PURPOSE: To prevent a fault of a freezing cycle from occurring by providing means to enter into a defrosting operation with a succeeding space heating operation in a space time which is shorter than the preceding lowest space heating time in a case where a defrosting terminating condition is not satisfied within the defrosting largest time.
CONSTITUTION: When a maximum defrosting time t2 comes before an outdoor heat exchange outlet coolant temperature 25 reaches a set value, the defrosting operation is terminated at this time point. In this case, the shortest operation time t1 of space heating is substituted for t1-t, and the succeeding shortest space heating time is reduced by a time t, and a flag is set to Fr=Fr+1. On the other hand, in a case where the heat exchanger 5 outlet coolant temperature 25 is more than a set value f, if Fr is not 0, the shortest space heating time is set to t1$-t, and if the space heating time becomes more than the largest space heating time t12, the defrosting operation is forcibly started. In this manner, when the flag Fr becomes equal to a set number (y), a defrosting extraordinariness display is made. Further, in a case where the flag Fr becomes equal to the number of setting (z), the operation of the freezing cycle can be stopped, and the fault in the freezing cycle can be prevented.
KOKUNI KENSAKU
YASUDA HIROSHI
