Adaptive refrigerator defrost method and apparatus

A method for defrosting a refrigeration unit including an evaporator, a defrost heater, and a controller operatively connected to the evaporator and the defrost heater, the controller including a defrost counter, said method comprising:

• initiating a defrost cycle to energize the defrost heater to defrost the evaporator;
• selecting a low temperature defrost cycle when the defrost counter is less than a predetermined value;
• and
• selecting a high temperature defrost cycle when the defrost counter equals said predetermined value.

A method for defrosting a refrigerator including a sealed system, an evaporator, a defrost heater, and a controller operatively connected to the evaporator and a defrost heater, the controller including a defrost counter and a defrost timer, said method comprising:

• initiating a defrost cycle to energize the defrost heater to defrost the evaporator;
• selecting a low temperature defrost cycle when the defrost counter is less than a predetermined value;
• selecting a high temperature defrost cycle when the defrost counter equals the predetermined value;
• terminating the low temperature defrost cycle by de-energizing the defrost heater when a first temperature termination point of the evaporator is reached when the low temperature defrost cycle is selected;
• terminating the high temperature defrost cycle by de-energizing the defrost heater when a second temperature termination point of the evaporator is reached when the high temperature defrost cycle is selected, the second termination temperature higher than the first termination temperature;
• comparing an elapsed defrost time to a reference defrost time when either of the high temperature defrost and low temperature defrost are terminated;
• selecting a normal or abnormal defrost interval based upon the compared elapsed defrost time and reference defrost time;
• and
• operating the sealed system for the selected defrost interval.

A refrigeration defrost unit for an evaporator, said defrost unit comprising:

• a defrost heater;
• a controller operatively coupled to said defrost heater;
• and
• a thermistor adapted for sensing a temperature of the evaporator, said controller configured to operate said defrost heater in a low temperature defrost mode de-energizing said defrost heater at a first temperature in response to said thermistor, and to operate said defrost heater in a high temperature defrost mode de-energizing said defrost heater at a second temperature in response to said thermistor, said second temperature higher than said first temperature.

A refrigeration unit comprising:

• a compressor;
• an evaporator;
• a defrost heater;
• and
• a controller, said controller operatively coupled to said compressor, said evaporator and said defrost heater, said controller comprising a defrost timer and configured to operate said compressor in a normal mode and an abnormal load in response to a value of the defrost timer, and said controller further comprising a defrost counter and configured to operate said defrost heater in a high temperature defrost mode and a low temperature defrost mode based upon a value of said counter.

A refrigerator comprising:

• a cabinet defining at least one refrigeration compartment;
• a sealed system for cooling said at least one refrigeration compartment;
• a defrost heater;
• and
• a controller operatively coupled to said sealed system and to the defrost heater;
• said controller configured to adaptively control said defrost heater and said sealed system in a high temperature defrost mode and a low temperature defrost mode between normal and abnormal defrost intervals.