How it works? When the three elements have been assembled together, the valve installed and the sensor located at the point where the temperature is to be regulated, the function sequence is as follows: The pressure changes in the sensor as a result of a change in temperature - builds up in the sensor. This pressure is transferred to the valve via capillary tube and bellows and acts as an opening or closing force. The knob on the setting section and the spring exert a force that acts counter to the bellows. When balance is created between the two opposing forces, the valve spindle remains in its position. If the sensor temperature changes – or if the settings are changed – the point of balance becomes displaced and the valve spindle moves until balance is re-established, or the valve is fully open or closed. The ow quantity change is approximately proportional to sensor temperature change