HVAC Functions

Persistent variables are stored in text files on the controller using the Application Composers Persistent Manager. This allows the settings to be stored by the user at any time and up-to-date on the controller and thus made available again during a cold boot. The files can also be stored externally. If you change the controller, the settings can be restored. Even operating conditions can, for example, be stored after commissioning and can be re-read as desired. For these files to be saved, the stored variables must be provided with an attribute, and in the project, the files must be created in the Application Composer. To do this, create two channels in the Application Composer using the Persistence Manager. The names of the two channels must be the same as the description of the attributes used in the library. (With the example project, the channels have been created. An example video on our YouTube channel explains persistent behaviour in more detail.

There are two different files: - HVAC_Parameter (for parameters of the parameter window of all FBs) - HVAC_Counter (for operating hour data or other counter data)

The attributes before the variables are then:

For HVAC_Parameter:

{attribute 'ac_persist' := 'HVAC_Parameter'}

For HVAC_Counter:

{attribute 'ac_persist' := 'HVAC_Counter'}

Why two files? The HVAC_Parameter file is configured in such a way that if changes occur in the parameters, the file is immediately rewritten on the system (save with changes). Since the changes only occur when the user actively changes settings, this does not happen so often.

The HVAC_Counter file contains operating hour counters or pulse counters. These values ​​constantly change according to the runtime. So that the file does not write over the memory all the time, cyclic storing is used here (e.g. every 12h, adjustable).

If the parameters are changed offline, the parameter list must be deleted before going online and a new one is created. However, all other online values ​​will then be lost!