PURPOSE: To accomplish quick balancing of the high and low pressure by making the restarting of the compressor impossible for the required time length and leaving all electromagnetic valves for passing the refrigerant open for the required time after the operation of the room unit is halted.

CONSTITUTION: With operaton switches 18 and 19 on, the first and second electromagnetic valves 32 and 33 for passing the refrigerant are opened to drive a compressor 21 and a blower 24 to perform cooling operation. Meanwhile, when both the switches are turned off, contacts D, F and G of a relay 28 moves to the position as shown by the solid line and a coil 23 of a relay 22 is turned off to halt the compressor 21 and the blower 24. A heater 26 of a thermal timer 25 is turned off and then returns to the position as shown by the solid line in about 3 minutes after the cooling (the cooling of two different kinds of metal). Therefore, a contact 27 stays at the position as shown by the dotted line for both the electromagnetic valves 32 and 33 to be continually energized. Thus, the refrigerant is made to pass so that a proper balance is taken quikly between the high and low pressures.