PURPOSE: To prevent an abnormal rise or fall of the temperature in the refrigerating tank due to a faulty operation of a change-over valve for room cooling and space heating by stopping the operation of a refrigerating plant when the change-over device makes a faulty operation, which is known from a change in the temperature of the coolant that flows out from an evaporator, a change in the temperature of the air sucked into the evaporator or a change in the temperature of the air blown out from the evaporator.

CONSTITUTION: For example, when in the cooling operation the inside of a refrigerating tank is cooled to a set temperature, Ts and a three-way valve 5 is switched by the instruction of the thermostat TH1 of a controller 22 and heating operation is carried out, the detected temperature Ta by a temperature sensor 21 when the instruction is given and the detected temperature Tb after a specified time has passed from the time of the instruction are inputted to a controller 22. Here, if Ta>Tb, it is discriminated that the operation of the three-way valve 5 is fault and it is notified by an abnormality display means 23. An engine 1 stops based on the instruction of the controller 22 and the operation of a refrigerator is stopped. It is, therefore, possible to prevent an abnormal rise or abnormal fall of the temperature inside the refrigerating device that is caused by a faulty operation of the change-over device, and the quality of the objects that are refrigerated is kept normal.