Method for controlling defrost in refrigeration systems

A refrigeration defrost system for a refrigerator wherein said refrigeration defrost system is used for storage of vaccines or other products having such low temperature storage requirements, said refrigeration defrost system comprises:

• a digital controller for measuring temperatures and regulating the operation of the refrigeration system including initiating a refrigeration defrost cycle;
• a condenser having metal tubing ranging in length from 180 to 240 inches;
• a hermetically sealed compressor;
• an evaporator having metal tubing ranging in length of 80 to 160 inches;
• wherein said evaporator further having fins for heat transfer and an integrated heating element and an expansion device, wherein said evaporator is positioned in an evaporator chamber;
• when said heating element of said evaporator becomes hot when subjected to an electrical current;
• a product storage chamber for storing vaccines or other products having low temperature storage requirements;
• an axial airflow induction fan;
• a temperature variance moderation chamber (hereinafter TVMC);
• a plurality of thermal reservoirs arranged and disposed in the TVMC;
• a dividing plenum wall dividing said TVMC from said product storage chamber, wherein the evaporator chamber is separated from the product storage chamber by the TVMC, the plurality of thermal reservoirs of the TVMC and the dividing plenum wall acting as a thermal barrier between the evaporator chamber and the product storage chamber;
• and
• wherein the volume of said product storage chamber to the volume of said TVMC has a range from 3 to 5.5;
• and
• wherein the volume of the product storage chamber relative to said thermal reservoirs total latent heat ratio has a tolerance zone of 0.1 to 1.5 (in3/J/g));
• and
• wherein the temperature of said product storage chamber maintains a temperature of −58 degrees Centigrade and −15 degrees Centigrade during the defrost cycle of the refrigerator.