Method for controlling defrost in refrigeration systems

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

• a digital controller for measuring temperatures and regulating the operation of the refrigeration system including initiating the 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;
• wherein the proportionalities and relationships among the specified elements are essential to achieve the objectives of said defrost system;
• and wherein;
• the volume of said product storage chamber to the volume of said TVMC is nominally 4.6 having 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 is nominally 0.8 (in3/J/g)) having 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.