How to eliminate: "Cannot determine Dpmin on valve"

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Product InstalSystem 5
Type of article TIP&TRICK
Source for translation 2022-03-15

Problem description

Minimum pressure drop across the Valve component is helpful, in the case of valves installed near or on terminal units, in obtaining the required authority; in addition, for some valve types (e.g. Δp controller) manufacturers recommend a specific value of Δpmin. For the calculation, the value is taken from the valve data table and can be changed individually there. Problems related to the program's inability to achieve the set Δpmin are identified by the message:

cannot determine Dpmin on valve

The above message appears when:

  • Valve has no settings (has a specified kv value) and has no thermostatic head,
  • for the smallest setting the flow through the Valve does not produce the required pressure drop.


In most cases, the diagnostic message cannot determine Dpmin on valve can be left without responding to it. In the case of a mass occurrence of the message for the Valve component on/near the terminal units, and therefore when there is a concern of obtaining too low authorities, the following can be done:

  • use, if available, valves or integrated valves with a lower kv range,
  • increase the flow rate through the terminal units in question by reducing their calculated temperature drop. However, the final cool down value in the terminal unit is determined by the Adjust flow rates option, which is enabled by default in the General data, Radiator sizing options window..
    1. Adjust flow rates