Evohome & Opentherm

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  • mtmcgavock
    Automated Home Legend
    • Mar 2017
    • 507

    #16
    Originally posted by bruce_miranda View Post
    On the eBUS side there doesn't appear to be any indication of a difference between the two Heat Demands.
    Hence why I was surprised when @kevinsmart reported in another thread that the OT messages did infact differ. So I will check again.
    However I have implemented different temperatures for CH and HW in a roundabout way. I am monitoring the eBUS side and when I detect that Evohome is calling for HW, I vary the max on the Heating dial scale, that in turn raises or lowers the flow as required. It works extremely well. I can have CH flow set to 55C and then when there is HW demand, I set the flow to 70C.
    Vaillant by default only allows dual temperatures if you use their proprietary eBUS controls. But if you add that in, it overrides the VR33 because there is a eBUS hierarchy and the VR33 is lower than Vaillants own thermostat, that you need in order to use their HW kit.
    There's apparently a work around on the Plus System boilers - although i've never implemented it myself. How are you changing the set point using eBus? Some external device I assume.

    'Vaillant HW Priority on EcoTec Pluses

    The vaillant ecotec 6xx boiler can be used as a dual stat boiler.
    Use swithched live on terminal 4 for CH demand.
    Use a volt free contact to short the C1C2 plug on the harness (24V side) to take priority HW demand. Fit a Vaillant VR10 sensor to the orange and black wires of boiler harness to sense cylinder temperature.
    On the first gen ecotecs the temps are set with the dials. On the later models with DIA interface then HW temp is set in the diagnostic parameters.
    Never tried this with a VR33'

    Comment

    • bruce_miranda
      Automated Home Legend
      • Jul 2014
      • 2307

      #17
      That's the thing. I have an EcoTec Plus 438, it doesn't even have the 24V inputs on the PCB. Even to get OT to work, I had to play with the terminal 7-8-9, contrary to all advice in the manuals saying NOT TO BE USED in the UK!

      Comment

      • kevinsmart
        Automated Home Ninja
        • Sep 2018
        • 257

        #18
        Originally posted by bruce_miranda View Post
        On the eBUS side there doesn't appear to be any indication of a difference between the two Heat Demands.
        Hence why I was surprised when @kevinsmart reported in another thread that the OT messages did infact differ. So I will check again.
        However I have implemented different temperatures for CH and HW in a roundabout way. I am monitoring the eBUS side and when I detect that Evohome is calling for HW, I vary the max on the Heating dial scale, that in turn raises or lowers the flow as required. It works extremely well. I can have CH flow set to 55C and then when there is HW demand, I set the flow to 70C.
        Vaillant by default only allows dual temperatures if you use their proprietary eBUS controls. But if you add that in, it overrides the VR33 because there is a eBUS hierarchy and the VR33 is lower than Vaillants own thermostat, that you need in order to use their HW kit.
        I’ve got my new system up and running with my Vokera boiler and it looks like I was wrong, there is no distinction between CH and DHW demands coming from Evohome other than DHW is always max set point. Sorry!

        To workaround I am planning to install a relay to short circuit the outside sensor when the DHW BDR91 closes. From the OTGW I’ll then be able to distinguish, set 70C on DHW, and weather compensate on UFH.

        Comment

        • bruce_miranda
          Automated Home Legend
          • Jul 2014
          • 2307

          #19
          Using the max setpoint to determine that DHW is being called for won't give the desired outcome because often the CH demand is also set to the same max by the OTB for no good reason and that is when you definitely do not want to set a higher flow temperature.
          Detecting the DHW via the BDR91 is the sure way to do it and that is what I would have done too. But it was such an easy option for me to do this via software especially since I am constantly monitoring eBUS and Evohome.

          Comment

          • G4RHL
            Automated Home Legend
            • Jan 2015
            • 1580

            #20
            I am assuming this is the right section to ask this! If I install a Worcester Bosch 8000 Life Combi am I right assuming I need an adaptor to use Opentherm?

            Comment

            • G4RHL
              Automated Home Legend
              • Jan 2015
              • 1580

              #21
              Originally posted by G4RHL View Post
              I am assuming this is the right section to ask this! If I install a Worcester Bosch 8000 Life Combi am I right assuming I need an adaptor to use Opentherm?
              I can answer my own question. I asked it of Worcester Bosch and they replied to say Opentherm is not compatible with their boiler. They have their own system.

              The app for the Worcester Bosch control system which does more or less the same as Evohome is miles and miles ahead of the Evohome app for appearance and usability. It is like comparing a BBC Master computer with floppy discs to a present day desktop.

              Comment

              • G4RHL
                Automated Home Legend
                • Jan 2015
                • 1580

                #22
                Originally posted by G4RHL View Post
                I can answer my own question. I asked it of Worcester Bosch and they replied to say Opentherm is not compatible with their boiler. They have their own system.

                The app for the Worcester Bosch control system which does more or less the same as Evohome is miles and miles ahead of the Evohome app for appearance and usability. It is like comparing a BBC Master computer with floppy discs to a present day desktop.
                As an addendum to the post the Worcester Bosch installer who has quoted for the work, including adding my Evohome system to a new boiler, tells me Opentherm does work on a Worcester Bosch boiler! Who to believe? My understanding has been it does work but an interface is needed to make it so at a cost of about £34. I am sure somebody here will know the answer to this. Probably better than Worcester Bosch do!

                Comment

                • bruce_miranda
                  Automated Home Legend
                  • Jul 2014
                  • 2307

                  #23
                  Worcester Bosch and OpenTherm Worcester Bosch OpenTherm has eluded us here at MyBoiler.com for a while. New information has surfaced showing that it is indeed possible to use OpenTherm with a range…

                  Comment

                  • G4RHL
                    Automated Home Legend
                    • Jan 2015
                    • 1580

                    #24
                    Thanks, I was certain I had seen something about this somewhere.

                    Comment

                    • filbert
                      Automated Home Guru
                      • Oct 2017
                      • 161

                      #25
                      Reading various threads and reviews, I wonder if 'forcing' a Worcester-Bosch boiler to use Opentherm is worthwhile?

                      Comment

                      • G4RHL
                        Automated Home Legend
                        • Jan 2015
                        • 1580

                        #26
                        Originally posted by filbert View Post
                        Reading various threads and reviews, I wonder if 'forcing' a Worcester-Bosch boiler to use Opentherm is worthwhile?
                        I am inclined to agree. One would expect a manufacturer’s purpose designed system a better route to take than an add on converter to make it compatible with Opentherm. But then Evohome is good and works! Two other aspects are the WB system works in HomeKit, my wife likes the idea of asking Siri to change temperatures rather than using an app, and an approved WB installer is close at hand if things went wrong and she is in her own the Grim Reaper having taken me.

                        Comment

                        • G4RHL
                          Automated Home Legend
                          • Jan 2015
                          • 1580

                          #27
                          Since I started this post my replacement boiler decision has been made and I have elected for an Intergas combi as there is now one of their approved installers 10 miles away from me. I have read so much good about Intergas, here and elsewhere, it seemed it was becoming a no brainer. Will place the order for the boiler tomorrow plus the OpenTherm relay to replace my BDR91. It looks easy to install the OpenTherm wired into the designated points in the Intergas boiler it being configured for OpenTherm.

                          I have spent an age considering an electric, dry, system but affordability both with respect to capital cost and running cost ruled it out. Then it was boilers and my choice came down to Worcester Bosch and Intergas. The WB 8000 Life 35kW combi or initially the Intergas Xtreme 36kW combi. The Intergas boilers are cheaper than WB’s. Further digging sent me toward the Intergas Xclusive 36kW for the only differences between that and the Xtreme appear to be the price, the Xclusive is cheaper, and the Xtreme has a pre-heater of sorts for DMH. With WB I contacted them and they advised OpenTherm does not work with their boiler (I believe that is not correct but it does need an interface) plus they push their own smart system and if I went that route it’s another £600 approx to replace a perfectly good Evohome system.

                          The Intergas range in a way seems to be made with something like Evohome in mind. But as said I could not ignore the accolades Intergas has had for some years now. Even with a professional independent firm who advise on systems to install, but do not supply or install themselves, Intergas was one of only three boilers they would recommend. WB was not one of the other two. I believe the same firm has put the Intergas combi as top dog for 2021. But as said you can’t simply ignore what others have said in these pages! The installer I am using really enthused about Intergas having visited their factory with cynical mind 5 years ago, coming away convinced and impressed such that he installs them and prefers them to WB.

                          Let’s hope I am right!

                          I will have a redundant BDR91! Three in fact. The one that controls the CH at present, the DHW one and a spare that came with my T87RF thermostat some years ago and not needed. I should also have a better heated house. May keep she who must be obeyed happy!

                          Comment

                          • Bilbomacuser
                            Automated Home Jr Member
                            • Jan 2021
                            • 14

                            #28
                            Will be interested to hear how you get on. I’m still struggling to find anyone with experience of Evohome/Opentherm/Intergas and who also bothers to reply to emails... considering other brands now which is a shame because it does sound like evohome and Intergas are the perfect combination for someone who knows what they’re doing.

                            Comment

                            • G4RHL
                              Automated Home Legend
                              • Jan 2015
                              • 1580

                              #29
                              Originally posted by Bilbomacuser View Post
                              Will be interested to hear how you get on. I’m still struggling to find anyone with experience of Evohome/Opentherm/Intergas and who also bothers to reply to emails... considering other brands now which is a shame because it does sound like evohome and Intergas are the perfect combination for someone who knows what they’re doing.
                              My researches tell me that with OpenTherm the three work together but it is early days and also early days for the software upgrade Honeywell/Resideomare effecting to our Control Panels. However, even without OpenTherm my choice would have been Intergas.

                              Looking at the instructions adding the OpenTherm Bridge for the Intergas boiler seems to be no more than replacing the existing BDR91. Time will tell. I ought to learn from experiences that I should leave it all alone once installed and set up but often the temptation to play is great!
                              Last edited by G4RHL; 2 February 2021, 09:55 AM.

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