Refrigeration systems generally include five components: a compressor (essentially a pump), heat exchanger pipes outside the unit (the condenser), an expansion valve, heat exchanger pipes inside the box with your food (the evaporator), and a nontoxic fluorinated-ethane chemical called the refrigerant. A thermostat controls the system.

Inside this closed system the refrigerant gets converted from a gas to a liquid and back again to a gas, and while undergoing this change of state it releases and absorbs heat. The process starts with the compressor pressurizing the refrigerant. The hot high-pressure gas travels through a set of serpentine or coiled copper condenser tubes where it condenses into liquid form and releases its heat (the latent heat of condensation) into the environment, aided in this cooling by a fan, a seawater cooling system for tropical climate, or both air and water cooling (in larger systems like the SuperColdMachine).

Icebox conversion systems use a compressor like the ColdMachine Compressor, plus an evaporator and other miscellaneous parts.

Squirting through a small orifice called an expansion valve into the low-pressure side of the system, the refrigerant morphs once more into a gas, and absorbs heat while changing state. Traveling through another coil of copper or aluminum tubing inside the refrigerated compartment, the expanding chemical sucks heat from the large surface area of the evaporator. Like the liquid propane canister on your barbecue, the refrigerant gets super cold as it becomes a gas and, miracle of miracles, chills your Budweiser, quart of milk or bottle of chardonnay.

The vacuum from the compressor sucks the cold gas back around, and the cycle repeats as long as the compressor is running. The refrigerator box heats up (at a rate depending on the size of the box, the efficiency of the insulation, and the ambient temperature) and compressor cycles on, cooling it down, running typically about 20 to 30 minutes of every hour. This is called the duty cycle.