| 摘要 |
PURPOSE:To ensure pleasant heating with no waste of heat for a heat pump type heating device incorporating a defrosting circuit, by providing a time delay element between a heat-sensitive element and a comparator which compares the detection value of the said element and the set value. CONSTITUTION:The resistance value of a thermistor 1, i.e., a heat-sensitive element that detects the temperature of a heat exchanger provided in the outside of room has a negative temperature coefficient, and the terminal voltage decreases as the temperature increases. The voltage of such thermistor 1 is applied to the negative phase input terminal of a voltage comparator 2 via a time delay element consisting of an integral resistance 3 and an integral capacitor 4. For instance, if the temperature lowers with the voltage of the element 1 exceeding the set value, the output of the comparator 2 reduces. As a result, a relay 7 works to change the heating operation to a defrosting mode. In such case, the output of the comparator 2 is fed back to the positive phase input terminal via a resistance 8 to lower the set value down to the defrosting stop voltage. In such way, the possibility for start of the defrosting operation can be eliminated during an application of the power source in case the temperature of a heat exchanger provided in the outside of room is higher than the defrosting start temperature. |
