Refrigerator Basics - How They Work

Refrigerators have separate systems that are responsible for different features. However, not all refrigerators have all systems.

Automatic defrost

Today, all but the smaller, apartment-sized refrigerators are self-defrosting. Frost continues to accumulate inside the refrigerator, but it melts automatically. The self-defrosting system has three functional components:

  1. Defrost timer - The timer is like a clock. It continually advances, 24 hours a day. Every 6 to 8 hours, the timer turns off the cooling system of the refrigerator and turns on the defrost heater.
  2. Defrost heater - The defrost heater is similar to the burners on an electric stove. It's located just beneath the cooling coils, which are concealed behind a panel in the freezer compartment. The heater gets hot. And, because it's close to the cooling coils, any ice or frost build-up melts. As the frost and ice melt, the resulting water drips into a trough. The trough is connected to a tube that drains the water into a shallow pan at the bottom of the refrigerator. The water is then evaporated by a fan that blows warm air from the compressor motor over the pan and out the front of the refrigerator.
  3. Defrost thermostat - The process ends after either the amount of time specified on the timer or when the defrost thermostat near the cooling coils senses that the heat near the coils has reached a specific temperature.


You'll more quickly understand refrigerator cooling systems if you think of their action as "removing heat from the air in the refrigerator" rather than "cooling the air in the refrigerator." All residential refrigerators work on the same principal for cooling. They all have:

  1. A Compressor - the motor or engine of the cooling system. The compressor runs whenever the thermostat calls for cooling.
  2. A Condenser - is a series of tubes with fins attached to them, similar to a radiator. It's always somewhere on the outside of the refrigerator, near the cooling fan to draw room air over the fins and dissipate heat from the tubes or fins.
  3. A Metering Device (Capillary Tube) - a tiny copper tube attached from the end of the condenser to the beginning of the evaporator. The capillary tube controls the pressure and flow of the refrigerant as it enters the evaporator.
  4. An Evaporator - The evaporator is always located on the inside of the refrigerator, usually inside the freezer compartment. It also resembles a radiator. When the liquid refrigerant comes out of the small capillary tube, it’s injected into the larger tubes of the evaporator causing a pressure drop. This pressure drop allows the refrigerant to expand back into a gaseous state. This change of state from liquid to gas absorbs heat. The gaseous refrigerant travels through the evaporator tubes, back out of the refrigerator and down to the compressor to begin the circulation process again.

Temperature control

All refrigerators have a thermostat which maintains the proper temperature. When the refrigerator reaches the set temperature, the thermostat interrupts the electricity flow to the compressor, which stops cooling.


Refrigerators with internal lighting normally have only one functional component--the switch--which is usually a white push-button mounted inside the refrigerator near the door. When the refrigerator door closes, the door pushes the switch to turn the light off. When the door opens, the button automatically pops back out to turn on the light. The light bulb itself is usually a standard appliance bulb.

Ice maker

The ice maker is a small appliance within a freezer. It's usually independent of the other systems of the refrigerator. Ice maker systems have two basic functional components: the icemaker itself, and the water fill valve. More indepth information on ice makers is available in the ice maker section.

Ice and water dispenser

There are several different systems for delivering ice and water through the refrigerator door. What follows is an explanation of the common attributes of all of the systems:

  • Ice dispenser - For a refrigerator to provide ice through the door, the ice maker first dumps the ice it produces into a large bin. To request ice at the door, a person presses a lever that activates a switch. The switch turns on a motor that rotates the auger. When the auger rotates, it pushes ice out of the bin, through a chute to the user.
  • Water dispenser - The water dispenser works much like the ice dispenser. To request water at the door, a person presses a lever on the front of the refrigerator that activates a switch. The switch turns on an electric water valve at the back of the refrigerator. Water flows through the valve into a tube, then flows into a container in the refrigerator to be chilled. As new water enters the container, the water that is displaced flows through a separate tube to the user.

Door seals and hinges

All refrigerator/freezer doors have a rubber-like gasket or seal attached to the door. Usually white, almond, black, or brown, the seal's job is to keep the cool air inside the refrigerator and the room air out.

  • The seal is lined with a magnet that runs its length and width. The magnet helps to hold the door closed and create a tight seal. The screws that hold the seal to the door also hold the door liner in and help to "square" the door.
  • The hinges allow the door to swing open. Some hinges also assist the door in closing. For the door to close properly, the hinges must be correctly adjusted.


Proper installation of a refrigerator is both easy and important. The primary concerns are that the unit has sufficient clearance from the walls for proper ventilation, that it is not pinching any electrical cords or water lines, and that it is level. Many refrigerators must be tilted back slightly so that the doors self-close. Consult your owner's manual for further installation instructions.

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