OpenTherm VR33 and Vaillant ecoTEC plus 428

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  • Vikings
    Automated Home Sr Member
    • Jan 2021
    • 55

    OpenTherm VR33 and Vaillant ecoTEC plus 428

    I have a Vaillant ecoTEC plus 428 boiler and I'd like to use OpenTherm to control the temperature. I have purchased a VR33 module but wanted to check if anyone had successfully used this with my particular model of boiler. Does anyone know if it is compatible?
    I'm aware of the warranty issues but my boiler is out of it's 5 year period now. I also understand there are concerns about self-install and that I'd need to get a qualified person to install or at least test my installation.
  • bruce_miranda
    Automated Home Legend
    • Jul 2014
    • 2307

    #2
    I have a 438 and have used the VR33 for many years now. The 428 is very similar.
    I might have been the guy that determined how, it could be connected to the 438 because the instructions floating around at the time did not appear to relate to my boiler. It's particularly scary when you are making connections on a terminal block on the boiler PCB, which is clearly marked, DO NOT USE in the UK!

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    • Vikings
      Automated Home Sr Member
      • Jan 2021
      • 55

      #3
      That's very helpful - thanks. I was a bit unsure as the VR33 manual shows the cable plugging into a connector marked X32 on the side of the board whereas the board in my boiler has X31 at the end of the board and a different X32 connector near the middle of the board. It also doesn't have any mounting slot to put the VR33 in (although there is plenty of space so less of an issue).boiler-pcb-snip.jpg

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      • bruce_miranda
        Automated Home Legend
        • Jul 2014
        • 2307

        #4
        I used that space on the side, it's got a nice plastic upstand separation from the PCB.

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        • bruce_miranda
          Automated Home Legend
          • Jul 2014
          • 2307

          #5
          If you do not work this out based on the threads I made on this forum, let me know. I can click a photo of my boiler set up. Especially the 230V 3-4 jumper and the jumper that needs to goes in on the 7--8-9 slots.
          When you plug in the module, you can check if the boiler has recognised the module by looking up the eBUS setting. Then you can also work out if the target temperature is being set correctly or not, even without the OTB connected. If you put the jumper on the VR33 the target should be 90C, if you remove it should be 10C

          p.s. I had a picture in my archives.
          Jumper between 3-4, 7-8 and module connected to X31. See location of module housed.
          Attached Files
          Last edited by bruce_miranda; 10 March 2021, 01:59 PM.

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          • Vikings
            Automated Home Sr Member
            • Jan 2021
            • 55

            #6
            That's excellent - thanks again. Was there a reason the boiler wiring plug is not in its socket in the photo? I'm guessing that's normally plugged in when in use.

            So I'm assuming the jumpers provide the 'demand' to the boiler on a permanent basis. One thing I wondered about was would this mean the heating pump is running 24/7 with the VR33 just controlling the temperature or does the boiler work out whether it can stop circulating in certain situations?

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            • bruce_miranda
              Automated Home Legend
              • Jul 2014
              • 2307

              #7
              Ignore that. This photo was actually taken as part of a PCB swap, rather than the VR33 install.

              Comment

              • bruce_miranda
                Automated Home Legend
                • Jul 2014
                • 2307

                #8
                OT provides a setpoint of 10C, which the boiler considers as OFF and then starts the Pump over run timer from that point on and then the Pump switches off.

                Comment

                • Vikings
                  Automated Home Sr Member
                  • Jan 2021
                  • 55

                  #9
                  That's a relief - I had visions of hearing it running all night. Thanks for clarifying.

                  Comment

                  • bruce_miranda
                    Automated Home Legend
                    • Jul 2014
                    • 2307

                    #10
                    If you have any eBUS Thermostats or the additional boiler controller that is plugged into the boiler faceplate, then those need to come out. The VR33 has quite a low priority in the eBUS hierarchy, so it is rendered useless if you have other competing controllers on the BUS.

                    Comment

                    • Vikings
                      Automated Home Sr Member
                      • Jan 2021
                      • 55

                      #11
                      I have nothing connected to the eBUS. What do you mean by 'additional boiler controller'?
                      My existing system (Y-plan) just controls the demand signal into terminal 4 on the boiler board - which I believe you are saying will need to be permanently looped ON.

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                      • bruce_miranda
                        Automated Home Legend
                        • Jul 2014
                        • 2307

                        #12
                        If you look at your boiler, it comes with a blank face plate. Some installations replace that face plate with a controller for things like scheduling etc. Most don't have it.

                        Comment

                        • Vikings
                          Automated Home Sr Member
                          • Jan 2021
                          • 55

                          #13
                          I see. I'm pretty sure there is nothing 'non-standard' there. Here's a picture of the front panel.boiler-frontpanel-snip.jpg

                          Comment

                          • bruce_miranda
                            Automated Home Legend
                            • Jul 2014
                            • 2307

                            #14
                            You see that plate with Vaillant printed on it, that is removable and it can be replaced with a controller. You don't have it.

                            Comment

                            • Vikings
                              Automated Home Sr Member
                              • Jan 2021
                              • 55

                              #15
                              Excellent - thanks. Sounds like I'm pretty much set.

                              Comment

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