Here’s the overall view of the unit. A high speed fan pushes the air through the perfectly sized radiator, and water flow rate is controlled by a small hand valve.

The radiator itself was horribly filthy when I first took it off, but a quick soak in some warm water and light detergent took care of it. The copper tubing inside the radiator is the exact same diameter as the copper tubing I used when I first built my original homemade air conditioner, so no need to change up the vinyl tubing.

I placed the fan fairly close to the radiator itself, and it works great. I typically put the fan on the medium or low setting, as I notice little benefit from the high speed setting other than increased noise.

The radiator was almost perfect, it only needed to be raised by a centimeter or so to align with the fan. Turns out old original Nintendo cartridges do the trick just fine. (For the record, that’s Teenage Mutant Ninja Turtles and Marble Madness. Don’t worry, I have other copies.)

Cold water is supplied from an outside garden hose. More detail can be found in the water supply section.

To calibrate the valves, the small hand valve inside is first opened wide and the garden hose opened or closed to find an appropriate upper flowrate. Then the hand valve may be used to vary the water flow or turn it off entirely.

The nice thing about this new setup is that all control is now done from inside the room. Starting and stopping the unit is far more convenient, which leads to more efficient water usage. The performance of the unit is drastically improved over the old design. Less water is needed, and the room cools quicker.

Here’s the overall view of the unit. You can see the insulated polystyrene box containing icewater and the aquarium pump, along with the fan and attached copper tubing.

Pete did a much neater job of attaching the copper tubing to the front of the fan than I did. Using copper tubing on both the front and back of the fan is a great idea, the more copper tubing, the more heat exchange possible.

Here is a view of the unit from above, allowing us to see the copper coils on both the front and back.

Here we can see the entire system on its rotating base, allowing directional cooling (most) anywhere in the room.

This picture shows Pete’s innovation, the Internal Cooler Coil (ICC) ready to be installed. The water first runs through this coil, through the ice water, and then out to the fan. Pete and I are wondering if this actually increases performance at all, but it sure looks cool.

Here we can see the aquarium pump submerged in the ice water. Pete aims to increase the power of the pump, and replace the polystyrene container with something more permanent. A small freezer with its heat vented to the outside would be ideal.

If you liked Pete’s design, check out Spencer’s heavy duty interpretation, or my final design.

A spare radiator from a 1976 Triumph Spitfire ensures great heat transfer between the water and the air. A wooden frame supports the radiator and attached fans.

Not just one, but two fans circulate air through the radiator and the room.

Two water fountain pumps are used to circulate the water between the cooler and the radiator.

Here we can see the warm water returning to the cooler. How does the whole thing perform? In Spencer’s words, very well.

Here’s the overall view of the unit. The condensation collector and flow valve are both visible. It’s a good idea to place the unit higher in the room like this, the action of the fan will circulate the hot air at the top of the room. Just make sure that your ceiling tiles aren’t flaking off abestos and you’re set.

This is the rear of the unit. You can see the copper tubing coiled along the back of the fan, attached by zipties.

The condensation collector sits below the unit. A towel catches any spare moisture not managed by the collector.

Here is a closeup of the flow valve. This is extremely useful in managing flow rate, or stopping water flow entirely. If installed on the outflow side of the system, the flow valve allows the siphon to be restarted very easily once shut off. If the system lacks a valve such as this, air will bleed back into the tubing and make it more difficult to restart the siphon.

An additional benefit of the ice water source is shown to the right. In extreme heat situations, one may sit in the ice water source for drastically improved cooling effect. Additionally, one could simply drink the beer cooling in the ice water. In heat waves, do your best to stay out of rehab.

Waste warm water is directed to a garden, no student ghettos here. Oh, how I yearn for the days of a mortgage and a house without concrete as a landscaping tool.

Several people have asked me if I have managed to quantify the performance of this system. I ran a few quick numbers – accuracy is not going to be great due to measurement error. In terms of rough numbers though, I’m pretty happy.

At a flow rate of 2 L/min (taken as the upper range of performance) inlet temperature is 16 degrees Celcius (C), and outlet temperature is 20 deg C. This corresponds roughly to 2000 BTU/h.

At a flow rate of 1 L/min (what I use for a hour before bed to cool the room off) inlet temperature is 16 deg C and outlet temperature is 21 deg C. This corresponds roughly to 1200 BTU/h.

At a flow rate of 0.5 L/min (what I would use for “maintenance” after cooling the room off if it’s a hot night) inlet temperature is 16 deg C and outlet temperature is 23 deg C. This corresponds roughly to 800
BTU/h.

In terms of BTU/$, I can’t complain. If I’ve made any errors in my calculations, feel free to chastise me.

UPDATE: My school requires me to write a “work report” for every term of outside work experience during the coop program. I felt the only logical choice was to do it on the infamous homemade air conditioner. Hopefully referencing yourself in your work report (PDF) is looked upon kindly by admin…

The system is fed from a tap on the side of the house. The hose is ancient so the connection is a bit leaky, but a bit of tape stopped that quickly. I added on some pipe insulation (~$1.50) around the garden hose to make sure the only thing warming up the cold water is my stupidly hot room.

The water supply in Waterloo is typically from groundwater sources, so the garden hose tends to be quite cold regardless of season.

The hose insulation ends under my window. The remaining length of garden hose is coiled and wrapped with towels to insulate.

The garden hose is then connected to the vinyl tubing with duct tape, of course. It then leads through a small hole in my screen towards the fan. I must congratulate my landlord on the exceptional job he does on basic maintenance, such as exterior paint touchups.

The tubing feeding the system cold water can be seen at the bottom of the window. Water circulates through the heat exchanger, and the warm waste water is pumped up towards the roof.

Another small hole was cut in the screen for the warm waste water line. It then passes an old bird’s nest (a necessary accessory for any student ghetto) and leads to the roof.

The warm waste water is pumped onto this garish prefabricated roof, which covers part of the backyard. Hopefully, a side effect of this is a slight temperature drop on the roof due to evaporating waste water. This may have a minor effect on the outside temperature near the room.

You can also pump the waste water into your eavestroughs. This makes sure you’ll be draining to a location that won’t flood your basement.

The water eventually drains off the roof. If you’re of the Zen persuasion, the gentle sound of running water will lull you off gently to sleep. If you aren’t, it may drive you absolutely mad until you realise that the sound of the fan drowns it out anyways.

The water drains to the same garbage pail, which can be dumped on the lawn or used for watering plants, if I had any.

Strips of tinfoil were first used. You can see some of the copper coiled along the front, from an earlier attempt to improve the heat exchanger. This wins in the cost department, but ultimately the choice was made to discontinue the use of foil as it had the annoying habit of coming undone and buzzing like mad during the night.

The decision was made to completely revamp the copper coils, and install the entire length of tubing on the front of the fan. You can see the recoiling in progress, I did a bit neater job this time (but not by much).

Here’s the completed copper coil on the front of the fan. Cold water is fed from the centre to the outside. Again, I’m unclear as to what configuration if any (cold from the inside, cold from the outside) would lead to superior performance.

I decided to use wire to create a mesh on the front of the coils. (18 gauge wire, Radio Shack, ~$5 – I’m up to 30 bucks now!) This would increase surface area, intercoil heat transfer, and turbulence near the coils, hopefully increasing performance.

I first attempted to solder the wire to the tubing, a stupid attempt as the entire system is designed to efficiently transfer away heat. After several minutes of terrible cold joints, another approach was required.

I ended up weaving the wire from the centre to the edges, and back in. Approximately 10-12 passes were used per quarter section of fan.

Here’s a shot of the completed upper left quarter.

Weaving the wire is an unbelievably frustrating experience at times. The copper tubing usually has a slight gap between the white wire mesh on the front of the fan that the wire can pass through, but at other spots the wire will catch and start to unravel. It helps to have the proper tools (needle nose pliers, beer) to stay relatively stress-free. In this shot I’m halfway through weaving the lower right quarter.

Just be patient and you’ll be fine.

Here’s the fan as it stands right now. Saturday went from evening to night, and that means I need to go somewhere with cold pints and hot women. I’ll complete the remaining quarters tomorrow when I have a bit more time and patience.

Preliminary tests are very satisfactory. The cooling rate has increased, and the room will get a bit colder as well. This will help in extremely hot situations, where heat would leak into the room as fast or faster than the system could remove it.

Materials:

Salvage from around the house a:

• large fan
• garbage can

Grab from Home Depot:

• 25 feet of 1/4 inch outer diameter (OD) copper tubing (~ $14)
• 20 feet of 1/4 inch inner diameter (ID) vinyl tubing (~ $6)
• a package of zipties (~ $3)
• 2 small hose clamps (~ $1)

Construction

Here’s the basic setup. The garbage can is filled with ice water, which is then fed by gravity (a siphon) through the copper tubing coiled along the back of the fan. The hot air passing through the tubing warms the cold water, cooling the air. Waste warm water is then pumped outside.

The system will cool an average room to a comfortable level in approximately 15-20 minutes. Depending on flow rate, a full bucket of water will last approximately 1-3 hours. I use a single bucket before bed on hot nights, which lets me get to sleep. Once the water runs out, the house has cooled off enough that the fan alone provides sufficient cooling.

It doesn’t rip quite as hard as central air, but for less than $25 CAD I’m not complaining. (and, btw, that’s my girlfriend’s makeup mirror, not mine)

The main factor affecting the performance is the temperature of incoming water. Cool water will work, but ice water will result in a cooler room, quicker.

Add salt to the water if you’re adding a large volume of ice, as this will drop the freezing point of the water and increase the cooling effect of the fan.

You can attach the tubing to the front of the fan as well. This will increase performance, just make sure that your fan can handle the additional torque of tubing full of water attached to the front.

Here’s what the fan looks like from the back. The biggest issue in construction was uncoiling 25 feet of copper tubing in a 15 by 20 room. Just be patient and don’t attempt to bend the copper too severly, it’ll fold over on itself and you’ve effectively chopped your nice copper tubing in two.

When coiling the copper into a spiral on the back of the fan, I started in the middle and put zipties every 15-30 cm (6-12 inches). Use your discretion, you want to preserve the spiral shape and keep the tubing as close to the metal mesh as you can. If you’re a bit crazy, sand the paint off the back to improve heat transfer from the metal mesh.

It doesn’t really matter how it looks as long as it’s reasonably spaced out and consistent. A hint for construction: prebend your zipties into a J shape. Then you can hook them easily in and back out of the metal mesh on the back of the fan. I’d suggest cutting off any extra plastic once you’ve got them on.

Some have suggested using an old car radiator attached to the front of the fan instead of coiled copper tubing. Cost prevented me from trying this, but as long as the head loss from the radiator is low enough to allow the siphon (or pump) to operate, this should increase the performance (better heat exchange). You’ll likely have to construct a frame to hold the radiator in front of the fan.

If you look closely, you can see the condensation from the incoming icewater, but no condensation on the tubing leading out. This is perfect, as it means that heat is being transferred from the room to the water.

Once you’ve got the copper tubing coiled, the rest is easy. Cut your vinyl tubing into 2 pieces, with one about twice the length of the other (one piece 6-7 feet, other piece 13-14 feet).

Attach the shorter piece to the incoming side of the copper tubing. It should slide relatively easily over the copper, but be snug. Attach the hose clamp and tighten. Following a similar procedure, attach the longer piece to the outgoing side of the copper tubing. (I don’t believe it really matters whether you feed cold water from the inside or the outside. It’s up to you to run some numbers.)

Submerge the shorter end of the vinyl tubing in the garbage can (washed and clean). I suggest weighing down the end of the tube, to avoid it drawing in air and stopping the system. I used twist-ties to attach a thin rock to the end. If you have fishing weights, I would suggest using those. Then again, if you have enough stuff for fishing weights to be lying around you can probably afford a real air conditioner.

Next, hang the longer tubing out your window. For the gravity pump to work, the end of the tubing must be below the water level of your garbage can, plus an allowance for head loss in the pipe. Just to be safe, get it as low as you can. I’d suggest arranging it so the waste water will feed into a garden, but student ghettos don’t have gardens so in this picture it’s being fed into a drain by the basement.

I had to poke a small hole in my screen for this to work.

To get the system started, make sure the vinyl tubing in the ice water is completely submerged. Then, bring the waste water tubing as low as you can and start sucking on the tube. If you’ve ever siphoned gas you know the drill.

Basically, suck as much as you can. Then plug the end of the tubing with you thumb, and repeat. You’re done when you start tasting water. Just let go, and it should continue to flow normally.

I’ve also hooked this up to a garden hose as the cold water feed. Check out the improved water supply.

Errata:

• A closed circuit version of this is entirely possible. An example can be seen here.
• I would also suggest constructing a geothermal heat pump. Dig a deep hole near the window, the soil at this depth will be quite cool. Bury a coil of copper tubing spaced well through the soil, this will act as your heat sink. Pumping water from the fan coil to the underground coil and back will exchange heat from the warm room to the cold soil. I’d love to implement this, but my landlord may not take well to large holes in his backyard.
• I realise small air conditioners are quite cheap. But then you don’t get to build anything!

It was the summer of 2005, and a heat wave was sweeping across Ontario. At the time I was working on my engineering degree at the University of Waterloo, and tuition was just a little steep. As such, I lived in a cheap student house with no air conditioning. Fueled by a combination of too many engineering courses, too little money, and an overarching desire to not die of heatstroke before I graduated, I made my own air conditioner.

I put a few pictures of it on the internet, and then things got a little crazy thanks to Slashdot. I was featured on CTV’s Canada AM, had stories in The Kitchener-Waterloo Record and a few other newspapers, and was interviewed by a few radio stations including CBC Radio and NPR.

When you get down to it, it’s a basic heat exchanger, using water as the medium. You’ll probably need to fiddle a bit with the dimensions of the supplies based on your resources and preferences.

I’ve migrated this site a few times – first from the University of Waterloo servers, with their ever-patient admins, and then from a separate micro-site on this blog. This is my personal “blast from the past” that I’ve preserved for the sake of memory – it made for a rather entertaining summer!

Original Air Conditioner Concept

This is the first version of the air conditioner I made. Click on the pictures for more details.

Geoff’s Original Homemade Air Conditioner

Heat Exchanger Improvements

Water Supply Improvements

Technical Notes

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Final Design

This is the final design I settled on after fiddling for a while.

The Black Beauty

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Other Designs

These are some homemade air conditioners other people from around the world have made.

Pete’s Homemade Air Conditioner

Anonymous’ Homemade Air Conditioner

Spencer’s Homemade Air Conditioner

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