How Electric Refrigerators Work

A modern, frost-free electric refrigerator preserves food using two different cycles: a cooling cycle and a defrost cycle. These two cycles work in tandem to maintain a refrigerator temperature that is neither too hot nor too cold. The following is a quick guide to what occurs during each process.

The electric refrigerator cooling cycle

The cooling cycle of an electric refrigerator uses chemical changes in a refrigerant to extract and dissipate heat from the fridge. A refrigerant is a substance that evaporates at a low temperature, absorbing heat in the process.

A thermostat controls the cooling cycle in electric refrigerators. When this "cold control" senses too much warmth, it cycles on the compressor, which compresses the refrigerant. This increased pressure causes the refrigerant to heat up. Now a hot vapor, the refrigerant passes through condenser coils, which expel the heat outside the fridge.

Now a liquid, the refrigerant passes through an expansion valve into a low-pressure zone, where it evaporates, cooling the electric refrigerator compartments by drawing warm air to the evaporator coils (heat always travels from warm areas to cold areas). The refrigerant absorbs this heat before cycling back into the compressor.

The electric refrigerator defrost cycle

Were an electric refrigerator's cooling cycle to run continuously, frost would begin to build up on the evaporator coils, preventing proper heat transference to the refrigerant. It sounds contradictory, but a frost buildup in the freezer results in a warm refrigerator.

The automatic defrost cycle prevents this from happening. When the defrost timer signals it's time, an electric refrigerator goes into defrost mode. A defrost heater comes on and melts any frost that has accumulated on the evaporator coils. The water created by melting frost flows through a drain tube and into a pan under the electric refrigerator, where it evaporates in response to the compressor's warmth.

The defrost heater doesn't run continuously during the defrost cycle. A defrost thermostat monitors the temperature, and cycles the defrost heater off to prevent overheating. Once the defrost control advances back to cooling mode, the compressor and fans kick in again as power is redirected to the cooling system.

In addition to freezer and refrigerator compartments, most electric refrigerators have separate drawers or areas for meats or fruits/vegetables. These dedicated compartments are designed to maintain different temperatures. Some electric refrigerators also have vegetable crispers with separate temperature and humidity controls.