Thermostatic radiator valves are typically used for regulating the medium flow to the radiators in a heating systems. When combined to a thermostatic control head, they keep the ambient temperature of the room where they are installed constant at the set value. This prevents unwanted temperature rises and achieves considerable energy savings. This reversible thermostatic radiator valve may be fitted in the flow or return pipe of a domestic central heating system. The valve should be positioned so that the sensor head is horizontal and can detect the temperature of the air in the room. The sensor must not be shielded by curtains or other similar obstructions and should not be exposed to direct sunlight.