Functional questions

What is the CSV format used by Hysopt ?

The Hysopt software allows to update various configuration values using CSV files. The CSV format is a fairly relax specification to represent tabular data in a simple text format. Often, CSV files will be formatted differently according to the regional settings of the system.

Hysopt uses a FIXED format :

  • UTF-8 File Encoding

  • ; (semicolon) as field separator

  • . (dot) as the decimal separator

  • No quotes around values

Example snippet:

evaporatorTemperature;condenserTemperature;modulation;cop -15;25;0.3;2.84491071428571 -15;30;0.3;2.624375 -15;35;0.3;2.44121822033898 -15;40;0.3;2.2866796875 -15;45;0.3;2.15453804347826

Excel will typically natively open CSV files. Depending on your regional settings this will lead to incorrect representation. Similarly if you save an Excel sheet as CSV, it may not match our required format.

Full coverage of instructions on how to safely work with CSV files in Excel is beyond the scope of this FAQ. Nevertheless, some quick advice and warnings:

  • When you use the ‘Data > From Text/CSV’ menu option, you have more control over the loading of the data

  • UTF-8 is referred to as ‘codepage’ 65001 in Windows. (Will be mentioned potentially as File origin)

  • When auto-detection inappropriate interpretes . as a thousand seperator, you should use the Transform Data function. Using the transformation tool, you can FIRST replace the . by your local decimal separator and then mark the colums as decimal numbers. NOTE: When you had to do this operation, you will face similar issues when saving the document to CSV from Excel !

  • When you saved your document from Excel as CSV (UTF-8), please check the produced text output using a text editor and check the field and decimal seperators ! Convert them appropriately using the text editor functions if needed.

How can I enable MFA (Multi Factor Authentication)

Go to the user settings

and activate MFA

Follow the instructions on the screen.
You’ll need an authenticator application like :

How can I modify pressure profiles for pipes during pipe selection?

See Select pipes

How can I change the mouse button used to pan the canvas? 

Go to the user settings to change the mouse behavior :


How can I track and analyse the history of changes within a model? 

In the load/save window, click the 'history' icon next to the model you want to investigate.

In the history window, you can investigate who made changes to your model. You can also select two version of your model that you want to compare to see the differences.

By clicking on the compare button, you download an excel file with an overview of all the changes between the two versions. Example :

The simulation of my model crashes or is very slow, what do I have to do?

  1. Verify if you see error messages during design computations. If so, fix them before doing the simulation.

  2. Verify the error messages and see if you can change your model based on the error message and its suggestions

  3. If you have a parallel production base circuit, make sure the volume flows cannot become negative in one of the two production parts (by adding the necessary control logic or non-return valve) (HYS-3800)

  4. If you use ILS components, please verify the following page: Imposed Load Simulation (ILS) error codes and common mistakes

  5. If your model has a pump with a 'proportional head' mode, please check if you can simulate the 'constant speed' of the 'constant head' mode

  6. If you have a PI controller directly controlling a pump, try to switch to a PI controller controlling a valve (HYS-3538)

  7. If your model contains PICVs (Pressure Independent Control Valve) or DPCVs, please try the following :

    1. Set "enable P-Control simplification" of the DPCV to false
      if you have locked the primary design pressure, you might need to tune the proportional band

    2. change the valve type of the control valve behind the DPCV from equiprocentual to linear

    3. add randomness on the setpoint profiles of the rooms

    4. enable the 'smoothen DPCV lift curve' parameter

    5. raise the SVO value to 100 (smoothens the lift curve)) of the control valve behind the DPCV

    6. <not advised> In the 'setting overrides', go to the 'Expert Settings' tab and higher the Iteration target

  8. Please contact Hysopt (

My browser ran out of memory, I get the message “Aw Snap! Chrome ran out of memory“. What do I need to do?

First, walk through the troubleshooting list on following webpage :

If you tried every step and you still encounter memory issues, please contact Hysopt (

Why does exporting to PDF sometimes yield a poor-quality print for larger models?

The current "Export to PDF" feature yields a bitmap image, which by its nature is limited in terms of image resolution. This style of exporting differs from vectorial formats one would typically see when working in CAD environments. The main parameter in determining optimal readability is the "DPI"-setting (dots per inch). We support settings from 75 up to 300 DPI. Combining this with the correct page size selection should yield a perfect export.

To verify the source of potential quality problems when printing, we suggest first ensuring the PDF export itself is readable when zoomed in.

Some Hysopt users import the Export PDF into a different application to do post-processing (markup, branding, adding metadata). We have noticed that it is typically in this step where there is a loss of resolution/quality. We, therefore, urge our users to contact the vendors of those applications for support in dealing with large bitmap images, such as the Hysopt exports.

What are the folders "Projects", "Sandbox", "Templates", and "Legacy Files"?

See the documentation here: Folder structure and project identification

My folder structure is “messed up“, and therefor the load/save dialog of Hysopt does not seem to work correctly anymore

Disable automatic translations in Google Chrome, see