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  • DBMandrake
    Automated Home Legend
    • Sep 2014
    • 2361

    #46
    Originally posted by paulockenden View Post
    I don't understand this single/multiple zone thing with Intergas. The boiler doesn't KNOW how many zones there are. It's simply getting an aggregated heat demand from the controller.
    To put it politely, the "not compatible with multiple zones" is bull dust...

    There is nothing in the OpenTherm spec to even make the boiler aware that a system might be zoned. What does zoned mean anyway ? Does a system with manual TRV's count as a "zoned" system ? Of course. Every zone can independently control the flow of water through it's radiator(s).

    How many heat demands are sent to an OpenTherm boiler if you have a traditional single-zone thermostat ? One.

    How many heat demands are sent to an OpenTherm boiler if you have a multi-zone system like Evohome, where individual zones can call for heat, and the demand is aggregated ? Still One.

    The spec doesn't allow for communication of multiple zone heat demands, and even if it did, what would the boiler do with that information ? A boiler can only output one flow temperature on the heating circuit at a time.

    In short, it's a nonsense excuse from Intergas for a problem that can't exist. Clearly there is some sort of issue with their OpenTherm support but it's nothing to do with not being able to handle a multi-zone system like Evohome.

    bruce_miranda's suggestion may be closest to the truth - if Intergas is one of the boilers that can't limit the maximum flow temperature in OpenTherm mode and you have a complex schedule where there are frequently rooms increasing their set points it could well lead to a situation where the flow temperature is very high a lot of the time, where it wouldn't be on a single zone system, making it semi-useless.

    However if this is the real issue, Intergas are certainly not alone, and it's getting to the point where Honeywell need to act and provide a maximum OpenTherm flow temperature setting in the Evotouch software. (Where you would expose it in the user interface I'm not sure though, as it would need to be a bit more prominent than being hidden in the installer menu, as mere mortals would need to be able to adjust it as the seasons changed...)

    Has anyone here actually used Intergas OpenTherm with Evohome and if so what are the symptoms you notice (if any) ?
    Last edited by DBMandrake; 2 July 2017, 11:09 PM.

    Comment

    • blowlamp
      Automated Home Sr Member
      • Apr 2017
      • 98

      #47
      When an OpenTherm controller is connected to a (in this case Intergas) boiler, the onboard controller surrenders that control and becomes its slave in all but the most fundamental ways.

      As the relationship is now one of master & slave, then amongst other things it becomes the task of the offboard controller to set and maintain flow temperature (including max), so expecting the onboard controller to limit the excesses or inadequacies of the offboard controller isn't how OpenTherm is designed to work.

      As far as I am aware, Intergas have never implied this fault lies with their boiler, let alone issue an excuse for it.
      Also, Intergas are based in the Netherlands where OpenTherm is mandatory, so it'd be fair to assume they have a decent understanding of what's required for it to work.

      Please take a look at the manual at this link to see the functions of a dedicated OpenTherm control.

      Download specification guides, installation manuals, technical datasheets, BIM files, CAD files, and ErP documentation on the Remeha product range here.





      Martin.
      Last edited by blowlamp; 3 July 2017, 01:17 AM.

      Comment

      • HenGus
        Automated Home Legend
        • May 2014
        • 1001

        #48
        Originally posted by DBMandrake View Post
        To put it politely, the "not compatible with multiple zones" is bull dust...

        There is nothing in the OpenTherm spec to even make the boiler aware that a system might be zoned. What does zoned mean anyway ? Does a system with manual TRV's count as a "zoned" system ? Of course. Every zone can independently control the flow of water through it's radiator(s).

        How many heat demands are sent to an OpenTherm boiler if you have a traditional single-zone thermostat ? One.

        How many heat demands are sent to an OpenTherm boiler if you have a multi-zone system like Evohome, where individual zones can call for heat, and the demand is aggregated ? Still One.

        The spec doesn't allow for communication of multiple zone heat demands, and even if it did, what would the boiler do with that information ? A boiler can only output one flow temperature on the heating circuit at a time.

        In short, it's a nonsense excuse from Intergas for a problem that can't exist. Clearly there is some sort of issue with their OpenTherm support but it's nothing to do with not being able to handle a multi-zone system like Evohome.

        bruce_miranda's suggestion may be closest to the truth - if Intergas is one of the boilers that can't limit the maximum flow temperature in OpenTherm mode and you have a complex schedule where there are frequently rooms increasing their set points it could well lead to a situation where the flow temperature is very high a lot of the time, where it wouldn't be on a single zone system, making it semi-useless.

        However if this is the real issue, Intergas are certainly not alone, and it's getting to the point where Honeywell need to act and provide a maximum OpenTherm flow temperature setting in the Evotouch software. (Where you would expose it in the user interface I'm not sure though, as it would need to be a bit more prominent than being hidden in the installer menu, as mere mortals would need to be able to adjust it as the seasons changed...)

        Has anyone here actually used Intergas OpenTherm with Evohome and if so what are the symptoms you notice (if any) ?
        This guy has and issues are also reported on Richard's forum:

        I installed Evohome over 2 years ago. I am now looking to replace a 16 year old boiler with either a Viessmann, ATag or Intergas product using an Opentherm connection. I know that the Viessmann 100 needs a HW junction box for HW priority; the Atag needs an EBus to Opentherm converter and...

        Comment

        • DBMandrake
          Automated Home Legend
          • Sep 2014
          • 2361

          #49
          Originally posted by HenGus View Post
          This guy has and issues are also reported on Richard's forum:

          https://www.diynot.com/diy/threads/i...#ixzz4lh9XvW9v
          Yep,

          We've all seen that thread from October last year before in previous discussions - but it doesn't go much beyond speculation. The poster (whoever they are) is just relaying Intergas's claim that the problem is due to not modulating with multiple zones, but offers no technical details to back up this claim.

          They then go on to speculate that there is "too much data" coming from the OpenTherm bridge, but that is pure unsubstantiated speculation and to be honest, as someone who works in computers and has done a little bit of embedded development, I don't buy this argument for a second.

          In short, we really don't know what the issue is, but I cannot see how it can be related to having multiple zones. It just seems like another case of a poor OpenTherm implementation.

          Comment

          • DBMandrake
            Automated Home Legend
            • Sep 2014
            • 2361

            #50
            Originally posted by blowlamp View Post
            When an OpenTherm controller is connected to a (in this case Intergas) boiler, the onboard controller surrenders that control and becomes its slave in all but the most fundamental ways.
            And being able to limit the maximum flow temperature is a pretty fundamental thing, is it not ?
            As the relationship is now one of master & slave, then amongst other things it becomes the task of the offboard controller to set and maintain flow temperature (including max), so expecting the onboard controller to limit the excesses or inadequacies of the offboard controller isn't how OpenTherm is designed to work.
            So you think it's OK for a boiler to completely surrender control of the flow temperature to an OpenTherm master with no checks or balances or even a maximum limit ? So if the controller asks for 100 degrees the boiler should just do it even if it overheats ?

            Clearly different boilers are going to have different maximum flow temperatures that they can support, so they should place a sensible limit on the maximum that they will accept, even if only for their own protection. How is the controller supposed to know what is best for a given boiler ? Just because the OpenTherm master is nominally in charge doesn't mean it should have free reign.

            Perhaps by disabling local limits when under OpenTherm control the boiler is still following the letter of the protocol spec, but that doesn't mean it is following the spirit of the spec. Sometimes sanity has to intervene. The fact that some boilers do let you limit the maximum flow temperature under user control even when being controller by an OpenTherm master shows that it can be done.

            I suspect this is just a case of yet another not quite sufficiently defined protocol that leaves too much up to the implementers interpretation, and therefore interoperability issues arise. The frustrating thing is that neither party seems to want to take a step to improve the functionality of their device to be more compatible with the other, and instead seem to want to take up a "not our problem - we're following the spec" stance.

            Comment

            • HenGus
              Automated Home Legend
              • May 2014
              • 1001

              #51
              Originally posted by DBMandrake View Post
              Yep,

              We've all seen that thread from October last year before in previous discussions - but it doesn't go much beyond speculation. The poster (whoever they are) is just relaying Intergas's claim that the problem is due to not modulating with multiple zones, but offers no technical details to back up this claim.

              They then go on to speculate that there is "too much data" coming from the OpenTherm bridge, but that is pure unsubstantiated speculation and to be honest, as someone who works in computers and has done a little bit of embedded development, I don't buy this argument for a second.

              In short, we really don't know what the issue is, but I cannot see how it can be related to having multiple zones. It just seems like another case of a poor OpenTherm implementation.
              I still struggle to understand when a manufacturer that developed the Opentherm protocol would not implement it correctly in its product range. I return to my earlier plea to Honeywell to spell out how they expect an Evohome/Opentherm connected boiler to respond to Opentherm control both in HW and CH modes?

              Comment

              • HenGus
                Automated Home Legend
                • May 2014
                • 1001

                #52
                This link takes you to a Belgian website. Click on CV half way down the page and it shows the boilers that they believe are Evohome/Opentherm compatible.



                The Intergas RF range does not appear to be in the list ( country model number difference?) and some boilers with known problems are in the list. Interestingly, they call Evohome 'single zone'.

                Comment

                • paulockenden
                  Automated Home Legend
                  • Apr 2015
                  • 1719

                  #53
                  Originally posted by HenGus View Post
                  Interestingly, they call Evohome 'single zone'.
                  Which is effectively what it is, as far as the boiler is concerned.

                  P.

                  Comment

                  • HenGus
                    Automated Home Legend
                    • May 2014
                    • 1001

                    #54
                    I have just had a courtesy call from Atag so I raised this ongoing discussion about Evohome/Opentherm. One of their technical guys will get back to me. Of interest, I have just found this on the Vokera website:

                    Quote: When the OpenTherm control is installed it overrides the controls on the boiler fascia. For example the OT Control will override the heating and hot water temperature settings on the boiler fascia. So your OT controller is now the means by which you control your heating system and boiler. It also overrides any other room thermostat or time control previously fitted to the system which may still be connected. Unquote

                    The above statement does beg the question about 3rd party opentherm controls which don’t have the ability to set boiler parameters, or is this set up bespoke to Vokera controls with one their own boilers?

                    Comment

                    • blowlamp
                      Automated Home Sr Member
                      • Apr 2017
                      • 98

                      #55
                      Originally posted by HenGus View Post
                      I have just had a courtesy call from Atag so I raised this ongoing discussion about Evohome/Opentherm. One of their technical guys will get back to me. Of interest, I have just found this on the Vokera website:

                      Quote: When the OpenTherm control is installed it overrides the controls on the boiler fascia. For example the OT Control will override the heating and hot water temperature settings on the boiler fascia. So your OT controller is now the means by which you control your heating system and boiler. It also overrides any other room thermostat or time control previously fitted to the system which may still be connected. Unquote

                      The above statement does beg the question about 3rd party opentherm controls which don’t have the ability to set boiler parameters, or is this set up bespoke to Vokera controls with one their own boilers?


                      The first part of the quote is exactly how our Intergas boiler works with its Remeha iSense controller. I don't know what would happen with additional connected thermostats as we don't have any.

                      I have no reason to think Vokera is unique in how it implements OpenTherm on its controls. I'd be fairly confident that the Isense would work OK if connected to a Vokera boiler and likewise with their controller connected to our Intergas boiler, althought I'm sure that certain advanced features would differ.

                      As a minimum, I'd expect flow temperatures to be handled seamlessly, no matter how the components are mixed. By that I mean I'd expect to be able to set a room temperature in the knowledge the system is taking care of adjusting flow temperature - and to stay in condensing range if possible - without me having to specify it.


                      Martin.
                      Last edited by blowlamp; 4 July 2017, 11:24 PM.

                      Comment

                      • HenGus
                        Automated Home Legend
                        • May 2014
                        • 1001

                        #56
                        To digress slightly, it would seem that posters worried about Evohome over-riding their boiler flow set temperature when heating water may just be seeing normal opentherm operation. The question that I have asked Atag is whether they are happy with a controller that can demand 90C flow temperatures when their boiler specification gives a maximum of 85C flow temperature in the technical specification? That said, if my observation of my Atag is anything to go by, I suspect that the answer will be that boiler set temperature is not being over-ridden by Evohome. I have also been able to reduce the max CH flow temperature on the boiler controls. In sum, I am not sure that I am any the wiser.

                        Comment

                        • HenGus
                          Automated Home Legend
                          • May 2014
                          • 1001

                          #57
                          Originally posted by HenGus View Post
                          To digress slightly, it would seem that posters worried about Evohome over-riding their boiler flow set temperature when heating water may just be seeing normal opentherm operation. The question that I have asked Atag is whether they are happy with a controller that can demand 90C flow temperatures when their boiler specification gives a maximum of 85C flow temperature in the technical specification? That said, if my observation of my Atag is anything to go by, I suspect that the answer will be that boiler set temperature is not being over-ridden by Evohome. I have also been able to reduce the max CH flow temperature on the boiler controls. In sum, I am not sure that I am any the wiser.
                          Edit:

                          I have just checked boiler temperatures again after my DH ran a bath. The boiler profile is set to a max flow temperature of 70C. The output flow was showing 70C, TSet 70C and a return temperature of 65C. Clearly, the boiler is over-riding Evohome Opentherm. I suspect that if I changed the boiler profile to 80C the boiler max flow temperature would respond accordingly.

                          Looking at Atag's own interpretation of an Opentherm control. It has the usual end user settings but nothing in the controller to control boiler temperatures. Indeed, the manual makes it very clear that these are set on the boiler.

                          Comment

                          • blowlamp
                            Automated Home Sr Member
                            • Apr 2017
                            • 98

                            #58
                            What is normal under OpenTherm is that the settings that are able to be made on the master controller override the equivalents on the boiler controller. The boiler is thus controlled by those constraints programmed into the master controller, that is, the master controller becomes the boiler controller except for the more fundamental features such as overheat protection, ignition problem lockout & range rating etc.

                            What isn't normal (for me) under OpenTherm is persistant demand at full CH output for 'topping-up' lost heat where a lower flame height would suffice.

                            In contrast to the Atag controller you mention, the Remeha manual I linked to on the previous page of this thread (starting ~ page 20) details the included CH settings which do have priority on my system. Also note towards the end of the document the official OpenTherm logo and the V3.0 specification.

                            Comment

                            • bruce_miranda
                              Automated Home Legend
                              • Jul 2014
                              • 2307

                              #59
                              Originally posted by HenGus View Post
                              Edit:

                              I have just checked boiler temperatures again after my DH ran a bath. The boiler profile is set to a max flow temperature of 70C. The output flow was showing 70C, TSet 70C and a return temperature of 65C. Clearly, the boiler is over-riding Evohome Opentherm. I suspect that if I changed the boiler profile to 80C the boiler max flow temperature would respond accordingly.

                              Looking at Atag's own interpretation of an Opentherm control. It has the usual end user settings but nothing in the controller to control boiler temperatures. Indeed, the manual makes it very clear that these are set on the boiler.
                              The Valliants also work this way. But bear in mind the Valliants also have a VR33 stuck in the middle between boiler and OT bridge, which could easily be affecting the way the two interaction. In fact if you query the eBUS of the Valliant boiler it has both values i.e. Temp being demanded by the OT bridge as well as Max Temp it is trying to get to as restricted by the boiler controls. The Flow temp will only ever get to the lower of those two values i.e. Demanded or Boiler set.

                              Comment

                              • dty
                                Automated Home Ninja
                                • Aug 2016
                                • 489

                                #60
                                Originally posted by bruce_miranda View Post
                                The Valliants also work this way. But bear in mind the Valliants also have a VR33 stuck in the middle between boiler and OT bridge, which could easily be affecting the way the two interaction. In fact if you query the eBUS of the Valliant boiler it has both values i.e. Temp being demanded by the OT bridge as well as Max Temp it is trying to get to as restricted by the boiler controls. The Flow temp will only ever get to the lower of those two values i.e. Demanded or Boiler set.
                                I'm increasingly unconvinced by this. See this graph:

                                boiler-overshoot.jpg

                                I'm colour-blind, so I struggle to describe this graph. The line that goes highest of all is the eBus requested temp. The spike is at 90C. The line "inside" that, is the boiler's actual target temp, and is the same as the eBus temp, except it's capped at the temp configured on the boiler - in my case 75. This /appears to be/ the temperature the boiler aims for, but it doesn't always manage. If you look at the two lines that slowly slope down during the first half of the period, the higher one is the flow temp, the lower one is the return temp. But look at 14:50... The flow peaks just over 80C (despite the boiler being configured for 75C, and having a "physical max" of 80C).

                                Compare and contrast this graph:

                                boiler-power.jpg

                                This shows a period of heating the DHW. In this case, the eBus request is for 90, the boiler targets 75, and hits it pretty much spot on, and then gradually modulates the flame down (the bold line) as the return temps climb as the delta-T inside the cylinder narrows and there is less and less heat extracted.

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