Evohome + Opentherm v Evohome + Boiler Outside Weather Compensation

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  • bruce_miranda
    Automated Home Legend
    • Jul 2014
    • 2307

    Originally posted by StuartG View Post
    I have a Vaillant 637 system boiler running with the VR33 and OpenTherm bridge.

    In my case I removed the existing 230V connection that was wired to the BDR91. I connected the VR33 to the expansion board on the side (for me, X31). I also had to reinstate a jumper on the 24V RT connection (for me this was X100, coloured white, and labelled RT24). The boiler installation instructions explicitly say to REMOVE that jumper when using 230V controls. There was a handy little piece of wire in the VR33 box that did just the job. The VR33 instruction (assuming I read the Dutch properly!) don't seem to specifically point this out, presumably because the module could go in various boilers. The installation manual my boiler does say that RT24 might also be labelled X106.

    I too get a confirmation on diagnostic code 90, so it sounds like the module has been recognised.

    I don't know the specifics of how the wiring works inside the boiler, but I am guessing that in the absence of the RT24 jumper then the circuit is broken and hence the boiler never fires up? My understanding is that shorting the OpenTherm connection itself should cause the boiler to fire.

    Hope this helps!
    I too think it's something to do with the 24V connection, but on my boiler it's not marked as such. There are 24V connections called 7 8 9 but the UK never had any controls that used those. There are some boilers that had to switch a diagnostic code (d.20) to switch the boiler from On/Off to Opentherm. But again nothing on that for me.
    My entire installation and all the signs seem to suggest that my OpenTherm module VR33 is installed correctly and is talking nicely to the boiler. No error codes and all the lights are flashing as they should.

    I feel I am close, but yet very far!
    Last edited by bruce_miranda; 10 April 2016, 10:16 PM.

    Comment

    • bruce_miranda
      Automated Home Legend
      • Jul 2014
      • 2307

      Can either Stuart or top brake tell me if they can see the target temperature changing on D.009 and also what does D.016 show currently with your 24V RT bridge in place and the VR33 installed? Does D.016 change when there is heat demand or not?

      Comment

      • StuartG
        Automated Home Jr Member
        • Mar 2015
        • 45

        D.009 does indeed vary. I've seen values varying from low 50s to 90C since it's been installed. High values when house is cold / heating up; low values when we're at target and maintaining, which seems logical.

        D016 shows 24V DC Heat Mode: On.

        Comment

        • bruce_miranda
          Automated Home Legend
          • Jul 2014
          • 2307

          And what does D.008 show?

          Comment

          • StuartG
            Automated Home Jr Member
            • Mar 2015
            • 45

            Controller 3-4 0:Open

            Comment

            • bruce_miranda
              Automated Home Legend
              • Jul 2014
              • 2307

              How do you guys know if the Opentherm bridge is calling for heat or not? On the bdr91 its dead easy.

              Comment

              • StuartG
                Automated Home Jr Member
                • Mar 2015
                • 45

                I've not actually looked to see what input indicates that the bridge is calling for heat, other than the boiler fires up! Sorry!

                Comment

                • bruce_miranda
                  Automated Home Legend
                  • Jul 2014
                  • 2307

                  Would you be able to? Just want to know if my Opentherm bridge is calling for heat or not? If I know how i can be sure it is calling for heat then I can move on to working out why the boiler isnt responding or ignoring that command.

                  Having read (too) many manuals last night it seems that eBUS modules are registered automatically and the boiler 'knows' that it has to listen to them. But its not doing that with my VR33 even though the boiler recognised it as an eBUS device.
                  So either the VR33 is issuing eBUS commands that my boiler cant understand or I need to bridge something else (similar to what the 24V RT) is.

                  If only there was a way to look at the eBUS traffic on the boiler. There is an eBUS diagnostic port on the boiler.

                  Comment

                  • bruce_miranda
                    Automated Home Legend
                    • Jul 2014
                    • 2307

                    Are any of you using the VR65 or VR66 wiring centre?
                    According to Vaillant you will need a wiring centre to use ebus controls with the 400 and 600 series’ ecoTEC boilers.

                    I dont have this. I simply have a 230v Honeywell S plan wiring box.

                    Comment

                    • StuartG
                      Automated Home Jr Member
                      • Mar 2015
                      • 45

                      No - everything was originally wired using a standard Salus wiring centre. When I reconfigured it to use OpenTherm it was just a case of disconnecting the boiler relay BDR91 and putting the OpenTherm bridge in its place.

                      Comment

                      • bruce_miranda
                        Automated Home Legend
                        • Jul 2014
                        • 2307

                        I have got this to now work in a "Hybrid" set-up.

                        For some reason my boiler, a Vaillant ecoTec Plus 438 open vented, won't fire up simply via eBUS issued by the VR33 (assuming it is issuing that command). I use the term eBUS because the VR33 is nothing but an OpenTherm to eBUS converter. However the VR33 does seem to be talking to the boiler. When I install the VR33 module I can see the boiler d.90 change from 0 (eBUS unidentified) to 1 (eBUS identified). Also when I remove the OT jumper on the VR33 module the target temperature as seen in d.09 goes down to 10C. When I put in the jumper the d.09 jumps to 70C, which is what I have set the maximum temperature to be on the boiler knob.

                        When I connect the Evohome Opentherm bridge the d.09 changes based on heat demand. Values I saw were 90 when there is HW demand, 53 when there is normal CH demand, 74 when there is a lot of CH demand, 40 when there is low CH demand. Pressing the Evohome Opentherm bridge button toggles the target between 90 (on and full) to 10 (off).

                        So I knew the heat modulation was working between Evohome and the boiler. But I still couldn't fire the boiler up when there was demand.

                        Luckily I had not changed the old zone valve wiring and that was still in place. So I connected the 230V heat demand wire back to terminal 4 on the boiler (as it would have been in a normal 230V S plan set-up).

                        So now the actual boiler firing is triggered via the old S plan wiring (micro switches in the motorised zone valves) and the various BDR91 controlling the motorised valves themselves. But the target temperature to get to is set by the OpenTherm bridge.

                        It all seems to work just fine and didn't cost me any more. All the original safety features are still intact and I didn't need to change the wiring a lot. Infact even to move to using two BDR91 to control the motorised valves, I simply swapped the old honeywell timer to two BDR91, one for HW and the other for CH.

                        I'll report back in a little while how things are looking but a massive thanks to top brake, StuartG, Paul and Richard for getting me this far.

                        I guess if I wanted a complete eBUS boiler firing then I'd need to invest in a Vaillant wiring centre but for the moment I cannot see the need to do so. The main aim for me going down the Opentherm route was to get the boiler to modulate based on demand, and I think that purpose has been satisfied.

                        P.S. I'd be very keen to know how StuartG's boiler works completely on eBUS when Vaillant themselves insist that the wiring centre is required. I'll put this down to the age of the boilers and mine having some kind of the limitation to only talk eBUS via the wiring centre.
                        Last edited by bruce_miranda; 11 April 2016, 01:46 PM.

                        Comment

                        • top brake
                          Automated Home Legend
                          • Feb 2015
                          • 837

                          Originally posted by bruce_miranda View Post
                          Are any of you using the VR65 or VR66 wiring centre?
                          According to Vaillant you will need a wiring centre to use ebus controls with the 400 and 600 series’ ecoTEC boilers.

                          I dont have this. I simply have a 230v Honeywell S plan wiring box.
                          no i do not have vr65 or vr66
                          I work for Resideo, posts are personal and my own views.

                          Comment

                          • paulockenden
                            Automated Home Legend
                            • Apr 2015
                            • 1719

                            Have you tried bridging terminals 3 and 4 (which I think should force the boiler to 'on')? Is the opentherm stuff then able to switch it off when not needed?

                            P.

                            Comment

                            • jdp80
                              Automated Home Jr Member
                              • Mar 2016
                              • 38

                              You can buy an ebus to usb converter and query the boiler from a Raspberry PI or similar using ebusd - I am using it to monitor flow/return etc.

                              Comment

                              • pixxelbob
                                Automated Home Lurker
                                • Apr 2016
                                • 6

                                I've been following this thread closely.
                                I have a brand new 2016 ecoTec Plus 835 ErP

                                Despite Vaillant telling me & my installer it will never work.
                                We followed the quite frankly simple steps, you very helpful people have provided here.
                                We installed the VR33, bound the wireless bridge it really was as simple as that.

                                * Remove 240v thermostat wires
                                * Install module, plug in cable from X31 on mainboard to X32 on module.
                                * Bridge burner off
                                * Bridge RT24
                                * Wire from OT T to Wireless bridge
                                * Turn everything on & bind

                                I've read people have issues binding modules & valves but I got everything bound first time.

                                Here it is working. I guess we'll see how it performs over the coming weeks/months.
                                Thanks to all who contributed to this thread

                                2016-04-11 23.24.16.jpg
                                2016-04-10 22.08.37.jpg
                                Last edited by pixxelbob; 12 April 2016, 12:18 AM.

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