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How Does a Refrigerator Work?

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Side-By-Side Unit

Side-By-Side Unit

How Refrigerators Work

All frost-free refrigerators operate on the same principles. They have a closed system that is controlled by the use of timers and controls.

  1. The way it works is that refrigerant is compressed into a liquid in a closed system and is sent to the freezer through a tube where it is allowed to expand back into a gas state. When it expands, it actually absorbs heat.
  2. Then it is sent through a tube back to the compressor, where it is compressed into a liquid again, giving off a lot of heat.
  3. There are coils in two places. The coils located in the freezer compartment behind a panel or wall are called the evaporator coils. The coils located near the compressor, located on the bottom or back of the refrigerator, are called the condenser coils.

That is the basic idea of how it works; the refrigerant cycles in and out of the refrigerator, absorbing and releasing heat. This cycle operates on a continuous loop to keep the refrigerator at a constant temperature.

Understanding Your Refrigerator's Temperature Controls

The refrigerator would get too cold if it ran all the time. It needs to turn off when it is cold enough and turn back on when things start warming up.

Cold Control

The on-off function is controlled with a device called a cold control. This is a device that uses an adjustable thermostat to sense the temperature inside the unit, turn off when it is cold enough, and turn back on when the temperature rises.

The adjustable part of the thermostat is controlled with a dial that is usually located inside the refrigerator. The numbers normally range from 0 (off) to 9 (coldest). Some may have fewer numbers, and some have more, but the largest number is the coldest setting.

Coldness Dial

Most refrigerators also have another dial that is normally labeled AIR or FREEZER and has letters or numbers that indicate the level of coldness. Usually, the letters are A, B, and C, where A = warmest, B = normal, and C = coldest.

If it is labeled with numbers, it most likely is 1 to 5, 1 to 7, or 1 to 9, with 1 being the warmest setting and the largest number being the coldest. This control has a link to a door or slide that opens and closes to allow more or less air from the freezer to circulate into the refrigerator section. This control does not actually control the cold—it controls the air that circulates between the freezer and the refrigerator.

Fortunately, most manufacturers label the two controls with a suggested normal setting. With a new refrigerator, the recommended settings are the place to start.

If you have a refrigerator that has been working fine for the past couple of years and now the temperatures are not low enough, adjusting the controls may help temporarily, but a change in the operation of the refrigerator is an indication that the unit may be developing problems.

Cold Control

Cold Control

Frost-Free Defrost Cycle

Most frost-free refrigerators have a defrost cycle that is timed and uses a heater to melt the frost on the evaporator coil in the wall (usually the back wall) of the freezer compartment. Yes, several times a day, a heater comes on and warms up the coils in the freezer to melt any frost that might build up.

The temperature in the wall of the freezer is limited to somewhere between 45 and 65 degrees. When the temperature reaches the correct temperature, the heater is turned off by the defrost thermostat, which is a simple on/off switch set to turn off at a specified temperature.

For the defrost cycle, there is a timer that turns the refrigerator off from 2 to 4 times a day for about 20 minutes each time. The frost that is melted produces a small amount of water that is drained through a tube that goes from the floor of the freezer to a small pan near the compressor. The condenser fan blows hot air over the pan holding this warm water to evaporate it away.

Air Control

Air Control

Refrigeration System

Do-it-yourself repairs on a refrigerator should be limited to all the systems outside of the sealed system. The sealed system (consisting of the compressor, condenser coils, and evaporator coils) should only be serviced by authorized technicians.

I would say that most of the problems with a refrigerator are related to other devices and controls. Armed with information, it is possible to fix most problems.

To summarize, the refrigerator is a complete system that operates a complex set of tasks on a timed and temperature-sensitive schedule. It actually is a pretty amazing machine. If you take care of it, you will have many years of use.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


JIMAYY on December 06, 2011:


Refrigeration on January 10, 2011:

Thanks for a great explanation. There are a lot of badly written articles on this kind of thing on the web, so it's good to read something concise. I remember when refrigeration was first explained to me, my teacher said, 'when you wet your finger and blow on it, and it feels cold - that's refrigeration at work'. I thought it was a good way of explaining an unintuitive concept. Thanks!

SteveoMc (author) from Pacific NorthWest on December 11, 2010:

@Sam s You are welcome, glad it was helpful information. Thanks for reading.

Sam S on December 11, 2010:

Thank you for taking the time to post the intructions for proper air flow control (1 to 7). A simple adjustment really but very vital to not freezing all my food.(The milk frozen solid was the last straw..AAARRRGGG) Thanks again.

SteveoMc (author) from Pacific NorthWest on November 08, 2010:

@Aaron H Actually you are completely wrong about the refrigerator control. Almost always the refrigerator dial controls the temperature in the refrigerator with a thermostat called a cold control that has capillary tube located in the refrigerator section. You are right about it controlling the compressor (motor).

The way it works is that the temperature control is actually an on-off switch. When the temperature in the refrigerator section reaches the proper temperature, the control turns the compressor off.

You are correct that the freezer control changes the air flow.

Most refrigerators work just the opposite of what you prefer, and they are very safe and have been used and designed that way for many years.

A few models have temperature controls located in the freezer and this method works well too.

The freezer is where the evaporator coil is located and the coldest temperatures, this is the location of the fan that circulates the air. The model shown demonstrates a typical model where the freezer control is used to control the air flow.

This is why manufacturers recommend changing the control only once in a 24 hour period so that the refrigerator can balance.

Aaron H on November 06, 2010:

Actually, on most fridge/freezers, the fridge temperature control knob just controls the amount of air that enters the fridge, not the freezer control. I think on the model shown, the fridge setting controls the motor. The freezer control changes the amount of air that enters the fridge. Therefore, on its coldest, the freezer will be cold, and the fridge will run longer to keep the fridge cold. However, the colder air in the freezer might actually help cool things down quicker. I prefer models that have the freezer controlling temperature and the fridge control controlling the amount of air from the freezer. I don't think its safe having a control like the one on the model shown here

BJBenson from USA on April 30, 2010:

Thanks for the information.