The temperature is controlled via the wall thermostat, which measures the room temperature and sends it to the radiator thermostats. The radiator thermostats then regulate based on the temperatures they measure directly at the radiator. The maximum adjustable temperature for radiator thermostats is not usually specifically stated, but is typically around 28 degrees Celsius for most heating systems.

If your radiator is behind a cover, this may affect the accuracy of the measurement. It is advisable to position the thermostat so that it measures the room temperature accurately.