TRNFlow errors and solutions

TRNFlow, an option for airflow networks in TRNSYS, allows you to configure airflow networks based on a multi-zone model (Type 56/TRNBuild). In addition to the thermal model, the same model can also take into account the effects of natural and mechanical ventilation.

In some cases, TRNFlow generates a different kind of error than the thermal model.

The airflow network must be configured with one network.

When saving a file in TRNBuild, you may occasionally see a message like the one in the screen capture. This is a screen capture of an attempt to save a sample in “C:\TRNSYS18\Examples\TRNFLOW_example” that was intentionally edited to generate an error.

TRNFlow error message

The airlink network is not properly connected.
All Airflow nodes must be connected in ONE network.
Please check the INF-file for future information.

What causes the error?

In this example, the airflow networks are not concentrated into a single network. (In fact, there are multiple airflow networks in the model, which causes the error.)

If you follow the message and open the .INF file with Notepad, you will find the following error message.

TRNFLOW (2003-06-04) based on COMIS 3.1

Copyright (C) 2001 EMPA



All zones should be connected, but here are 2 isolated groups of zones.
You have to add links, or delete not-used zones from &-NET-ZONes.
You have to add at least 1 link between those groups.
Zones in group 0 are not in &-NET-LIN or are connected only toknown pressure(s).

Here follow the zones and the group they are in.
Zone Group Zone name:
4 2 AN_001
5 2 AN_006
6 2 AN_005
7 2 AN_002
8 2 AN_003
9 2 AN_004


COMIS MESSAGE ***** ERROR *****The Network is not properly connected:

The airflow network must be connected to one network, but this message shows that there are two independent airflow networks.

If If you continue reading the message, you will see the following. Here you can see what groups are exist.

Zone, Group and Zone name

The number in the red frame of the figure is the group number. There are two independent groups, No.1 and No.2.

For the sake of clarity, I have colored them in, and they are divided into the DINING and STORAGE group (No.1) and the other group (No.2).

The airflow network is shown in the figure below.

Looks like one airflow network

At first glance, it looks like one airflow network, but if you look closely, you can see that the External node divides the network into DINING and STORAGE group and other group.

There are two airflow networks.


Modify the thermal zone in the building to configure a single airflow network by connecting the KITCHEN to the DINING or STORAGE via Large Opening or Crack.

The following figure shows an example of an airflow network in “C:\TRNSYS18\Examples\TRNFLOW_example”.
You need to configure it so that it is all in one airflow network as shown in the figure.


Test Environment

It has been confirmed that the software works in the following environments.

  • Windows10 Pro(64bit, 21H1)
  • TRNSYS18.02.0002(64bit)

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