How to Make Your Wall Air Conditioner Really Cold

Having recently pared down a lot of my personal belongings, I similarly felt a need to reduce the footprint that I use as a living space. So, I moved into a much smaller apartment, with which I am very happy.

Being a smaller unit, the architects who designed my apartment rightfully spec'd it with a proportionally smaller air-conditioning unit. In this case it's a high-efficiency wall-mounted AC. It's a small thing - about 1½ x 2 ft (45 x 60 cm). And luckily it is brand new, too.

I live in a climate where the summers are hot. Really hot. While running the AC throughout the day is a must, the electric company doesn't lend a helping hand. They will gladly charge me upwards of USD $100 or more per month to keep my place cool. All in spite of the fact that my air conditioner is a "high-efficiency" unit.

Saving Money on the Electric Bill

Not wishing to throw my money down a dark hole for my electric bill any further, I set my mind to how I could raise my air conditioner's efficiency even further without causing any dangerous modifications.

How An Air Conditioner Works

When you think about what an air conditioner does for you, it basically just moves heat from one inside of your wall to the outside.

To do this, the air conditioning unit uses a compressed gas traveling through metal tubes to grab excess heat from the air inside your home. This hot gas then travels to metal tubes outside of your home, where a fan blows the heat off of the metal tubes and into the ambient air outside. The gas in the tubes then travels back into the network of tubes which come in contact with the air inside your home, and grab another batch of heat to be taken outside once again. This cycle goes on continuously while your air conditioning is running. (See the accompanying Image 4, which diagrams this process.)

This entire process requires a lot of energy, and at the end of the month it can amount to an expensive electricity bill.

With a more efficient air conditioner, I wouldn't need to run it quite as often. Therefore I could reduce my electricity consumption and save some cash at the same time.

Flaw In The Design

In looking at how my wall-mounted air-conditioner works, I see that it has one major design flaw. It discharges hot air from its outside panel into the ambient air outside my apartment (see Image 5), but much of this hot air ends up getting sucked back up by the air-conditioner's cold air intake duct (see the accompanying images). The AC uses hot air to "cool off" an already hot set of outside tubes.

It's inefficient because the air conditioner ends up having to run much longer to cool things off.

How to Reduce Energy Consumption?

In an ideal situation, only cooler air should run into the outside cold air intake duct.

So, how to do this?

After some time, my thoughts drifted to an article I had written recently about an automotive technology called a cold air intake - a device that addresses a similar problem that cars and trucks have with unwanted heat. Read the cold air intake article by clicking here.

How A Cold Air Intake Works

Basically a car or truck cold air intake system separates hot engine discharge air from the cold air a car's engine likes to inhale. By doing this, the engine runs more efficiently, and likewise delivers more power.

Upon thinking about this, I figured that my air conditioner could benefit from a cold air intake.

A Simple Air Conditioning Cold Air Intake

Before getting started, I removed the outside protective grill that keeps leaves, kids, and other outside debris from damaging the delicate external workings of the air conditioner unit.

Next I crafted my air conditioner's cold air intake from a long cardboard box.

To do this, I cut a hole at one end of the cardboard box that matched the shape and size of my air conditioner's cold air intake vent. The open end of the cardboard box points well away from the air-conditioning unit, and therefore is able to suck up relatively cool air well away from the heat that gets discharged by the air-conditioner.

What this does is completely separate cold from hot air. This results in the air-conditioning unit working much more efficiently.

After a little tweaking and trimming, the cardboard box fit perfectly over the air conditioner's cold air intake vent. When finished, I sealed up the gaps between the cold and hot sections completely with some duct tape. To make the cardboard box somewhat rainproof, I used some more duct tape to cover the box with a plastic garbage bag. So far my new cold air box has survived several rain storms.

But Does It Work?

After all this effort, it's nice to know whether the new apparatus works. It certainly does.

Using a common industrial air-conditioning thermometer, I measured my unit's cold air "before" and "after" temperature going into the house. Before installing the cold air intake box, the air came into the house at 46° Fahrenheit. After installing the box, the air came in at 42°.

While only a few degrees cooler, there was a appreciable change in how cool the air felt, and a noticeable reduction in the time it took to cool off my house.

Sources / Other Reading:

Automotive Cold Air Intake
John's Other Articles