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Unistream 5 Pro : internal clock stopped without reason


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Hello everyone, 

This is my first message on the UniForum, and I'm a frenchie, so sorry for bad english.

There is a limit on a number of schedule modules in an unistream program ? 

I made a program to manage a boiler room. I have multiple schedules to modulate the temperature (day, night ect.) and schedule to pilot an lighting extinction from 9pm to 6am

Sometimes, the clock of the PLC stops at 8pm 59minutes. (1 sec before my lighting extinction schedule) Everything elese in the program work great, all my PID in the program works, ect. BUT, the plc clock is stopped, so my schedules are also freezed (sorry if the expression is wrong). 

If I go to the UniApps, I can see the clock is been stopped, if I click on it, and I try to change date/time, the PLC don't apply the new date/time, and I have no error message, and also no CPU bugs ect.

If I want the PLC works again with my schedules I have to shutdown and restart. And magically everything comes back, with the correct date/time...

So, I contact the french disributor of Unitronics (PLSystem), they ask me to do theses things :

  • Update firmware to the latest version = Done, no ameliorations
  • Download an empty project on the PLC and redownload the projet, and do some tests = Dome, no ameliorations
  • Upload to them, the UniLog file, but they don't find any precious info in it.

Last chance, change the PLC to a new one, but it's in production, we are in winter, it's not possible to stop boilers. So I have to wait May/June to do this. 

Maybe some of great and genious people here, can give me some indications, or solutions... 

I have something to tell you as well : i'm a begineer (I'm 25) in the Unitronics world. (I normally program Schneider PLC).

Thanks to all.


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  • MVP 2023

Florian, after doing Saragani's advice I also suggest that you think about having an alternative, independent, less capable control on each boiler that you can switch things over to very easily.

All the 24/7 HVAC systems I do have sophisticated control by the plc(s), but if something should go wrong there is basic control available with a few switch changes that the owners can do to keep things running well enough until I can problem solve.  So far this has never happened, but the ability is there if ever needed.

Come May/June you might like to think about implementing something like this.

cheers, Aus

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