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.

Cooling
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.

Lighting
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 seal--a rubber-like gasket 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.

Installation
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.

Refrigerator Buying Tips

Types

Top-Mount freezer refrigerators - A top-mount fridge has the freezer at eye level, with the fresh food compartment on the bottom. These refrigerators generally have wider shelves in both the fridge and freezer sections.

Side-by-side refrigerators - The refrigerator and freezer compartments are next to one another and allow easy access to both compartments. The side-by-side can have shelves that are narrower than those found in top or bottom freezer models. If possible select a model with adjustable bins and shelves so that you can customize the layout to suit your storage needs. Make sure you have the capacity to get the type of food you eat into the unit, will that pizza box or gallon milk jug fit on the shelf?

Freezer on Bottom - The bottom mount freezer is a good option for households that want to use less energy, want fresh food selections at eye level, and want their food kept at a more consistent and even temperature. This configuration requires less bending to reach for food, as the most frequently used section, the refrigerator is located in the top compartment for easy access.

French Door - An increasingly popular style of refrigerator that has dual refrigerator doors and a pullout freezer drawer for convenient fresh and frozen food storage. This style combines the best features of the Bottom Mount and Side-by-Side refrigerators.

Capacity

Selecting the correct size for your needs is very important. If you buy one that is too big and don't keep it filled, it wastes energy and costs more to operate. If it is too small, you waste time constantly rearranging food trying to make it all fit. Consider your space requirements for both the fresh food and frozen food.

Style, Design and Special Features

Refrigerators are typically the biggest appliance in the house, it's also the most visible feature in your kitchen, a room where most families spend a lot of time. The options seem almost endless to create the "look" of your refrigerator. Some of the options include:

• Counter-depth refrigerators that are flush with your cabinets.
• Custom doors that can be contoured or matched to your cabinet face.
• Colors to match any decor - even retro designs are offered today.
• Adjustable glass shelves, wine racks, ice storage bins, spill proof shelves, clear storage bins, door mounted drink and ice dispensers, child locks for drink dispensers, thawing and defrosting compartments, and advanced lighting options are all available on today's refrigerators.
  

Tricks to Keep Your Refrigerator Maintained

Manual-defrost refrigerator/freezers - require very little maintenance. If you notice frost build-up of ½ inch or so in the freezer, remove the food from the refrigerator and freezer, turn off the thermostat or just unplug the unit. Once the frost has melted, wipe the inside of the refrigerator and freezer to clean up any food spills and dry the surface. Turn the unit back on, wait for it to reach its operating temperature, then restock it with food.

Self-defrosting refrigerator/freezers - do not need to be manually defrosted. Every 6 to 8 hours self-defrosting refrigerator/freezers will automatically heat up its cooling coils slightly and melts any frost accumulation on the coils. The resulting water drains into a shallow pan at the bottom of the refrigerator/freezer.

• There's no need to empty the pan. The water in it will evaporate. But it may begin to smell bad over time. You may be able to remove it for periodic cleaning by detaching the lower grill and sliding the pan out the front of the refrigerator/freezer.

Note… When mold grows in the drain pan, it is sometimes considered to be a health concern. If your drain pan is removable, and if you're sensitive to mold, consider cleaning the drain pan periodically.

General Cleaning

• Under your refrigerator/freezer is a set of coils and a cooling fan that you need to clean at least once a year. The coils may look like a grate or like a wide radiator. Unplug the refrigerator/freezer and use a Refrigerator Condenser Brush, and your vacuum cleaner to clean any lint, pet hair, and so on from the coils.
• Keep the gasket or interior of the refrigerator/freezer clean to help extend the life of the appliance.
• For odors in the refrigerator/freezer try baking soda or, for tougher odors, try Fridge Aid deodorizer.