Thermostatic expansion valve for refrigeration or heat-pump circuits with thermally controlled safely function

Thermostatic expansion valve for regulating a high pressure of a refrigeration or heat-pump circuit which is operatable both transcritically and also subcritically, having a valve housing in which, at the input side, a high pressure prevails in a supply opening, and at the output side, a low pressure prevails at a discharge opening, having a valve element which, for the throughflow of the refrigerant, closes and moves in the opening direction a valve seat of a passage opening arranged between the supply opening and the discharge opening, and which is assigned to a first actuating element, the first actuating element comprising a chamber which is delimited with a first active face and which contains a control charge, characterized in that an actuating element is provided, which is thermally activated independently of the high pressure, the actuating movement of which actuating element is coupled in terms of movement to the first active face of the first actuating element when a temperature-dependent actuating movement of the thermally activatable actuating element acts counter to the actuating movement of the first active face of the first actuating element, with a temperature threshold value of the thermally activatable actuating element for an actuating movement being set to an identical value as the MOT (maximum operation temperature) of the control charge of the first actuating element, which control charge has a fluid density which lies below its critical density.