-million dollar status, Jones also invented smaller refrigeration options for military vehicles. This allowed the storage and transportation of vital blood for wounded soldiers on the battlefield. His inventions saved thousands of lives.

Jones wasn’t done yet, though. With over 60 patents and 100s of inventions, his primary focus was on refrigeration. His ideas and advances in the field allowed those that came after him to continue his ideas and theories, producing residential air conditioners that were small, affordable, and portable.

Types of Portable Air Conditioners Explained

When it comes to portable air conditioners, there are a few different types, from single hose to dual hose and even portable ACs without a hose. Each type has its own advantages and disadvantages. Let’s take a closer look at the various types of portable ACs.

Single Hose

Single hose air conditioners are the basic type. They are considered the “original” design and are still among the most popular of the three versions. While the various options are different, the biggest difference is, of course, the number of hoses.

In a single hose system, the hose is responsible for exhausting the hot air and heat created by the machine from inside the home. Air is brought in through intake vents (usually located on the back) and passes through a filter.

The air is then moved over and through the evaporator coils, where it is cooled and sent back into the room through the front or top louvers. This process does three things. First, it cools the air in your home, making the space more comfortable.

Second, it created humidity and heat that must be exhausted. The exhaust is pushed out of the home through the hose. This hose is connected to a window sleeve that blocks air and debris from getting in from the outside.

Third, the humidity condensates, resulting in water droplets that end up in a collection pan. Most models have the collection pan near the hottest part of the machine. This induces evaporation, where the warm, humid air is taken outside through the hose.

In some models, you will need to remove the collection tray and empty it manually. Still, other options include a drain hose that you can connect to and allow the system to drain into the tub, toilet, or outside.

Single Hose Advantages
  • Ideal for smaller rooms, apartments, or condos.
  • Can maintain temperature quite well.
  • More affordable than the other options (on average).
  • Some models also include heating capabilities.
  • Washable filters minimize maintenance.
Single Hose Disadvantages
  • Can create a vacuum, pulling in hot air through improperly sealed doors or windows.
  • Not as energy-efficient as dual hose models.
  • Manual draining of the condensate can be difficult.
  • Doesn’t offer the high mobility of a ventless model.
Dual Hose

Dual hose portable air conditioners work in much the same way as the single hose versions. This newer and more advanced form, though, has some distinct advantages.

The units bring in air from the outside through the intake hose (or hoses), where it is sent through the normal air conditioning process of heat exchange. The cold air is then passed into the room as cool, clean air.

The heat created by the machine and the humidity and warmth removed from the air is then pushed back outside through the exhaust hose. Unlike a single hose unit, dual hose models don’t rely on recycling the air already in the room.

This means you don’t have to worry about creating an air vacuum in the home, and you are less likely to pull in warm air through cracks or improperly sealed windows and doors.

The machine itself is also highly efficient. It doesn’t have to work as hard to cool the air and runs for short amounts of time, producing more cool air and maintaining the temperature for longer periods.

While the initial investment may be higher than the other model types, you are paid back for that cost through savings in your energy bill.

Dual Hose Advantages
  • More efficient than the other types.
  • Ideal for larger spaces and multiple rooms.
  • Doesn’t cause a vacuum.
  • Less condensation to drain or clean up.
  • Maintains set temperature longer.
  • Generally has a longer life expectancy per model.
Dual Hose Disadvantages
  • Higher initial cost.
  • Must be used in a room with a window.
  • It can be heavy and difficult to move.
  • More maintenance required.
Ventless

If you want to get technical, ventless portable air conditioners aren’t air conditioners. Evaporative coolers are more of what they are. Inside the body is a tank or bucket that you can fill with water.

When the unit is powered on, the air is drawn in from the sides or read intake vents. After it passes through a screen filter, it is then drawn through, over, or around the water. In some models, this is all there is.

Other models pipe the water through coils that the air is then passed through. A nominal heat exchange takes place where the water removes some of the heat from the intake air. The cooler air is then fanned out into the room.

Because there isn’t any refrigeration used, there isn’t a need to vent the exhaust. The air is brought in, cooled, and pushed out. These units are pretty efficient and can cool smaller spaces pretty well.

The full water tanks make them a bit difficult to move when full, though, so you want to move them before filling. The maintenance is also slightly higher since you need to empty and clean or dry the tank after use to prevent mold growth.

However, for small spaces or rooms without windows for vent hoses, they make the ideal cooling apparatus.

Ventless Advantages
  • Great for rooms with no windows.
  • Can be used in almost any space.
  • Indoor and outdoor models are available.
  • Use less energy than other types.
Ventless Disadvantages
  • Doesn’t cool as well as other types.
  • Must run longer to achieve desired temperatures.
  • Highest maintenance of all types.
  • Adds humidity and moisture to the room.

Parts of all Portable Air Conditioning Units

You won’t find the difference between a central air conditioner and a portable air conditioner in their list of parts. However, knowing those different pieces will help you understand how they work and can aid in troubleshooting. Let’s take a look.

Compressor

The compressor works as the heart of the system.

It is responsible for all refrigeration movement.

The refrigeration cycle can continue over and over by taking the cooled refrigerant gas and compressing it into a hot liquid.

Condenser coils

The condenser coils are the backside coils that take the heated refrigerant gas, cool it off, and send it to the compressor.

The heat removed from the gas is the same heat absorbed from the air in your home.

Evaporator coils

Evaporator coils are the smaller, colder coils that cause the primary heat exchange between the colder high pressured liquid refrigerant and the warm air from your home. As the heat is absorbed by the refrigerant in the coils, it expands into a gas and heats up, pushing its way to the condenser unit.

Vent hose

The vent hoses are the large hose or hoses connected to the rear of the unit and run to the window housing.

In a single hose AC the hose acts as the exhaust only with intake vents located on the back or sides of the machine.

For dual hose systems, the hoses are intake and exhaust capable and work to prevent room vacuums and overheating.

Vent fan

The vent fan is the fan responsible for suctioning the heat released by the condenser coils and pushing the hot air outside through the vent hose.

This fan is internal and generally does not have a filter as the exhaust vents directly outside.

Blower

Blower

The blower or blower fan is the fan responsible for pushing the cold air into the room.

After the intake air is passed over the coils and cooled, the blower picks it up (cold air is heavier) from the coils and distributes it into the room through the front louvers.

Temperature control

The temperature control settings are found on the control panel.

This panel is usually located on the top or front of the unit and on any remote control or mobile app used for the portable AC.

This panel is where you will select your mode, fan speed, temperature settings, and, if available, power controls and louver oscillation.

Case

The case is the plastic housing that contains all of these parts.

Colors, styles, and vent or filter locations will vary by brand and model.

Most cases will come with wheels, handles, or both to assist in transportation and portability.

Expansion valve

The expansion valve is a small device located on the high pressure refrigerant line just after the compressor.

Its job is to relieve some of the pressure on the liquid refrigerant.

Once the liquid passes through the expansion valve, it is slightly cooler and ready to expand into a gas in the evaporator coils.

Common Features Found in Portable ACs

Portable ACs have several features that help you decide to buy that particular brand or style. The most common features are listed here.

Timer

A timer function allows you to set the unit and forget it. It will turn off after a specified time (usually in an hour or 2-hour increments). This is an ideal feature for those who like to have a room cooled while you fall asleep or get ready in the morning but don’t want to have the unit run all night or while you are not home.

Remote

Remote control operation is great for those that have their system set up on the other side of the room. You can usually find all functionality and operational features on the remote as well as the control panel.

Some models will also connect to the home wireless network and enable remote operation through a mobile app.

Fan

Fan mode is a feature that you will find on almost every model. It allows you to use the portable AC unit as a fan instead of an air conditioner. This will help keep air moving through the room without wasting a lot of power or energy consumption running the AC components.

Auto

Auto mode allows the machine itself to decide what is best for the room. Everything from fan speed, timing, temperature, and even oscillation can be controlled by the auto mode (depending on the model and capabilities).

Dry/Dehumidify

Air conditioners are natural dehumidifiers, as they pull the heat and humidity from the air in the evaporator. However, some models allow you to run only the dehumidify function, collecting moisture from the air that is then stored in a collection tray or sent through a drain tube connected to a tub, toilet, or basin drain.

Oscillation

Most portable units don’t move when running. However, a select few will have pivoting louvers that will adjust automatically up and down or even left and right. This allows for oscillation of the cold air output and distribution around the room instead of in one single direction.

How do Portable Air Conditioners Work

With very few exceptions, all air conditioners work under the same principles. Known as thermodynamic principles, these laws govern heat exchange, condensation, distribution, and temperature.

On any scale, the physics always apply, and in a portable air conditioner, the principles hold true just as they do with larger systems, just on a smaller scale. So how do portable air conditioners work to cool your home?

When you turn the system on, a chain reaction of events begins to occur, and it all starts with the air intake. Wither through an intake hose or intake vents, warm air from outside the home or in the room is drawn into the case.

Inside the case, the air is cooled and condensed, where it is then blown into the room resulting in a lower temperature.

What Happens Inside the Case

Everything happens because of the refrigerant. This synthetic material is constantly undergoing state transformations, from a high pressure liquid to a low pressure gas. Starting at the compressor, the gas is compressed until it reaches a state of high heat liquid.

The pressure created by the compressor pushes the liquid refrigerant through the copper coils to the thermal expansion valve.

The valve releases some of the pressure on the liquid, which causes it to rapidly cool, again pushing it even further into the system. When this cooled and low pressure liquid reaches the evaporator, it is sent through a series of copper coils, where it expands even further, turning from a liquid into a gas.

At this point, the refrigerant is extremely cold. When the intake air is brought in and passed through the coils, the heat from the air is collected by the refrigerant while the moisture in the air condenses on the evaporator fins.

The moisture drains into a collection tray or passes out through a drain hose, and the cool air is sent to the blower to be distributed into the room.

Completing the Cycle

Back inside the case, the gas refrigerant in the evaporator coils is now hot. Having collected the air’s heat, it is sent through the remainder of the coils into the condenser unit.

The condenser is another series of copper coils where cooler air is blown over them, causing the gas refrigerant to once again go through a heat exchange. This time the heat is removed from the refrigerant into the air.

The warm air is then vented out the exhaust hose to the outside of the home through the window. The cold gas refrigerant once again enters the compressor, where it is compressed into a high heat liquid state and the cycle repeats.

Portable vs. Other Air Conditioners

Now that we have a better understanding of how portable ACs work, let’s find out how they compare to other types of air conditioner systems.

Central AC Units

Central air conditioners are the most popular and widely used AC systems in the country. The processes are the same, using the evaporators and condensers to cool the air in your home.

The biggest difference is the size, of course. Central systems and central split systems have separate condensers and evaporators. The most common setup is a large condenser mounted outside the home, with the compressor and condenser fan and coils all in a single housing.

Inside the home, the copper lines run the refrigerant to the evaporator, usually located in an attic, closet, or bathroom ceiling. Central ACs use ducting to move the cold air to each room. Vents and louvers in the rooms can be adjusted or shut as needed.

Aside from the size and split components, central ACs are also controlled by a central thermostat, must be installed by a licensed professional, and can cost thousands of dollars for an initial install and several hundred for repairs.

Mini Split AC Systems

Mini Split AC systems come in two varieties. Ducted models are generally used when upgrading or replacing a central air system, and ductless mini-splits are typically installed as a stand-alone solution.

Both types use a heat pump. This is an external device, much like the condenser in a central air system. It has a 2-way pump and motor, which reverses as needed to remove heat from the house or add heat to the home.

The most significant difference, though, is the interior. Instead of venting like a central system, or a small unit like a portable air conditioner, mini split systems have wall mounted evaporators and fans. These small units are individually controlled with remotes or mobile apps and, once mounted, cannot be moved.

While they are among the most efficient cooling systems, they are designed to cool a single room at a time (per inside unit), but unlike a portable AC, they cannot be moved from room to room when needed.

Window AC

Window units are smaller air conditioners, like portable units. However, they are not very portable. Window units are designed to be all-inclusive but are not lightweight. They sit in your window, with the weight of the top half holding them in place.

Like a portable model, window (and through-the-wall) models are compact, with all air conditioner parts are inside the case. The exhaust vents outside the window while the cool air is blown inside the room.

Also similar to portable ACs, window units are only designed to cool off one or two rooms. While higher BTU units can cool a large square footage, the cool air doesn’t go through or around walls and doors.

While window units tend to be more powerful than portable models, this isn’t always the case. However, they also tend to cost more and require you to block off an entire window while the unit is installed. With portable units, you only need to block the window off while the machine is in use.

How to Vent a Portable Air Conditioner

Proper venting of your portable AC is critical to the machine’s efficiency, how well it works, and the ability to lower the temperature in your room. To ventilate the AC, you will need to connect the venting hose (or hoses, in a dual hose model) to the back of the unit.

The other end is connected to the window block. It sits in the window frame to block airflow through the window. The windowpane sits on the window connector, so there are no screws or permanent mounting required.

Once the machine is properly vented, you can use it efficiently. The venting is needed to prevent the warm exhaust air from reentering the room. If the hot air is mixed with the cold air in the room, the unit must continually work harder to produce cold air.

Not only does this increase the cost of running the unit, shorten the life of the air conditioner, but your room won’t get colder. It is always wise to ensure the air conditioner is adequately vented before turning it on.

Keeping Portable ACs in Tip Top Condition

To keep your portable air conditioner functional and operating at the highest efficiency, proper care and maintenance are critical.

The following steps will help make the machine more efficient, longer lasting, and lower your overall maintenance regimen.

  • Ensure all the hoses (vent, drain, etc.) are correctly attached and secured.
  • Make use of the automatic settings and timer features to minimize usage.
  • Ensure the AC is located away from heat sources like windows, refrigerators, and appliances.
  • Keep the drain lines clear, straight, and flowing.
  • Turn the unit on before the room’s temperature rises too high.
  • Keep windows, doors, and curtains closed to minimize heat absorption.
  • Ensure the capabilities of the air conditioner match the room size.

People Also Ask (FAQ)

Can I use a portable air conditioner in a room without a window?

It is not recommended to use a portable air conditioner in a room without a window for venting. However, it can be done in a pinch. The problem is that you still need to vent the exhaust. This can be done by running the vent hose into a bathroom, closing the door as much as possible, and turning the exhaust fan on.

If the bathroom isn’t an option, you can also buy extension hoses and run the exhaust to another room, out a door, or other option. The main thing is to vent the unit to a room you don’t need to be cooled. The other solution is to purchase a ventless portable air conditioner instead.

Do portable air conditioners need refrigerant?

Yes. Any air conditioner requires refrigerant. Without refrigerant, you can only cool the air to your heat exchange source’s temperature, such as water in an evaporative cooler. If the unit doesn’t use a refrigerant with the condensing and evaporation stages, it is just a cooling fan, which may or may not actually lower the room’s temperature.

What voltage do portable air conditioners require?

Almost every portable air conditioner is designed to run on standard household outlets. This is a requirement of 110 – 120 volts. Some larger models will require dedicated 220-240 volt circuits, though these are usually reserved for window units or through-the-wall models.

How long is the exhaust hose that the portable air conditioner comes with?

The vent hoses will vary in length and flexibility between brands and models. On average, you can expect the vent hose to be between 3 and 4-inches in diameter and 4 to 6-feet in length. This doesn’t give you a lot of playroom for positioning, but you can purchase extension hoses or couplers to link multiple shorter hoses together.

What happens if you don’t drain your portable air conditioner?

What happens when the portable AC drain isn’t emptied or connected to a drain hose will depend on the model and its features. Some models will do nothing, and the tray can overflow, causing water leakage and floor damage. Other models will have sensors that alert you that the tray is full, and some of those models will shut off until the tray is empty.

It is essential to understand the safety features of the model you are thinking of buying before you purchase so you know what to expect and how much extra maintenance may be involved.

How energy efficient are portable air conditioners?

Portable air conditioners measure energy efficiency, just like everything else. The BTU rating, along with the wattage input, convert to the SEER (seasonal energy efficiency rating). The higher the rating, the more energy-efficient the portable ACs are.

Most portable ACs will fall between 7 and 10 on the SEER rating. This isn’t as high as some air conditioner types, but they also don’t pull as much power and wattage, either. On average, a portable AC with a SEER rating of 9 or higher can save you about $60 to $80 per year over models with lower SEER ratings.

How can I make my portable air conditioner work better?

While you cannot open the unit and rewires things to make it more powerful or colder, you can do things outside the case to help it cool the room easier and run less often. The use of ceiling fans and floor fans will help distribute the cool air through the room or to different rooms.

Other steps you can take include proper ventilation of the unit and sealing the windows or doors to prevent air leaks. You can also ensure the portable unit is located properly.

Keep it away from heat sources like direct sunlight, appliances, and areas with drafts. Finally, proper care and maintenance such as keeping the drain tray empty and the filter clean will all go a long way to making the unit perform at its absolute best.

What factors should I consider when looking for a portable AC?

There are several consideration factors to think about when purchasing a portable AC. The cost of the unit is the largest factor. Still, you also need to think about things like energy efficiency, dual or single hose, room size versus the AC capabilities, ventilation requirements, and power consumption.

The more features, efficiency, and capabilities, the higher the cost will be. However, paying a little more upfront for a better model will pay off in the long run.

Can I cool my garage using a portable air conditioner?

Portable air conditioners can cool any space that is within their capabilities. Knowing your square footage of the garage will go a long way. However, you also need to consider things like ventilation, open doors, windows, and other areas of air movement. While it may not be the most efficient method to cool your garage when used as a workspace, it can be done with the proper setup and higher BTU rated machines.

View more specific garage AC units here.

Conclusion

Portable air conditioners fill a hole in the home climate control industry. The ability to get cold air in the room or space without using the larger, more energy-consuming central air conditioners or purchasing and installing window units is a bonus.

This article gave you all the information on portable ACs that you need to compare them to different AC types. We also explained how portable air conditioners work, the parts needed, and troubleshooting techniques. Now, when you are ready to buy, you will be well informed and make a better purchasing decision.

Ian Haynes

Ian Haynes is a digital marketing specialist, writer, and researcher. He has worked on hundreds of articles relating to home cooling, heating and air quality with a vast knowledge of the technical aspects of these types of appliances. Outside of his work, Ian likes exploring Brooklyn with his Labrador. Learn more about the AC Lab team here.

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