DEFROSTING CONTROL CIRCUIT FOR AIR HEAT SOURCE HEAT PUMP TYPE REFRIGERATING PLANT

摘要

PURPOSE:To prevent the deterioration of energy consuming efficiency due to the reduction of a pressure as well as the stopping of a refrigerating device due to the operation of a low pressure protecting device by a method wherein the operation of the refrigerating device is switched into defrosting operation automatically when a pressure is reduced to the set value of a pressure intercepting device detecting a suction pressure or evaporating pressure upon heating operation. CONSTITUTION:A timer 13 is constituted so as to measure an elapsed time after finishing defrosting by a contact 52 closed after finishing defrosting operation while a pressure switch 12 for detecting a vapor pressure or a suction pressure is constituted so as to be closed when a pressure is reduced to a pressure lower than a set pressure. When the vapor pressure or the suction pressure is reduced to a value lower than the set pressure after elapsing a given time (set time of the timer 13) after finishing defrosting, current is conducted through an auxiliary relay 5 through contacts 1, 2, a selective switch 11, the time limit contact 131 of the timer 13 and a pressure switch 12 whereby defrosting operation is started. Accordingly, the deterioration of performance due to the reduction of the vapor pressure or the operation of a low pressure protecting switch can be prevented.