Abstract: By studying or storing refrigerating cycle characteristics of an air conditioning apparatus at the normal time and comparing them with refrigerating cycle characteristics acquired from the air conditioning apparatus at the time of operation, it becomes possible to exactly and accurately diagnose normality or abnormality of the air conditioning apparatus under any installation conditions and environmental conditions, which eliminates operations of inputting a difference between apparatus model names, a piping length, a height difference, etc at the time of apparatus installation. Accordingly, it aims at shortening the time of judging normality or abnormality, and improving the operability.

Abstract: By studying or storing refrigerating cycle characteristics of an air conditioning apparatus at the normal time and comparing them with refrigerating cycle characteristics acquired from the air conditioning apparatus at the time of operation, it becomes possible to exactly and accurately diagnose normality or abnormality of the air conditioning apparatus under any installation conditions and environmental conditions, which eliminates operations of inputting a difference between apparatus model names, a piping length, a height difference, etc at the time of apparatus installation. Accordingly, it aims at shortening the time of judging normality or abnormality, and improving the operability.

Abstract: An air conditioner has a refrigeration circuit formed by sequentially connecting a compressor 1, a condenser 2, an electronic expansion valve 4 and an evaporator 7 by pipes (6, 10). A compressor bypass pipe 12 is provided to connect an outlet of the evaporator 7 with an inlet of the condenser 2. A first on-off valve 11 is located in the bypass pipe 12. The air conditioner is controlled to switch to either a forced circulation operation or a natural circulation operation. In the forced circulation operation, the first on-off valve 11 is closed, the expansion valve 4 is opened to a first degree to allow refrigerant to pass therethrough, and the compressor 1 is operated in a running state. In the natural circulation operation, the first on-off valve 11 is opened, the expansion valve 4 is opened to a second degree, different from the first degree, to allow refrigerant to pass therethrough, and the compressor 1 is stopped.

Abstract: A multi-air-conditioner includes an exterior unit, interior units and remote-controllers. The exterior unit collects operation data of each of the interior units, determines an operation condition, and transmits the operation condition to each of the interior units. The interior units transmit the operation condition to the exterior unit, receive the operation condition from the exterior units, receive the operation setting condition from the remote-controllers, set an operation condition based on the operation setting condition which is received from the remote-controllers and the exterior unit, and transmit the operation condition to the remote-controllers. The remote-controller receives the operation condition from the interior units and transmits the operation setting condition to the interior units.

Abstract: A control apparatus for a multi-air-conditioner having an external unit and a plurality of internal units includes a DC electric power supply. An external transmitting/receiving circuit is provided with the external unit and is connected with the DC electric power supply, and a plurality of internal transmitting/receiving circuits are provided with the plurality of internal units and are connected serially with the external transmitting/receiving circuit via a signal line. A DC voltage is supplied for transmitting data from the external unit to the internal unit, which reduces a leakage distance of the circuit. A timing for transmitting data can be set freely, a transmitting speed of data can be improved using a high-speed photo-coupler, and thus an operation speed of the internal unit can be improved in the multi-air-conditioner having the plurality of internal units.