PURPOSE: To improve pleasantness and the operation efficiency of a heat pump by a method wherein detectors for detecting the relative humidity of the open air and the temperature in an outdoor heat exchanger are provided and the necessity of performing a defrosting operation is detected accurately.
CONSTITUTION: A humidity sensor 8 is connected to an input terminal of a microcomputer 9 and a thermosensor R1 of the outdoor heat exchanger 6 is connected to the input terminal of the computer 9 through a comparator 10. Further, a transistor Q1 is connected to an output terminal of the computer 9 and a relay coil 11 connected to the collector terminal of the transistor Q1 controls the switching of a four-way valve 2 by opening and closing of a relay terminal 12 of constant use. When, during a heating operation, the temperature in the piping of the outdoor heat exchanger 6 drops below a predetermined value, the input voltage V(+) of the comparator 10 goes higher than a reference voltage V(-) and when the relative humidity of the open air is higher than a predetermined value, the humidity sensor 8 turns ON whereupon the transistor Q1 and the relay coil 12 are turned ON by the computer 9 so that the four-way valve 2 is switched to set the air conditioner in a defrosting operation mode. However, the mere lowering of the temperature of the outdoor heat exchanger 6 is insufficient for setting the air conditioner in the defrosting operation mode.
SHIMOKAWA NAOKI
OOSHIRO SHIGERU
MORIKAWA HISASHI
