Evohome + HGI80 & Domoticz users - zones calling for heat functionality?

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  • Ditbenik
    Automated Home Lurker
    • Dec 2016
    • 7

    Thank you for your explanation. Now I have another question. Because I think I spill a lot of energy bij firing up the boiler while the valves are closed I had an idea of overriding my evohome controller. Just for an experiment. Ik was looking at the events section in Domoticz. My idea was to read the temperatures. As long as the temperatures are not more then 0.3 degree below setpoint the whole system should be shut down (by giving a command that the controller goes in economy position). Is the temperature lower than I will raise alle temperatures far above setpoint. (this way i will be sure the pump is running and the valves are open). Then when the temperature comes to the setpoint the whole system is again set in economy mode. In my case I think (because are house is very well isolated with an Rc value 8) the heating system will be off most of the day, because cooling down goes very slowly. But when I try to do that by scripting using blocky the only temperature I can read out is the outside temperature (for which I have a device). All the devices for the evo home temperatures are not seen. Is this normal?

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    • DanD
      Automated Home Ninja
      • Feb 2016
      • 250

      Quick Domoticz update:

      I've finally fixed the bug which prevented the DHW sensor's battery information appearing in the devices list. The fix has just been merged into the main Domoticz code and should appear in the next beta in a week or so.

      I'm working on fully implementing the Opentherm Bridge with Bruce's help at the moment. I'll hopefully have an update ready in the next week or so and it's looking likely that the only information available is the heat demand message (0-200) which gives some indication of the flow temperature (0-min 200-max). I still have to complete some further investigations to confirm this though.

      Dan

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      • dty
        Automated Home Ninja
        • Aug 2016
        • 489

        Dan, my DHW is set to 58, but the demand in Domoticz shows as 60. Any thoughts? I can capture you a few messages if that's useful (and you can tell me the message ids).

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        • DanD
          Automated Home Ninja
          • Feb 2016
          • 250

          @dty

          Unfortunately, Domoticz doesn't yet know how to request the DHW setpoint and differential so it's just pre-set in the graphs at 60. It's on my to-do list to fix this in the code as the command is known (10A0). It's a little more involved to fix as I need to squeeze the multiple values (setpoint, differential and possibly overrun) into the Domoticz data structure without breaking something else.

          Dan

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          • dty
            Automated Home Ninja
            • Aug 2016
            • 489

            Fairy snuff! I'll shut up! Just having the right set-point without the other stuff would be an awesome start and stop me getting confused.

            Out of interest, what is the "differential"? I can see the actual DHW value, and it seems like you know how to get the set-point. What else is there?

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            • DanD
              Automated Home Ninja
              • Feb 2016
              • 250

              No, please don't shut up . The more users that ask about a feature the more likely it is to rise to the top of my to-do list. To make it enjoyable, I have to find something to finish every few weeks. So, I'm often switching tasks when I hit a roadblock.

              The differential gives you the lower temperature (setpoint minus differential) which triggers the DHW to re-heat. There's also the overrun setting in the controller menu which keeps the DHW valve open for the specified time after the boiler demand has stopped to extract further heat (I'm not 100% sure that this value is sent in the 10A0 message though).

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              • dty
                Automated Home Ninja
                • Aug 2016
                • 489

                That makes sense. I'd call that hysteresis, or trigger level, or something.

                Not sure what benefit there is to sending in the message though? Perhaps the OT Gateway uses it to blend DHW and CH demand into a final heat demand from the boiler?

                Comment

                • DBMandrake
                  Automated Home Legend
                  • Sep 2014
                  • 2361

                  The differential is just another name for hysteresis yes.

                  I think you're confusing the hot water sensor and OpenTherm bridge - the hot water differential is sent in the communications between controller and CS92A. The CS92A is informed of the user set hot water set point and differential so that it's battery saving algorithm can make better decisions about when to transmit temperature updates.

                  Below setpoint-differential updates are very infrequent (once an hour I think) unless there is a change of several degrees. In the differential range updates are much more frequent (about one per degree rise) and when the set point is crossed an update is always sent immediately to avoid heating past the set point.

                  To do this the controller has to be able to communicate to the CS92A what the set point and differential actually are.
                  Last edited by DBMandrake; 9 February 2017, 06:53 PM.

                  Comment

                  • dty
                    Automated Home Ninja
                    • Aug 2016
                    • 489

                    Originally posted by DBMandrake View Post
                    The differential is just another name for hysteresis yes.
                    Maybe. I was just saying what I'd call it!

                    Originally posted by DBMandrake View Post
                    I think you're confusing the hot water sensor and OpenTherm bridge.
                    Not at all. I just hadn't considered that the controller might broadcast that information at all, let alone for the benefit of the temperature sensor! Do you have an evidence that the CS92A does what you've described? That would be pretty clever if so.

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