Evohome. Moving to opentherm S plan setup with Ideal Vogue

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  • Felkin123
    Automated Home Jr Member
    • Dec 2015
    • 26

    Evohome. Moving to opentherm S plan setup with Ideal Vogue

    Hi Everyone.

    Had a good trawl here and over at the evohome shop. but think i need something spelling out for me. Im a GSR engineer so one of those who does the "basic" plumbing and gas work Im also trying to keep up with the smart technologies and fit them for customers, Ive fitted 3 evohome systems to combis with little or no issues and two lyric wired based opentherm systems to combis also with little issue. The first evohome was fitted to an old glow worm ultracom which was in my house at purchase. I have since removed the glow worm and fitted an ideal vogue s26 with unvented cylinder. I got this all working properly with EH (including a new hot water kit and BDR alongside the existing tank stat in series) along with my existing evohome heating kit by resetting and reconfiguring it using some instructions Richard had put up for someone else. The current config is 2x2 port zone valves and an ABV one for heating (all rads have HR92s) and one for hot water both operated by BDR 91s both of which then activate the switched live to the boiler as required So a standard S plan evohome config right ?

    So. If I want to use opentherm....., I purchase the bridge and replace the BDR which controls the heating 2 port valve. I then configure the opentherm bridge as a boiler control relay (as you would a combi) this is where I get stuck, how to wire this ? how does the DHW 230v 2port valve switch then tell the opentherm bridge using 24v to fire the vogue. i cant use switched live and 24V on the Vogue at the same time according to Ideal. Im sure this has been explained on these pages somewhere but maybe Im too snowblind to see it. is there a schematic available for this setup ?
  • HenGus
    Automated Home Legend
    • May 2014
    • 1001

    #2
    FWIW, and I am not a GSR engineer, my installer removed the CH motorised valve on my ‘S’ plan and replaced it with an inline open/motorised closed valve and ABV. HW is controlled by a BDR not Opentherm. When there is a HW demand, the HW BDR opens the associated motorised zone valve which, in turn, powers the CH valve to the closed position. Evotouch via the Opentherm bridge then demands a max flow temp of 90C which is limited by TMax Set (70C) in the boiler settings profile. When the cylinder reaches the HW kit set temperature, the HW BDR clicks off and the HW valve closes and the inline CH valve opens. It took my installer about 5 minutes to do the re-wire.

    You will have no doubt noted that boiler/Opentherm combinations do not all work in the same way. For example, under Opentherm control, the manual CH max temperature control on my boiler is inoperative. Some other boilers do not limit the 90C hot water demand etc

    Edit: My installer is listed on the site below. I believe that they have a forum for installers:

    http://www.ecotechnicians.co.uk
    Last edited by HenGus; 22 January 2018, 04:54 PM.

    Comment

    • Felkin123
      Automated Home Jr Member
      • Dec 2015
      • 26

      #3
      Cool thanks for the reply Hengus so when your water is on your heating is disabled ? Has your installer actually replaced your C/H motorised valve with a different motorised valve or wired it such that it powers to closed instead of open. If he replaced it do you know what valve he used ?

      Comment

      • Felkin123
        Automated Home Jr Member
        • Dec 2015
        • 26

        #4
        I’ve just engaged my brain into the theory here. so

        If evotouch is calling for heat in the rads it will fire the boiler via the OT bridge (boiler relay) If there is a call for HW and no call for heat at the rads the evotouch will open the DHW valve and also fire the boiler from the OT bridge. (With heating motorised valve removed) The mod which Hengus describes is to create water priority mode which would be beneficial if you didn’t have HR92s on all rads ?

        Is that right?
        Last edited by Felkin123; 22 January 2018, 06:57 PM.

        Comment

        • HenGus
          Automated Home Legend
          • May 2014
          • 1001

          #5
          My system is configured for hot water priority. When CH is in operation, as you know, no valve is actually needed if HR92s are fitted to all radiators. The CH valve that closes when the HW zone valve opens is a Honeywell V4043B1257.

          Comment

          • Felkin123
            Automated Home Jr Member
            • Dec 2015
            • 26

            #6
            Originally posted by HenGus View Post
            My system is configured for hot water priority. When CH is in operation, as you know, no valve is actually needed if HR92s are fitted to all radiators. The CH valve that closes when the HW zone valve opens is a Honeywell V4043B1257.
            The 4043B is a normally open valve instead of a 4043H which is a normally closed. That’s a good mod ! I’m debating whether to take the plunge and buy the bridge. It’s not so much that I particularly want OT functionality more that I want to guinea pig it on my own system before I fit it on a customers 😀 I’ve has an issue with a Lyric and opentherm on a customers combi and it’s embarrassing as an engineer. ‘It should work’ doesn’t really cut it when your reputation is in question. I’m trying really hard NOT to be one of those ‘don’t touch Opentherm ‘ engineers

            Comment

            • HenGus
              Automated Home Legend
              • May 2014
              • 1001

              #7
              One of the ‘benefits’ of the Bridge is that it can be sited well away from all the other Evohome components. When I had Evohome installed nearly 4 years ago, I had months of BDR comms issues even though the 300mm separation was in place. My Bridge sits is in the corner of an integral garage well away from the controller and the hot water BDR.

              Comment

              • mtmcgavock
                Automated Home Legend
                • Mar 2017
                • 507

                #8
                Originally posted by Felkin123 View Post
                The 4043B is a normally open valve instead of a 4043H which is a normally closed. That’s a good mod ! I’m debating whether to take the plunge and buy the bridge. It’s not so much that I particularly want OT functionality more that I want to guinea pig it on my own system before I fit it on a customers �� I’ve has an issue with a Lyric and opentherm on a customers combi and it’s embarrassing as an engineer. ‘It should work’ doesn’t really cut it when your reputation is in question. I’m trying really hard NOT to be one of those ‘don’t touch Opentherm ‘ engineers
                You can also wire Hot Water Priority without needing a 4043B and use a standard valve, you just configure the wiring differently. I have a switch on mine that I can turn HW priority on or off as I see fit.

                The easiest way in your situation would be to leave the BDR91s as they are, controlling the valves, purchase a Opentherm relay and add it to the boiler. Bind as a Opentherm Boiler Control in EvoHome and disconnect the S/L to the boiler and Grey/Orange wires from the MVs. If you want to remove your heating MV at a later date you can do.

                Comment

                • Felkin123
                  Automated Home Jr Member
                  • Dec 2015
                  • 26

                  #9
                  So would wiring it as hot water priority ensure that the boiler goes to maximum for HW duties ? If not I don’t think there would be much point on my system

                  Comment

                  • mtmcgavock
                    Automated Home Legend
                    • Mar 2017
                    • 507

                    #10
                    Originally posted by Felkin123 View Post
                    So would wiring it as hot water priority ensure that the boiler goes to maximum for HW duties ? If not I don’t think there would be much point on my system
                    The EvoHome is meant to tell the Opentherm relay to go into maximum flow temperature to allow hot water to reheat, however I think different people have experience different outcomes on different brands of boilers. I'm unsure what Ideal is like, however I remember a following forum member having a lot of trouble with his Ideal Vogue and opentherm with the Lyric.

                    However there's sometimes when I don't think HW priority is the best solution, that's why I have the ability to easily turn mine on or off.

                    Comment

                    • dty
                      Automated Home Ninja
                      • Aug 2016
                      • 489

                      #11
                      Starting from where you are now, the easiest thing to do is buy the OT Bridge, connect it to your boiler, disconnect the orange switched lives from the valves, and configure Evohome with OpenTherm boiler control. The valves will continue to open/close as appropriate. You can enhance this with HW priority - but that’s literally just a valve wiring setup to ensure that if the HW valve is open then the CH valve is closed. The primary advantage of doing this is that when Evohome wants to heat the hot water it will request 90C via OpenTherm. Having hot water priority prevents this very hot water circulating around the radiators and causing overshoots. As someone else said, different boilers react in different ways when asked for 90C over the OpenTherm interface. My Vaillant continues to obey the max flow temperature configured in the installer menu. Others don’t! I assume your boiler supports (or can support) OpenTherm.

                      Comment

                      • Felkin123
                        Automated Home Jr Member
                        • Dec 2015
                        • 26

                        #12
                        Oh yes the vogue supports OT in fact one of the ideal tech guys who did my installer course told me that Honeywell write the code for Ideals PCBs. The highest set point is still governed by manual input on the boilers dial. I currently have this set to 70 degrees. Presumably if I didn’t have hot water priority wired in but have HR 92s on all rads then the overshoot won’t be a problem. Although do I then run the risk of OT modulating the flow temperature down before the water in the UV is hot ? I’m thinking of removing my heating valve entirely as it’s noisy and right outside a bedroom. I was also thinking of moving my ABV to under the living room floor as that also makes a lot of noise. (I have a void beneath my living room accessible by a door )

                        Comment

                        • dty
                          Automated Home Ninja
                          • Aug 2016
                          • 489

                          #13
                          No, OT will call for 90C until the tank is up to temperature. However, the boiler may modulate down depending on how much heat is being extracted towards the end of the process (lower dT = lower heat transfer = higher return temps = lower boiler power required). Having HR92 on all radiators won’t prevent overshoots. Imagine that the house is just ticking over nicely with a 50C flow when the hot water kicks in. Suddenly, you have much hotter water (typically 70C or 75C limited by the boiler) rushing around the system and via the radiators which were nicely set up to maintain temperature with a 50C flow. That said, that’s the setup I have and it never a major issue. Plus, having no CH valve at all (also my setup) is Honeywell’s recommended configuration.

                          Comment

                          • Felkin123
                            Automated Home Jr Member
                            • Dec 2015
                            • 26

                            #14
                            Ah of course that makes sense re overshoots. I think I’ll set it up without the heating valve to start with and see how I get on. I’ll drain down the whole system anyway as there’s a few other bits I want to do while it’s drained. Loads of help from you folks here thanks a lot. I’ll order the bridge from Richard and I’ll let you know how I get on.

                            Comment

                            • Felkin123
                              Automated Home Jr Member
                              • Dec 2015
                              • 26

                              #15
                              Re hot water priority on existing zone valve what is the modification to make it reverse its open/close functionality. I.e what swaps with what ?

                              Comment

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