Portable air conditioners suck. Literally! You can convert single hose to dual hose portable air conditioners very easily. Here is why you should do so, and how to do it.

Types of Air Conditioners

Now if you’re like me and suffering in the sweltering heat that climate change has brought upon us, you may be looking for an air conditioning unit if you don’t already have one. You’ll undoubtedly be faced with purchasing one of the systems below.

Split Systems

These systems, also called ductless systems, consist of one to multiple indoor units connected to an outdoor heat-exchanger by piping containing the coolant. They can be independently controlled, are very efficient and, compared to ducted systems, far easier to install into a building as an afterthought.

https://upload.wikimedia.org/wikipedia/commons/c/c2/Multi-split-system.png
Multi-split-system (Air Conditioning)

Lesics has a very informative video on how these types of air conditioners work:

Central Systems

Central systems work on a similar principle, but rather than several indoor units, usually have a single heat-exchanger inside the central air distribution system, which cools down the air before transporting the air through ducts into the rest of the building. These types of systems have the advantage of also exchanging the air inside the rooms, but are generally very expensive and nigh impossible to install if not planned for in a building from the start.

Window Units

These types of systems air self-contained heat-exchangers that are easily installed in a window – provided it is the correct type. Flaps on the side allow the room to reduce the exchange of air from inside the air conditioned room with the outside air. This is paramount, as any air coming in from the outside will heat up the indoor air and thus require the AC to expend more energy to remove it once more.

File:Air Condition Unit Interior View USA.jpg
Single Room Air Condition Unit, interior view, USA

Their biggest drawback however is that they can only be installed in certain kind of windows. In Europe, Germany specifically, the windows are of a much different design compared to their US counterparts, and thus make the installation of a window unit impossible.

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Modern windows

Since winters in Europe can get very cold, most homes have double or triple paned windows for superior thermal insulation. A majority of the windows also only open up as a whole, thus making the installation of a window unit essentially impossible. As of yet there does not appera to be a market for window units for a European market.

Portable (Air-to-Air or Monoblock) Units

This leaves us with the last category. If you, like me, cannot install a split or central system because you don’t actually own the house, and because you have weird windows cannot use window units, you are left with either suffering in the heat or using a portable air-to-air unit.

single hose portable air conditioner - Greatly improve portable AC unit efficiency
Mobile AC with vent hose

They truly are the worst of the bunch. The principle remains the same – ambient heat is removed from the room air and dumped into air that is then vented outside. However, this method comes with a vast array of drawbacks.

  • Since the unit’s heat exchangers are not outside, they need a hose to vent the excess heat. That hose needs to be installed in a manner that reduces the amount of hot outside air to be leaked inside. This in of itself can be a nightmareish undertaking.
  • Since the compressor and the fans are inside, they can be quite noisy. The air inside the vent hose can also create a lot of noise due to turbulences.
  • The worst drawback however is the design of 99% of the available, commercial units…

Why They Suck

The required vent hose truly is the largest drawback of a portable unit. Which is why most product pictures tend to downplay that little detail, as a majority of photos only shows the product itself. You may notice however, that they seemingly all only have one hose. But that is a big problem.

Convert portable Air Conditioner, from single to dual hose design

Can you see the problem?

The air that is vented outside of the room needs to be replaced. It creates a negative pressure differential inside the room the unit is in, thus the vacuum draws in air from the path of least resistance. This will be in all likelyhood the place where the exhaust hose is installed – causing hot outside air to come back inside the room!

This vastly reduces the efficiency of the portable AC. But we’re not done yet – to make matters worse, the AC will inevitably use some of the room air it just expensively cooled down – and use it to dump heat into and vent outside, further reducing the efficiency.

Most portable AC units boast efficiency ratings of A and higher. However, these are just theoretical values based on the efficiency of moving thermal energy from one end of the heat exchanging cycle to the other. In real-world conditions, these systems have abysmal efficiency.

How to make portable ACs suck less

The biggest problem is clearly the negative pressure created by venting room air outside. The easiest and most obvious solution is the addition of a second hose – creating a separate loop for the hot side of the heat exchanging cycle. Outside air is sucked in, heat is dumped into it, and the air is then vented outside. Thus creating no pressure differential inside, and therefore not drawing additional hot air in.

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Single and dual hose portable ACs compared.

For reasons beyond my understanding however, there seem to be no dual hose ACs on sale anywhere in Germany. I can only conclude that this is done purely because the manufacturers don’t need to do it. The energy label rating, as stated previously, is entirely fictitious regardless of single or dual hose use. And consumers are likely already annoyed by having to install a single hose. The installation of a second hose therefore may be the straw that breaks the camel’s back.

61dLs5iDtL. AC SX569 2 1 - Greatly improve portable AC unit efficiency
The different vents on a portable AC unit

That leaves us to take matters into our own hands. It is possible, and actually fairly simple, to convert a single hose portable AC to a dual hose portable AC. First off you need to identify the vent where your AC draws in ambient room air to cool down the hot side of your AC.

I have a fairly cheap whitelabel AC I bought out of dire need at a local grocery store. It does have a lot of bang for the buck, but also has the flawed single hose design.

  • RED: This is the hot side air intake. This is where we will install the air intake hose.
  • GREEN: This is the hot side air exhaust. This is where the regular exhaust hose is installed.
  • BLUE: This is the cold side air intake, which takes the room air, where it is then cooled down and vented out the other side.

The Quick and Dirty Way

What you need:

ComponentDescriptionWhere to buy
AC air hoseThe air that draws in the outside air. It should be identical to the exhaust vent hose to reduce the strain on the motor.Amazon.de
Amazon.com
AC air hose flangeThis will allow us to attach the intake hose to the intake cover.Amazon.de
Amazon.com
Duct TapeRegular duct tape. I said this is the quick and dirty way after all.Amazon.de
Amazon.com
Window AC adapterAn adapter to fit the intake side into a smaller slot on the window. Not strictly necessary, but recommended.Amazon.de
Amazon.com
Carton or other building materialTo cover the intake vent. I’ve used carton boxes, but nearly anything will do.Be creative!
BoM
  • Cut the carton in a shape large enough to cover the intake vent. Before installing it, cut a hole about center of the cover and attach the hose adapter.
  • Proceed to attach the cover to the AC unit and seal it with duct tape.
  • Now attach the hose, once again seal it with duct tape.
  • Proceed to hang the intake vent outside the window. Make sure to keep a distance to the intake hose, to prevent an air short-circuit.
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The quick…

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… and dirty way.

It ain’t pretty, but it works! I don’t have the tools necessary to take accurate measurements, but not only has the AC now managed to cool the room down far more, the compressor now occasionally turns off as it has reached the target temperature, something it had not done before.

The Proper Way

Now, while the above may work, surely there is a more aesthetically pleasing way? Well, you’re still going to be stuck with two ugly hoses hanging out of a window, so it’s going to be a losing battle, but I’ve designed a replacement attachment for the intake vent:

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The 3D Printed adapter alternative

Because I currently lack access to my 3D printer, I was unable to print the adapter myself. The installation process is much the same.

Conclusion

Once again, where manufacturers fail, makers like us can make up the difference. With just a little bit of duct tape and carton, you can vastly improve the experience of your AC (and lower the electricity bill to boot!). I hope this helped – and if you know someone who also uses one of these abysmal AC units, tell them about this to make their misery slightly less agonising!

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