Abstract: An object of the present invention is to reduce electrical noise in accordance with the necessity of a countermeasure taken against electrical noise without changing a structure of an expansion valve. In a case where a judgment result as to whether or not the countermeasure against electrical noise is taken is affirmative, a drive timing (interval) of an expansion valve (107) is increased. Further, a driving amount is reduced. Accordingly, a flow of a refrigerant is made slow, whereby it is possible to reduce generated electrical noise while performing instructed temperature control.

Abstract: After the power source to the control substrate is turned on, power is supplied to the compressor driver and the fan driver. Then, when it is determined that an indoor unit is in operation, the compressor driver and the fan driver are operated. Meanwhile, when it is determined that the indoor unit is not in operation, after the lapse of ten minutes or twenty minutes under a predetermined setting, the power to the compressor driver and the fan driver is cut. When the operation of the indoor unit is started again, power is supplied to the compressor driver and the fan driver.

Abstract: A serial number detection portion simultaneously transmits a detection command for requesting a first digit of a serial number to plurality of indoor units, and the serial number detection portion simultaneously transmits a detection command for requesting a second digit immediately preceding the first digit to the indoor units when a response to the detection command is absent. That is, the address setting is performed again from the immediately preceding digit without returning to an initial digit of the serial number, so that the time necessary for the address setting can be shortened. When the address setting is performed again from the immediately preceding digit, the address setting can be performed more securely by changing a method of recognizing the detection command in the indoor units.

Abstract: A normality determination unit determines that a communication function for an outdoor unit of its own is normal when receiving a signal from one of indoor units, and writes a normality flag into an EEPROM. Further, the normality determination unit determines that it is not asserted that the communication function for the outdoor unit of its own is normal when not receiving a signal from any of the indoor units for a predetermined time period, and deletes the normality flag in the EEPROM.

Abstract: An object of the present invention is to reduce electrical noise in accordance with the necessity of a countermeasure taken against electrical noise without changing a structure of an expansion valve. In a case where a judgment result as to whether or not the countermeasure against electrical noise is taken is affirmative, a drive timing (interval) of an expansion valve (107) is increased. Further, a driving amount is reduced. Accordingly, a flow of a refrigerant is made slow, whereby it is possible to reduce generated electrical noise while performing instructed temperature control.

Abstract: A serial number detection portion simultaneously transmits a detection command for requesting a first digit of a serial number to plurality of indoor units, and the serial number detection portion simultaneously transmits a detection command for requesting a second digit immediately preceding the first digit to the indoor units when a response to the detection command is absent. That is, the address setting is performed again from the immediately preceding digit without returning to an initial digit of the serial number, so that the time necessary for the address setting can be shortened. When the address setting is performed again from the immediately preceding digit, the address setting can be performed more securely by changing a method of recognizing the detection command in the indoor units.

Abstract: A normality determination unit determines that a communication function for an outdoor unit of its own is normal when receiving a signal from one of indoor units, and writes a normality flag into an EEPROM. Further, the normality determination unit determines that it is not asserted that the communication function for the outdoor unit of its own is normal when not receiving a signal from any of the indoor units for a predetermined time period, and deletes the normality flag in the EEPROM.

Abstract: After the power source to the control substrate is turned on, power is supplied to the compressor driver and the fan driver. Then, when it is determined that an indoor unit is in operation, the compressor driver and the fan driver are operated. Meanwhile, when it is determined that the indoor unit is not in operation, after the lapse of ten minutes or twenty minutes under a predetermined setting, the power to the compressor driver and the fan driver is cut. When the operation of the indoor unit is started again, power is supplied to the compressor driver and the fan driver.