Things You'll Need
Basic tool set
2-by-4 inch boards
Foam insulation sheets
¼ inch oak plywood
Although these instructions can be modified to work with AC power, using a DC power supply is much more energy efficient. It is also easy to convert the unit to solar power if it is a DC setup (see Resources below).
As the cost of new kitchen appliances continues to go through the roof, and even used models rise in price, the idea of making a refrigerator on your own increasingly becomes an attractive proposition. Although this process is more complicated than just buying a new refrigerator, it is cheaper and can be more energy efficient. If you reuse parts from old refrigerators when you build the new one, you can also keep reusable waste out of the landfill.
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Check secondhand stores, junk shops and the classified ads section of your local newspaper to find a nonworking refrigerator you can use for parts. The working condition is not important because you will be using your own mechanics. It is also OK if the outside is beat up because you only want to salvage the inside storage compartment, which is well insulated with professionally molded shelves.
Remove the doors from the refrigerator so that you can remove all of the existing air conditioning components. With the doors removed, locate the wire that activates the door light and separate it from the others so that it can be reused. Remove all other wires, fans and mechanical components. These components include the compressor, the evaporator and any dehumidifiers. Strip all of these items out of the junk refrigerator.
Remove the freezer from the refrigerator. Using a chest freezer costs less and provides you with more freezer space, and it is just not practical to have a freezer on a homemade refrigerator. Use chalk to draw a line all the way around the refrigerator, just above where the storage compartment is located. Cut around this line with a circular saw to completely remove the freezer compartment. Cut through the outer skin, the insulation and the inside surface.
Build a platform frame for your refrigerator to sit on. Use 2-by-4 inch studs to build a platform with the same surface area as the bottom of your refrigerator and raise the bottom of the refrigerator about 12 inches off the floor. This makes the refrigerator a more comfortable height, and provides additional storage space down below. Once the frame has been constructed, place two sheets of foam insulation on top to help prevent cool air from leaking through the bottom of your refrigerator.
Secure sheets of foam insulation on all sides of the storage box. Use spray adhesive or a hot glue gun to place sheets of foam insulation on all sides of the storage box, including the top and the door. Be certain to reclaim the wire for the door light and run it through the insulation. You will connect this to the power supply later. Your storage box is now ready to be transformed into a refrigeration unit.
Acquire the mechanical parts needed to refrigerate the air inside your storage box. The basic components that you need are a compressor, an evaporator and some type of thermostat control. In most cases, the best compressor is the Danfoss BD-50. There are a number of DC powered refrigeration kits designed for boats that use this compressor. You can order a "Super Cold Machine" kit or similar starter kit from R Parts Refrigeration Parts Solution or another marine supply store (see Resources below).
Find a place to set up the condensing unit for your refrigerator. The unit should be placed in a well-ventilated area. If at all possible, it should be located away from the refrigerator. If you have a basement below the refrigerator, you can run a wire through a hole in the floor and mount the condensing unit in the rafters of the basement.
Install the evaporator and thermostat inside the storage compartment. Use a 1 1/2-inch drill bit to drill a hole from the inside of the storage box all the way through the insulating foam you installed on the outside of the box. Somewhere near the upper right corner or upper left corner is ideal. Push the refrigerant tube into the hole from the back of the refrigerator, and attach the evaporator tube per the instructions provided by the manufacturer. This is usually done by sliding the tube over the port on the evaporator and tightening with a screw clamp. Also install the thermostat by mounting it on the evaporator and plugging it into the thermostat plug on the evaporator unit. When finished, seal the hole with putty.
Connect the condensing unit to the evaporator. The tube that was connected to the evaporator in the previous step should be long enough to reach your condensing unit. Run this tube to the unit and connect it according to the instructions provided by the manufacturer. This is almost always done by sliding the tube over a receiving port, and then tightening a screw clamp over the tube to secure it in place.
Connect the power supply. The kit that contains your evaporator and other components will also have a fuse power supply. This power supply connects your condenser, evaporator, thermostat and door light all together into a DC power unit that uses either 12 volts or 24 volts of electricity. The power supply is then connected to a standard car battery, which can be manually charged with a battery charger, or you can set it up to be automatically recharged using solar power (see Resources below).
Finish off the refrigerator with a wood veneer. The refrigerator will be quite functional even if you leave it with just the foam insulation showing, but it will have a better appearance if you put a veneer face on it. Use 1/4-inch oak plywood to give the exterior of your refrigerator an attractive appearance. Affix the plywood sheets to the outside of the refrigerator using a construction adhesive such as liquid nails. You may wish to stain or varnish the plywood before installing it.