| 摘要 |
PROBLEM TO BE SOLVED: To shorten defrosting time and to conduct defrosting without causing interruption on heating operation. SOLUTION: In the heating operation, the gas discharged from a compressor 1 goes through a four-way valve 2 and three-way valve 9, flows through an indoor heat exchanger 8 to be subjected to heat exchange with air, and turns condensate. This passes through a two-way valve 7 and undergoes pressure reduction in an expansion valve 6, and it passes through a four-way valve 3, flows through an outdoor heat exchanger 4 to be subjected to heat exchange with outdoor air and turns low-temperature and low-pressure gas, which returns to the compressor through the four-way valve 2. In the case a temperature sensor 10 is provided on the side of the outdoor heat exchanger, the four-way valve 3 is turned 'OFF'. In the case of defrosting the outdoor heat exchanger, the expansion valve 6 is opened, with the heating operation being left conducting, restriction being made by the expansion valve 5 and defrosting being executed by making the part of b to the expansion valve 5 operate as a condenser, while an opening-closing valve 12 is opened to make the gas from the compressor flow to facilitate the defrosting and heat is absorbed from the outdoor air, by making the part of the expansion valve 5 to a operate as an evaporator. Thus heating operation is conducted. After the part of b to the expansion valve 5 has been defrosted, the four-way valve 3 is switched over and the part of a to the expansion valve 5 is defrosted similarly as above, while the part of the expansion valve 5 to b is made to operate as the evaporator to conduct the heating operation.
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