Geoff’s Original Homemade Air Conditioner

Note that this was my very first attempt at homemade air conditioning, preserved for posterity -
if you’re planning on building your own, take a look at my main page or my final design, the Black Beauty.

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

01_fanbucket

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.

02_ice

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.

03_fanback

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.

04_fandetail

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.

05_window

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.

06_exit

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!
Homemade Air Conditioning Plans and Pictures
Original Design
Geoff’s Homemade Air Conditioner
Heat Exchanger Improvements
Water Supply Improvements
Technical Notes
Other Designs
Pete’s Homemade Air Conditioner
Anonymous’ Homemade Air Conditioner
Spencer’s Homemade Air Conditioner
Final Design
The Black Beauty

58 thoughts on “Geoff’s Original Homemade Air Conditioner”

  1. I’m 26 from the Philippines, Thanks a lot for your brilliant tutorial! Oh man this will really help me specially during hot summer days in my room. Cheers! ;)

  2. Hey i built one with the copper tube. I have a few problems.

    1. The water condenses & starts dripping off the copper tube.
    2. Wont cool musch.

    & can someone pls tell me which is better. Using copper tubes or a radiator from a car.

    1. Hi Nilushan,

      The water condensing off the tubes is a result of high humidity in your room. As the air cools, the water has to go somewhere. Commercial air conditioners will collect this and release it outside, you could try to construct something similar.

      The cooling rate is a function of the effectiveness of your radiator, and the volume and temperature of your cooling fluid. To increase cooling, you can try (in order of likely effectiveness)

      1. Improving your radiator.
      2. Decreasing the temperature of the water.
      3. Increasing water flow.

      Using a radiator will provide much better cooling – as the copper pipes are effectively a homemade radiator with less surface area and more resistance to air flow.

      1. Ok, now i understand the concept abit.

        But should i put the copper tubing at the front or the back or both ? which is better choice ?

        What if i juz circulate the water without the ice, usually it will produce what temperature?

        If with ice, whats the standard temperature it can reach?

  3. Why can’t you make the system circular and just have the water go round and round, entering the ice and cooling then leaving to the fan and then back to the ice for cooling? It seems it would be much simpler. I want to make one of these but for a vehicle turn camper.

  4. Thanks for the reply!

    So if you had a closed and ‘open’ design with equal specs, how much less would say the ‘closed circuit’ performs percentage wise?

    1. They’ll perform similarly to start, but the closed circuit systems can only cool to the point where all the ice/cold water in the reservoir is used up and the system reaches equilibrium with the room. The open circuit systems will cool as long as cold water is flowing through them.

  5. hey,
    I have an old refrigerator that is still working. Can i remove the parts of it and build an AC to cool my room? If so what are the parts i need to remove?
    And will it actually cool my room?

    1. You could try to hack together some sort of contraption where the heat from the condensor is vented outside and the room is cooled by the evaporator coils, but that seems to be asking for high-pressure coolant to be sprayed all over the place unless you have training in that sort of thing.

      I would suggest having the coolant drained and using the coils for parts and experiments. I did something similar with the condensor from an old freeze drying machine that you can see here.

  6. hello,
    geoff’s ur ac …..better then a table fan……but u used a fountain pump to run water through a copper tube …..my suggestion is some what different….plz try this also……in stud of fountain pump use vacume pump which is connected to copper tube which is placed inside the ice cubes copper tube is made spring like structure and pump will trap hot atm air and when it passes through ice placed copper tube then air becomes cool and so when it passes through fan tube it will be cool air plz try this also becoz if have a bugget problem….try and tell me result….100% sure it will work…..plz

  7. Wow Geoff this is amazing idea, may be you can patenting that to make some cash :) this is one of the best ideas that i saw in the last time. Respect for your creativeness

  8. hello geoff,

    I build this the other day, i put the copper tubing infront but many condensation occcur but less cool or only 1 deggre less only…the water is much colder because i put many block of ice…are there any solutions for this geoff? thanks..

    1. I would suspect your heat exchanger does not remove heat at a high enough rate to offset the degree to which your room is being heated by solar or other sources. Copper tubing was my first attempt and isn’t nearly as efficient as a radiator like this which will work much, much better.

        1. Hi Evan – Nope, there’s not a huge difference in performance. The biggest increase in performance comes from using a proper heat exchanger instead of copper tubing.

  9. Hi Its great invention i’m very poor person so i also can have Air Condition NOw thank you very much to you

  10. Hiya, I love the idea but decided to try just a little something different. Instead of copper coil around the outside of a fan I went to AutoZone and got a $17.99 heater core, fits an 84 Chevy C10 pickup truck. Sure beats the price of copper tubing at Lowes or Home Depot. They prob have some for cheaper but after looking up every car I could think of this price was reasonable and I jumped on it. The in and outlet hose is for 5/8 tube and that fits my pump perfectly. I have a 12 inch industrial fan that the heater core sits perfectly in front of. So far so good but sure glad I ran across this idea, it has helped a GREAT DEAL

    1. Hey Bradford, good to hear it worked out for you. I strongly recommend this approach – a heater core is cheap and is designed for great heat transfer!

  11. Thanks Geoff, without your original idea the heater core thing would have never hit me so I thank you for coming up with the idea. I”m a cheap kinda guy and sure wish I had this idea a few years back while I was in college. Looking at your pricelist I sure wish copper was back to being that cheap. Again, thanks for sharing you idea…..

  12. Great idea — I used it to cool my home office room.
    The only real problem I ran into was using a 15 gallon trash can, it’s only lasting 45-60 minutes so it requires constant attention.

    I designed a way to improve the design and create a closed system and then saw that Pete did the same thing. (Using a ice chest cooler and water pump to circulate water). However the problem is it then loses it’s cheap appeal — while its still in-expensive compared to a window AC unit, for the price of the materials ($100-115) you can get a small, portable swamp cooler which will likely cool much better and can be easily moved from room to room.

    One ‘innovation’ I did come up with though was in the ice water =P I took about 50 pear-size water balloons, filled them with water, froze them and used them as giant ice cubes — they’re also reusable provided you don’t toss them at your friends or otherwise pop them.

    Nice engineering trick Geoff! :)

    1. Hi jagdeep – I haven’t tried it myself, but I don’t see why not – just be careful to keep everything contained and you should be good.

  13. Geoff,

    What up man. Thanks so much for building this. My wife, 1 year old, and I just moved to Morocco and it’s hotter than a hockey stick in the devil’s hand! And of course, no a/c. So, I’m working on it…I’ll let you know how it goes.

    1. Hi Billy – The most efficient way to construct this would be to use a radiator/heater core or similar. Copper tubing works, but only transfers a fraction of the heat. If you look around at surplus stores or similar you can find a radiator for less than the price of copper tubing.

  14. If I were to try and use an old fridge as an AC I would put the fridge outside and use some flexible insulated ductwork to circulate air in/out of the fridge. What I would say is that if you hit some yard sales or craigslist you can pick up a window unit for about as much as the junk you are going to use trying to make one of these contraptions

  15. You do know the heat generated by your fridge to make the ice is the same as the cool you get out of the ice right?

    1. Of course – which is why when I used this I slept in my bedroom, not in the kitchen next to the fridge. This is a heat pump, and where you pump heat from and where you pump it to are up to you!

    1. Hriday,

      It will work in high temp areas provided the ice-water is monitored and the room has good insulation. A 44°C change in temperature will dramatically increase the rate at which the ice melts while sitting there. So using the cooler would be better than the trash-can…

      However, in 45°C environments, you may just want to use a swamp cooler and sit in-front of that (as the person with the 4 previous posts points out). Issues with swamp coolers, or bowls of ice in-front of the fan, is that it increases humidity in the room. If you do the fan and ice bowl trick, you want to be diligent about the keeping the floor dry to prevent water damage/inadvertent electrical damage.

    1. Brain – Well, otherwise it falls off! The zip ties just keep the tubing close to the airflow created by the fan and help with heat transfer.

  16. replace the bucket with a mini fridge and another copper coil and you could siphon water out of a bucket and you wouldnt need ice, i guess you could also just leave the fridge open. but that warms up all your beer. :)

    1. stupid!opening the fridge wont do anything as it will only create equilibrium, heat absorbed by evaporators will be brought to the condenser and the heat from the condenser will absorbed by the ambient atmosphere.

  17. What do you think about sending the water back into the system and increasing the amount of ice that you use to cool the warmer water returning from the fan? Could this work…

  18. I guess the we are not thinking of an air conditioner as the air conditioner with compressor. here we are talking of bringing the temp of the room by creating cool air through ice water and fan this system is normally called desert cooler where water fall from the side of a box and the fan throw the cooler air. but it work in very little humidity. when the humidity goes up u cannot even sit in the room. so one should think of creating dry cool air through this system. I have a desert cooler and an compressor air conditioner. lets think and work on cooler dry air. this is the key to this innovation.

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