Defrosting control of air-conditioning apparatus

Abstract

A method for controlling an air-conditioning apparatus in terms of execution of the defrosting mode. The apparatus basically includes a variable-frequency compressor, a room heat-exchanger for performing heat-exchange with a room fan, and an outdoor heat-exchanger provided at the outside of the room, which are circularly coupled to each other to establish a refrigerating cycle. Also included in the air conditioning apparatus are a bypass circuit provided between a first line for effecting a connection between an outlet side of the compressor and the room heat-exchanger and a second line for effecting a connection between an inlet side of the compressor and the outdoor heat-exchanger and a restriction device arranged to allow a change of its restriction amount and provided between the two heat-exchanger. The bypass circuit has an opening and closing valve for shutting off the bypass circuit. In response to start of a defrosting mode for defrosting the outdoor heat-exchanger, the restriction amount of the restriction device is controlled so as to be reduced as compared with that on the heating mode, the opening and closing valve is opened for establishing communication between the first and second lines, and further the compressor is controlled so that its operating frequency is increased stepwise up to a predetermined value desirable for the defrosting mode.