To eliminate any inconvenience in summing-up processing when an abnormal state occurs during communicating operation by a method wherein after a calculating function part confirms that there is no abnormal state in communication between an intervening function part and the calculating function part, each of the operation times stored in the intervening function part is collected.

For example, an intervening processor 81 has a processing part 81A in which it sums up each of operating times over a predetermined time each time when each of indoor devices 12,...1n performs an air conditioning operation, stores them while being classified for every predetermined time and the stored content of the operating times is given to a charge summing-up machine 100 as data value. The processing part 81A may receive a communication between a processing part 11B of a heat source machine 11 and each of the processors 12,...1n of each of the indoor devices 12,...1n through a communication line 61A. Then, the processing part 81A may transmit a code corresponding to a communication address and a confirmation of communication, for example, when a communication signal to start a charge calculation is transmitted and if it is judged that there is no abnormal state in it, the processing part may transmit subsequently data of the operating time and the reference data.