Ideal Vogue & Opentherm via Honeywell T6 Lyric (wired version)

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  • richardc1983
    Automated Home Sr Member
    • Nov 2016
    • 86

    #91
    Originally posted by DBMandrake View Post
    Not really.

    If you specify a target flow temperature using OpenTherm the boiler will modulate the burner kW output as necessary to meet and maintain that requested flow temperature.

    If you were to specify a target burner output in kW directly using OpenTherm (which I don't think it can do anyway) the flow temperature that you ended up with would be all over the place depending on the load presented by the radiators, so wouldn't provide any useful control.
    So what do you think ideal are on about then?

    Comment

    • bruce_miranda
      Automated Home Legend
      • Jul 2014
      • 2307

      #92
      I read "Burner Output" as the Trigger to fire the burner. How can an OT determine what size the burner output should be? It should just demand a certain flow temperature and maybe have control of when the Burner fires.

      Comment

      • richardc1983
        Automated Home Sr Member
        • Nov 2016
        • 86

        #93
        I thought opentherm controlled the pump also.

        Comment

        • dty
          Automated Home Ninja
          • Aug 2016
          • 489

          #94
          Originally posted by richardc1983 View Post
          I thought opentherm controlled the pump also.
          No, the boiler controls the pump.

          My Vaillant will quite happily run the pump without the burner if the demanded flow temperature suddenly drops - i.e. it will circulate the hot water already in the system to meet demand until enough heat has been lost that it needs to fire up the burner again.

          Comment

          • Strat789
            Automated Home Lurker
            • Nov 2017
            • 2

            #95
            Originally posted by dty View Post
            No, the boiler controls the pump.

            My Vaillant will quite happily run the pump without the burner if the demanded flow temperature suddenly drops - i.e. it will circulate the hot water already in the system to meet demand until enough heat has been lost that it needs to fire up the burner again.
            I looked at the OpenTherm Specification: the Master OT Plus (Opentherm Bridge, T6 and Evohome etc) can request control of the Slave (Boiler) Flow rates and the Set Temp. as required. There isn't anything in the Spec. about control of the Slave gas flow.

            Also, in the Specification, it describes the difference between OT Plus (OT/+) and OT Lite (OT/-) - the main difference is: if no (OT/+) handshake is sent back from the Slave to the master (after a control request from the master) the master goes into OT/- mode ie the Boiler is treated as dumb ....a simple on/off system that responds to heat requests from the Master OT.

            In OT/+ Mode: there is loads of monitoring/control data is passed back from the Slave to the Master eg Modulation (status is on/off) Return temp etc etc

            Comment

            • richardc1983
              Automated Home Sr Member
              • Nov 2016
              • 86

              #96
              Originally posted by Strat789 View Post
              I looked at the OpenTherm Specification: the Master OT Plus (Opentherm Bridge, T6 and Evohome etc) can request control of the Slave (Boiler) Flow rates and the Set Temp. as required. There isn't anything in the Spec. about control of the Slave gas flow.

              Also, in the Specification, it describes the difference between OT Plus (OT/+) and OT Lite (OT/-) - the main difference is: if no (OT/+) handshake is sent back from the Slave to the master (after a control request from the master) the master goes into OT/- mode ie the Boiler is treated as dumb ....a simple on/off system that responds to heat requests from the Master OT.

              In OT/+ Mode: there is loads of monitoring/control data is passed back from the Slave to the Master eg Modulation (status is on/off) Return temp etc etc
              So confusing as this was what originally ideal said:

              The issues they have noticed are, target temp not being reached again due to cycling, overshoot of target temperature due to too high a flow temp and cycling & the boiler off dial not turning the boiler off. Boiler is behaving worse than a standard on off boiler.

              An example of this in my house is: House was sat at 20c at 7.30 this morning when set point was 22c, it had come on at 5am, flow temp was 45c and it was cycling on and off to get the rads hotter to 70c had to turn set point to 24c.

              Comment

              • blowlamp
                Automated Home Sr Member
                • Apr 2017
                • 98

                #97
                Originally posted by richardc1983 View Post
                Ideal have replied;

                I have spoken to our R&D team again on this query.

                From speaking to them it is apparent that Honeywell opentherm devices control both the flow temperature and the burner output, whereas most only operate the boilers flow temperature.

                This is causing the boiler operating mode to be overridden and hence the issue.

                I have again chased the PCB’s needed for your boiler today and am assured they will be with us very soon when I will be in touch again.

                Do you think Ideal might be referring to the way Honeywell OpenTherm devices operate at full burner output until they are within a degree or two of set temperature, at which point they then start to request a specific control flow temperature?

                Comment

                • dty
                  Automated Home Ninja
                  • Aug 2016
                  • 489

                  #98
                  Originally posted by Strat789 View Post
                  I looked at the OpenTherm Specification: the Master OT Plus (Opentherm Bridge, T6 and Evohome etc) can request control of the Slave (Boiler) Flow rates and the Set Temp. as required. There isn't anything in the Spec. about control of the Slave gas flow.
                  I believe all Evohome does is request the set temperature, but I can’t be certain. I have all the components to build an OpenTherm gateway, but haven’t found the time to do it yet. Once I do, I will know for certain.

                  If somebody could be bothered to cross-reference the message IDs, then this table would probably help: http://otgw.tclcode.com/matrix.cgi#thermostats

                  Comment

                  • richardc1983
                    Automated Home Sr Member
                    • Nov 2016
                    • 86

                    #99
                    Originally posted by blowlamp View Post
                    Do you think Ideal might be referring to the way Honeywell OpenTherm devices operate at full burner output until they are within a degree or two of set temperature, at which point they then start to request a specific control flow temperature?
                    Is this what it does? Hence constant cycling as boiler than can’t modulate quick enough.

                    Comment

                    • blowlamp
                      Automated Home Sr Member
                      • Apr 2017
                      • 98

                      Originally posted by richardc1983 View Post
                      Is this what it does? Hence constant cycling as boiler than can’t modulate quick enough.
                      I think the idea is to get the house nominally up to temperature as quickly as possible.
                      Does your system modulate properly once it's close to its setpoint?

                      Comment

                      • richardc1983
                        Automated Home Sr Member
                        • Nov 2016
                        • 86

                        It does modulate as I see a high flow temp when it first comes on, the issue at moment is it’s not modulating low enough and causes it to cycle off or overshoot.

                        Comment

                        • HenGus
                          Automated Home Legend
                          • May 2014
                          • 1001

                          Originally posted by blowlamp View Post
                          Do you think Ideal might be referring to the way Honeywell OpenTherm devices operate at full burner output until they are within a degree or two of set temperature, at which point they then start to request a specific control flow temperature?
                          That is not the way that the ATag appears to respond. With both CH and HW, the boiler TSet Calculated (flow) temperature rises slowly towards the TSet Max set in the boiler profile. Looking at the boiler manual, the temperature difference between flow and return guides the speed/gradient of the boiler temperature ramp up.

                          Once the TSet Calculated equals TSet Max, it stays there until all the zones are within a 2C range of their target temperatures. The boiler TSet Calculated temperature then reduces. For most of this afternoon, with all 12 zones at their target temperature, the boiler has operated in a flow/return range of 52 to 55C/ 40 to 45C. The only time that TSet Calculated rose was when my wife increased a zone temperature by 2C. It fell back within 10 to 15 minutes.

                          No short cycling here when TSet Calculated was close to TMax Set. I appreciate that we are not talking like for like here. Different boilers and different controls - albeit, both Opentherm.

                          Comment

                          • Dan_Robinson
                            Automated Home Ninja
                            • Jun 2012
                            • 347

                            The OpenTherm controller won't be able to affect the ramp rate of the burner.
                            Kind Regards - Dan Robinson (Jennings Heating Ltd)

                            Comment

                            • richardc1983
                              Automated Home Sr Member
                              • Nov 2016
                              • 86

                              Originally posted by Dan_Robinson View Post
                              The OpenTherm controller won't be able to affect the ramp rate of the burner.
                              Yeah I thought as much also, surely the boiler software is solely responsible for that.

                              My thoughts are that they have messed the boiler pcb up and are sorting it but not taking all the blame.

                              Comment

                              • Dan_Robinson
                                Automated Home Ninja
                                • Jun 2012
                                • 347

                                Precisely.

                                Boiler logic varies, and the ignition rate is also different and can affect micro loads if the burner is chucking out 7kW into a rad that can only take 500w.

                                Some boilers have return sensors, others do not. There are also all sorts of different heat exchanges, burners, fans etc.

                                As such there is no way a universal controller would/should have direct control over the gas side of the boiler. It can/should only have influence over the flow temperature. The better boilers too will have their own ability to limit flow temp - Intergas being one, Vaillant another, where Tmax can be limited in the boiler software.
                                Kind Regards - Dan Robinson (Jennings Heating Ltd)

                                Comment

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