Troubleshooting opentherm on a vailant boiler with VR33

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  • dbrb2
    Automated Home Jr Member
    • Sep 2017
    • 11

    Troubleshooting opentherm on a vailant boiler with VR33

    I have a Vailant boiler (ecoTec pro 24) with a VR33 ebus<>opentherm converter.

    All seems OK...when the opentherm gateway is disconnected, the VR33 LED is solid green
    When the gateway is connected, the LED flashes green

    However, the boiler won't respond to opentherm commands. Any ideas....?
  • bruce_miranda
    Automated Home Legend
    • Jul 2014
    • 2307

    #2
    can you describe the steps you took to install. Also what is happening to make you think the boiler is not responding to the OT commands. Have you see my OT connection posts.

    Comment

    • dbrb2
      Automated Home Jr Member
      • Sep 2017
      • 11

      #3
      Ok - steps:

      The boiler is a Vailant ecoTec Pro 24
      Was connected to a 230v thermostat
      230v thermostat removed, VR33 module installed
      VR33 connected to X31 on main PCB
      VR33 receives power from main PCB

      When openTherm gateway (nest Heatlink) is powered up bot NOT connected to the VR33m, it complains than openTherm is not connected. When connected, this error vanishes - suggesting valid comms between the VR33 module and the Heatlink
      However, none of the test functions on the heatlink seem to cause the boiler to fire up

      This led me to suspect comms from heatlink to VR33 were OK, but the eBus link from VR33 to main PCB was an ieeus

      IMG_20171119_180245.jpg

      There seems to be some confusion as to whether terminals 3/4 need to be bridged in order to use eBus...?

      Comment

      • bruce_miranda
        Automated Home Legend
        • Jul 2014
        • 2307

        #4
        You are missing the links on terminal between 3 and 4 and between 7 and 8. Whenever you use an eBus controller you need to link 3-4 and because you are using the VR33 you also need to link the 24RT which is missing on your PCB, the equivalent link is 7-8.

        Check the D.90 to make sure the VR33 is detected by the boiler.
        Then using just the jump link that came in the box of the VR33, check that the D.9 jumps from 10C with the jumper off and boiler not firing to 90C with the jumper on and the boiler firing.
        Last edited by bruce_miranda; 19 November 2017, 07:21 PM.

        Comment

        • dbrb2
          Automated Home Jr Member
          • Sep 2017
          • 11

          #5
          Ah - that seems to have done it! I couldn't find any manuals showing my PCB - maybe it's an older model?
          With those links in, all seems fine and D.90 shows "1"

          I'll keep an eye on things, but looking good...

          Out of interest, do you know the relationship between OT issues demand temperatures and locally set ones via the boiler rotary dials?

          By experimentation, if I set both dials to 30 degrees, the boiler will not heat above this temperature - so I guess they set a maximum....but what if OT requests a lower temperature...?

          Comment

          • dty
            Automated Home Ninja
            • Aug 2016
            • 489

            #6
            I don't have your exact model of boiler, but I have a different Vaillant with OpenTherm. The controls should set the maximum temperature, and allow for a lower temperature if requested from Evohome. Basically, it works exactly as you'd expect... unlike some other boilers!

            Comment

            • bruce_miranda
              Automated Home Legend
              • Jul 2014
              • 2307

              #7
              There were no manuals. I had to figure that out myself.

              Comment

              • HenGus
                Automated Home Legend
                • May 2014
                • 1001

                #8
                Originally posted by dbrb2 View Post

                Out of interest, do you know the relationship between OT issues demand temperatures and locally set ones via the boiler rotary dials?
                As many have noted, the OT protocol is open to interpretation. On my ATag boiler, manual boiler settings are ignored. When OT demands maximum heat for CH, then the flow temperature limit is what is set in the boiler's profile. My boiler profile is limited to a TSet Max of 70C. OT will then calculate a TSet temperature depending on the total CH demand. For example, at the moment, my boiler is running at a TSet flow temperature of 54C. When there is no CH demand, TSet falls back to 20C.

                Comment

                • bruce_miranda
                  Automated Home Legend
                  • Jul 2014
                  • 2307

                  #9
                  The fact that the OT bridge is respecting your TSet Max set on the boiler means that your boiler controls are still operational. Thank goodness you don't have a Viesmann which ignores every boiler setting and tries to get to 90C because the OT bridge is demanding that...yikes imagine touching a rad with 80C+ water flowing through it.

                  Comment

                  • HenGus
                    Automated Home Legend
                    • May 2014
                    • 1001

                    #10
                    Originally posted by bruce_miranda View Post
                    The fact that the OT bridge is respecting your TSet Max set on the boiler means that your boiler controls are still operational. Thank goodness you don't have a Viesmann which ignores every boiler setting and tries to get to 90C because the OT bridge is demanding that...yikes imagine touching a rad with 80C+ water flowing through it.
                    I am not disputing that. All I am saying is that the manual CH flow control on my boiler is effectively inoperative. It appears to work - ie, it will let me set a max flow temperature - but OT just ignores it. This sort of makes sense. If the key benefit of OT control is a calculated max flow temperature then why allow the user to fiddle with it. That said, the P0 (max CH TSet temperature) can be varied in the range 50 to 80C via the installer settings. However, part of the installation set up process is to set the correct profile for the boiler and property.

                    Comment

                    • Dan_Robinson
                      Automated Home Ninja
                      • Jun 2012
                      • 347

                      #11
                      Originally posted by bruce_miranda View Post
                      yikes imagine touching a rad with 80C+ water flowing through it.
                      Millions of people have been doing so since the invention of central heating.
                      Kind Regards - Dan Robinson (Jennings Heating Ltd)

                      Comment

                      • DBMandrake
                        Automated Home Legend
                        • Sep 2014
                        • 2361

                        #12
                        Originally posted by Dan_Robinson View Post
                        Millions of people have been doing so since the invention of central heating.
                        You soon learn not to touch it.

                        Comment

                        • HenGus
                          Automated Home Legend
                          • May 2014
                          • 1001

                          #13
                          When I was a child, I was taught by my parents not to touch hot things by being made to touch something hot. I imagine that would be deemed child cruelty today.

                          Comment

                          • Dan_Robinson
                            Automated Home Ninja
                            • Jun 2012
                            • 347

                            #14
                            First thing my son learnt in both languages was "hot".

                            Set up the log burner at my dad's and let him touch it (before it got hot hot obviously). Telling him it was hot, but not stopping him.

                            He soon learnt that lesson.

                            Easier than potty training for number 2's anyway.
                            Kind Regards - Dan Robinson (Jennings Heating Ltd)

                            Comment

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