Defrosting system for a heat exchanger

A defrosting system for a heat exchanger comprising:

• a temperature detector adapted to be arranged in close proximity to a heat exchanger;
• a temperature memory for storing temperature data detected by the temperature detector;
• a first timer for counting a defrosting prohibitive time;
• a second timer for counting the time required to complete the defrosting operation;
• a switching means for switching the flowing direction of a refrigerant to the heat exchanger;
• and
• a central processing unit for controlling the temperature memory, the first and second timers, and the switching means, and further carrying out arithmetic manipulations;
• wherein the central processing unit sets the next prohibitive time depending on the time counted by the second timer;
• and
• when a second temperature which is detected by the temperature detector after normal operation requested by a user has restarted and after a predetermined minimum defrosting prohibitive time has passed, drops by a predetermined difference in temperature from a first temperature which is detected by the temperature detector after the normal operation has restarted and after a predetermined time has passed, and when the second temperature is a predetermined temperature or below;
• the central processing unit carries out the defrosting operation even if the prohibitive time has not passed.