DIY Air Conditioner

Over a year ago I was introduced to the concept of building your own air conditioner by a friend of mine. Since then, I've wanted to make it for those few, but very miserable Seattle summer nights when it doesn't cool off. Finally, I was able to purchase the parts and piece it together.

It was recommended that I post the instructions on how I did it, so that's what I'm doing. Before I begin, I have to give credit to two other sites that I based my construction on:
http://www.instructables.com/id/Hollis-homemade-AC/
http://www.instructables.com/id/Homemade-air-conditioner/

Ok, now on to the instructions...

Materials

- Fan (I chose to use a box fan, but you can use any fan)
- Styrofoam cooler (you can use plastic, by stryofoam is easier)
- Copper Tubing (1/4" outer diameter, 20' long)
- Clear Vinyl Tubing (3/8" outer diameter, 1/4" inner diameter) (I only used 1', but couldn't buy it in anything smaller than 20')
- Tube/hose clamps (1/4" - 5/8" clamping range)- Small Fountain Pump (mine is 130 gallons per hour)
- Tape Measure
- Box Cutter
- Zip ties
- Screw Driver (philips & flat head)
- Sharpie

The Fan


1. Take your copper tubing and begin to uncoil it on your fan. Leave a length of tubing descending below the bottom of the fan (this will go into the cooler through the lid). The exact length to leave below your fan will depend on the cooler you purchase.

2. Take your zip ties and fasten the copper tubing to the grill of the fan to hold the tubing in place. 

Note: the copper tubing is fairly ridged and will hold it's shape relatively well, but it can also bend easily, so be careful not to put any kinks in the tubing or water won't flow through it!

3. Continue to coil the copper tubing around the outside of the fan, fastening with zip ties as you go. Again, be careful as you bend the tubing so as not to kink it and slow/prevent water flow.

Tip: before deciding where to place your tubing, turn on the fan and feel where the air blows through and where there are "dead spots" with now air blowing. Only place the tubing over areas that has air blowing over it! I didn't think about this until after I attached all my tubing...

4. Continue to wrap the tubing around the front of the fan, attaching with zip ties as you go, coiling inward towards the center of the fan. (I feel kinda' silly mentioning this step, as it seems pretty intuitive)

5. As you get closer to the center, you might find it easier to coil the remaining copper tubing upward. Otherwise the tubing gets caught on itself as you continue inwards!

6. Once you get to the center, you'll reach a point where you can't really coil the tubing any further without risking kinking it (it'll also be in an area where no air blows).

Once you reach this part, take the remaining tubing and bend it downward past the bottom of the fan to mirror the start of the tube.

7. I left a gap between the originally coiled copper tubing and the last bit of tubing running to the bottom of the fan. While this probably doesn't make a huge difference, I made sure the tubing didn't touch so heat does't get transferred between the different parts of the tubing (copper is a good conductor of heat, so if they don't touch, they won't conduct).

8. Now cut the extra ends of the zip ties off so they aren't sticking out. I recommend pushing the ends down into the fan (left) and not pointing out away from the fan (right) to prevent getting scratched/cut on the ends of the remaining zip ties.

9. Next, use sand paper to dull down the edges of the copper tubing (the tubing I purchased came with pastic caps on the ends that I left on until after coiling. You could also do the sanding before coiling). Because I was doing this in my family room on carpet, I sanded over a phone book (I didn't have any newspaper).

Measuring 
May I recommend that you have another person with you while you do the rest of this? I did it by myself, but it would have been MUCH easier with 2 extra hands!

10. Measure the width of your fan and the width of your cooler lid. I'm visual, so I had to draw myself a diagram. The fan was 21" wide and my lid was only 17" wide. This means when I measured the location of the tubes coming off the bottom of the fan, I had to take that extra 2" per side into account.

11. On the right side of the fan, the copper tube is about 5 1/4".

12. Now I place the tape measure up to the lid of the cooler, being sure to line up the right side of the lid with the 2" mark to account for the wider fan, then I used a sharpie to make a dot on the lid where the copper tube should be.

13. Repeat the same process for the left side of the fan/lid. (Had I been thinking in the beginning, I would have centered the tubes in the lid as I coiled the tubing on the fan. I didn't, and it's not super important)

14. I did one additional measurement for the depth of the fan, since the fan has to sit on top of the lid and the tubes come out the front of the fan. I then took that measurement and wrote an additional dot on the lid for the exact location of the tube (the X to the right in the picture).

15. Now use a philips head screwdriver to poke a hole into the lid of the styrofoam cooler in the positions you made your final marks (if you are using a plastic cooler, you'll have to use a drill or something).

16. Take the lid and pass the copper tubes through the holes you made. If you measured correctly, it should fit (because the copper is flexible, there is some give in the tubing to fit even if your measurements aren't exact). I took the extra tubing and looped it around so it wouldn't run into the bottom of the ice chest. You could also cut it off with a hacksaw or something.

The Pump

17. Take the pump and place it in the cooler with the electrical cable draping over one side.

18. Use a box cutter to cut a notch in the side of the cooler so the lid will sit flat on the top of the cooler.

19. Next, figure out how much vinyl tubing you will need to get from the pump at the bottom of the cooler to the copper tubing coming from the fan. Measure how far from the top of the cooler (the place on the lid that comes in contact w/ the cooler top) to the bottom of the tubing. Then measure the distance from the top of the pump connector to the top of the cooler. The difference should be the length of tuber you need. I drew another amazing (not at all to scale) diagram to help me figure out how much tubing I would need. Note: you only need to attach one end of the tubing to the pump. The other end will simply let the water back into the cooler.

 20. I added an additional 6" to the 4" I needed to help give some flexibility in the cooler and hopefully to prevent the tubing from knocking the pump over. Use your tape measure and mark on the tubing with a sharpie where to cut.

21. Use a box cutter to cut the vinyl tubing at the mark.

22. Take one end of the vinyl tubing and place it over the copper tube coming out of the bottom of the fan (through the lid). Take one of the tube clamps and place it over both tubes. This will seal the connection between the two tubes and prevent water from leaking at this junction. Use a flathead screwdriver to tighten the clamp around the two tubes.

23. Then take the other end of the vinyl tube and attach it to your pump. Each pump is different. Mine came with a connector that just barely lets the vinyl tube fit around it. The connection was tight enough that I didn't think an additional tube clamp was necessary. Depending on your pump connection, you might want an additional tube clamp at this junction as well.

Putting it All Together

24. Fill the cooler with cold water; the colder the better job your AC will do of cooling the room! Be sure to leave room in the cooler for the displaced water when you add the pump and ice. You don't want water overflowing out of your cooler!

25. I freeze ziploc bags with water in them so I can reuse them after they're melted. You can also use old water bottles as well. You could even use those "blue ice" containers used in lunch boxes and coolers. Its up to you, but I figure it's easier to have something you can re-use (and it uses less water that way!).

26. Now put the pump into the cooler with the lid and fan and...Viola! You've got yourself an air conditioner! (this is really hard to do yourself, so get someone to help you if you can)

I have not had a chance to really test mine yet, but it looks cool, right? :)

The Science


For those of you who are interested, here's the basics behind why this should work. As I mentioned before, copper is a good conductor. Usually people think about electricity when talking about conductors (or trains or orchestras...but now I'm really off track), but heat (thermal energy) is also conducted between objects when they touch each other. For some visuals, check out this page.

Anyway, copper is a good conductor, which means it can transfer thermal energy (heat) pretty well and quickly. So in essence, when we're pumping the cold water through the copper tube, we're using the copper's conductivity to transfer heat FROM the air and INTO the water (via the copper). We're pulling heat out of the air!

That's great, but what about the fan? Well, the fan adds another type of thermal energy transfer: convection. Convection is transferring thermal energy (heat) by moving some sort of fluid, in this case, air. By moving the air across the copper tubing, we are allowing more air to come in contact with the copper, thus also allowing more heat to be pulled from the air as a whole. Convection is the same thing that makes you feel colder when its windy than when it's not (most of the time), as well as one of the reasons we sweat to cool off.

Basically, the fan forces convection, which allows more air to conduct it's heat into the copper tubing and into the water, therefore cooling the air and making it much more comfortable to sleep at night! : )

Disclaimer: I am over simplifying the science behind how this DIY: AC works. The whole process is more complicated and involves more things, but this is enough to understand the basics.