How Defrost Works In Refrigerators/Freezers

Fred's Appliance
November 26, 2014


Most modern-day refrigerators have a built-in mechanism that automatically removes frost from the evaporator. Known as auto-defrost or self-defrosting, this feature is essential for controlling the frost inside refrigerators and freezers. While most people are familiar the general concept of auto-defrost, few people know how the system works.


Refrigerators and freezers are designed to keep food and beverages fresh by creating a cool environment that’s below the freezing point of water. Over time, however, a layer of ice will form around the unit’s evaporator coil, restricting the cool air from passing into the unit. The ice acts as an insulator, making the refrigerator work twice as hard to try and stay cool.
Defrosting solves the problem of ice build-up on the evaporator by melting the frost. When the atmosphere surrounding the frost-covered evaporated rises above 32 degrees Fahrenheit, the frost will begin to melt. Some of the early model refrigerators required manually defrosting by disconnecting power to the unit for a given period of time. Thankfully, most modern-day refrigerators and freezers have an auto-defrosting function.


Refrigerators and freezers with auto-defrost usually have a temperature control mechanism that tells the unit when to stop cooling. There’s still power running to the unit, but when the internal temperate reaches the specified setting, it will stop blowing cool air into the main compartment until the evaporator has defrosted.


Some of the benefits of auto-defrost in refrigerators includes the following:


  • Better air circulation, which subsequently improves the shelf-life of food and beverages stored inside the refrigerator.
  • Prevents foods from sticking together.
  • Helps control the refrigerator’s internal temperature.
  • Discourages foul odors from forming.


Of course, there are also some disadvantages to auto-defrost as well. Due to the increased complexity of its mechanical components, repairs and maintenance on auto-defrost refrigerators are more difficult. And just because the defrost timer cycles back to zero doesn’t necessarily mean the evaporator is frost-free. If there’s a lot of humidity in the surrounding air, frost may linger on the evaporator coils – even after the auto-defrost has kicked in.


Hopefully this will give you a better understanding of the auto-defrost function in refrigerators and freezers. Auto-defrost is found in just about every modern-day refrigerator and freezer, and for good reason: it’s an essential feature to keep the unit working as intended. If frost builds up on the evaporator, the unit won’t be able to maintain its cool internal temperature.

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