When sizing and selecting a valve, it must be ensured that – in the controlled operating state – the output does not drop below the minimum controllable output Qmin. Otherwise, the controlling element only regulates in on/off mode within the range of the initial flow surge. On/off mode reduces the plant’s energy efficiency and adversely affects the controlling element’s life.
The rangeability SV is an important characteristic used for assessing the controllable range of a controlling element.
The smallest volumetric flow kvr that can be controlled is the volumetric flow passing through the valve when it opens. Output Qmin is the smallest output of a consumer (e.g. of a radiator) that can be controlled in modulating mode.
For more detailed information on the subject, refer to the brochure "Hydraulics in building systems" (ordering no. 0-91917-en).