Patent ID: 7841196

Claim:
A variable-capacity air conditioner comprising: a compressor operable at a first capacity and a second capacity less than the first capacity to compress a refrigerant; an indoor heat-exchanger coupled to the compressor; an outdoor heat-exchanger coupled to the compressor; a piping for coupling the compressor, the indoor heat-exchanger, and the outdoor heat-exchanger; a first capillary tube provided in the piping; a second capillary tube provided in the piping, the second capillary tube being connected in series with the first capillary tube; a by-pass pipe connected in parallel to the second capillary tube; a valve for opening and closing the by-pass pipe; a controller for controlling the compressor and the valve such that the variable-capacity air conditioner operates in three stages; and a voltage detector for detecting a voltage applied to the compressor, wherein in a first stage, the controller is programmed to (1) open the valve independent of the detected voltage and (2) operate the compressor at the first capacity independent of the detected voltage, to provide a first flow rate of the refrigerant, in a second stage, the controller is programmed to (1) open the valve when the detected voltage is lower than a predetermined value and (2) operate the compressor at the second capacity independent of the detected voltage, to provide a second flow rate of the refrigerant smaller than the first flow rate, and in a third stage, the controller is programmed to (1) close the valve when the detected voltage is equal to or higher than the predetermined value and (2) operate the compressor at the second capacity independent of the detected voltage, to provide a third flow rate of the refrigerant smaller than the second flow rate.