Refrigerator - Frost Guard / Adaptive Defrost
Frost free refrigerators defrost automatically using either a time-based system or usage-based system. Most older refrigerator models and some current Top Freezer refrigerator models defrost based on time, regardless of whether or not it is necessary.
Adaptive Defrost (Frost Guard) Definition:
Adaptive Defrost means that the refrigerator will only defrost as needed. It accounts for door openings and usage to determine when it is necessary to defrost and how long the defrost cycle needs to run. If the refrigerator is not being frequently used (for example, your family is on vacation), it will not defrost as often.
The Adaptive Defrost (Frost Guard) feature also utilizes a "Pre-Chill" function to lower the freezer temperature prior to the defrost cycle. This lowering of the freezer temperature allows the freezer to return to its set temperature point more quickly once the defrost cycle is complete. All of this amounts to minimal thawing of foods and refreezing during the defrost cycle. The result is that it reduces freezer burn.
How Does this System Adapt?
In order to accomplish the correct amount of defrost cycle time, the main control board monitors the following refrigerator operations:
Length of time the refrigerator doors were opened since the last defrost cycle.
Length of time the compressor has run since the last defrost cycle.
Amount of time the defrost heaters were on in the last defrost cycle.
This information is collected by the main control board and is used in the 5 separate cycles that make up the Adaptive Defrost (Frost Guard) cycle:
Cooling Operation: During the cooling operation, the main control board monitors door openings (fresh food and freezer doors) and compressor run times. The board counts the times that the doors are opened. The board then adjusts how soon the refrigerator goes into defrost.
Pre-Chill: When the main control board determines that the defrost cycle is necessary, the main control board will force the refrigerator into a continuous cool mode (this is Pre-Chill). The Pre-Chill will last for 2 hours if the doors are not opened.
Defrost Heater Operation: The main board turns off the compressor, condenser fan and evaporator fan. During the defrost heater operation, the main control board monitors the evaporator temperature using the evaporator thermistor inputs. The thermistor input is what terminates the defrost heater operation. A typical defrost cycle lasts 20-30 minutes.
Dwell Period: After the main board has terminated the defrost operation, a five minute Dwell Period occurs. During the Dwell Period the compressor, condenser fan and evaporator fan remain off. The remaining frost that melts from the evaporator will continue to drip and drain so that the evaporator will be totally clear of any moisture.
Post Dwell Period: The Post Dwell Period is designed to cool the evaporator before circulating air within the refrigerator. This prevents any residual heat on the evaporator from being distributed in the freezer.