Honeywell evohome and OpenTherm integration

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  • top brake
    Automated Home Legend
    • Feb 2015
    • 837

    Honeywell evohome and OpenTherm integration

    Honeywell evohome is unique in the market in offering multizone control of radiator, zone valves and underfloor heating manifold applications
    This application capability meets the definitions of ErP Class VIII for multizoning of modulating heaters
    The OpenTherm Bridge R8810A1018 enables full modulation control of OpenTherm appliances


    Starting a new thread to capture your feedback and to enable any specific cases to be followed up with official Honeywell Tech Support teams as appropriate

    If you have any application related questions pre sale or post sale post them here so we can answer on a case by case basis and collate the answers for others to benefit from
    I work for Resideo, posts are personal and my own views.
  • HenGus
    Automated Home Legend
    • May 2014
    • 1001

    #2
    Thanks TB. As suggested by @Rameses, I have raised a case (15186093) via your Technical Support site. My concern - based on just three weeks of heating in April - was the time taken for Evohome/OT to get the boiler into condensing mode. There were only a few zones on and most were at, or close to, their target temperatures, yet the boiler was still showing a flow return temperature of 65+C for a considerable amount of time before starting to fall back. The boiler, an Atag IS24, is set to HW priority and HW was OFF when CH was being demanded. I thought that the idea of OT was to modulate the gas valve to a minimum consistent with keeping set zone temperatures?
    Last edited by HenGus; 27 July 2017, 05:29 PM.

    Comment

    • paulockenden
      Automated Home Legend
      • Apr 2015
      • 1719

      #3
      Can the Honeywell guys confirm whether or not, with OpenTherm, the system still only starts to ramp down demands when all zones are within 1.5 degrees of their setpoint?

      Or does OpenTherm make the proportional band a bit wider, which would seem sensible?

      P.

      Comment

      • top brake
        Automated Home Legend
        • Feb 2015
        • 837

        #4
        Originally posted by HenGus View Post
        Thanks TB. As suggested by @Rameses, I have raised a case (15186093) via your Technical Support site. My concern - based on just three weeks of heating in April - was the time taken for Evohome/OT to get the boiler into condensing mode. There were only a few zones on and most were at, or close to, their target temperatures, yet the boiler was still showing a flow return temperature of 65+C for a considerable amount of time before starting to fall back. The boiler, an Atag IS24, is set to HW priority and HW was OFF when CH was being demanded. I thought that the idea of OT was to modulate the gas valve to a minimum consistent with keeping set zone temperatures?
        Thanks will look into the case and revert
        I work for Resideo, posts are personal and my own views.

        Comment

        • top brake
          Automated Home Legend
          • Feb 2015
          • 837

          #5
          Originally posted by paulockenden View Post
          Can the Honeywell guys confirm whether or not, with OpenTherm, the system still only starts to ramp down demands when all zones are within 1.5 degrees of their setpoint?

          Or does OpenTherm make the proportional band a bit wider, which would seem sensible?

          P.
          The control logic is at the evohome controller and either controls the boiler output using the TPI cycle rate/run time or the required flow temp through OT.
          This the aggregated demand of all zones.

          In either case outside the Proportional Band the boiler demand will be at full rate.

          In the case of multizoning the individual HR92 or zone valves or thermal actuators will control the local zone temperatures.

          HTH
          I work for Resideo, posts are personal and my own views.

          Comment

          • paulockenden
            Automated Home Legend
            • Apr 2015
            • 1719

            #6
            I don't think that really answers the question of whether the proportional band remains at 1.5 degrees when under OpenTherm control, or widens a bit to allow the boiler to modulate down.

            Comment

            • top brake
              Automated Home Legend
              • Feb 2015
              • 837

              #7
              proportional band width is non adjustable and optimised for the application, heating systems are slow reacting so a 1.5 degree control band is fine
              The mass flow to the respective zones is modulated locally

              The heat demand is aggregated and throttled accordingly

              The self learning fuzzy logic control algorithm is the same whether switching a BDR or modulating flow temperatures through OT

              It is the steady state control performance and low load operation that is key to achieving maximum condensing effficiency. If the hydronic system is imbalanced or the boiler oversized it will be difficult to achieve thermal equilibrium and sufficient delta T to ensure return temperatures are below 55degC

              With a correctly specified and commissioned modulation control system you should see flow temperatures around 45 to 50 degC. My evohome with Vaillant ecotec system at home achieves this easily.
              Last edited by top brake; 27 July 2017, 07:12 PM.
              I work for Resideo, posts are personal and my own views.

              Comment

              • StephenC
                Automated Home Guru
                • Feb 2017
                • 102

                #8
                Several questions from me:

                1. Why does EvoHome not (at present) have a max CH water temp config setting when connected to the R8810 OT bridge?

                2. Will point 1 above capability ever be added? I can't add R8810 OT bridge back into my system until this is resolved.

                3. From my experience, EvoHome asks for max ch temp or very very low (25-30 degrees C), I very rarely saw anything in the middle.This is like a cliff edge, so why when within 1.5 degrees C does it not ramp down the temperature gradually to avoid the possibility of overshoots and allow for the HR92 time for finer control?

                4. Data. When will we be able to see the data (somehow, somewhere - in the app maybe?) showing what the system is doing and when? It's very difficult to troubleshoot blind.

                For history of my issues with a Viessmann Vitodens 111-W boiler that when EvoHome asks for full rate - that means upwards of 80+ degrees C.....right up to the set point and then ramps down too late, see here:



                Thanks.

                Stephen

                Comment

                • top brake
                  Automated Home Legend
                  • Feb 2015
                  • 837

                  #9
                  Originally posted by StephenC View Post
                  Several questions from me:

                  1. Why does EvoHome not (at present) have a max CH water temp config setting when connected to the R8810 OT bridge?

                  2. Will point 1 above capability ever be added? I can't add R8810 OT bridge back into my system until this is resolved.

                  3. From my experience, EvoHome asks for max ch temp or very very low (25-30 degrees C), I very rarely saw anything in the middle.This is like a cliff edge, so why when within 1.5 degrees C does it not ramp down the temperature gradually to avoid the possibility of overshoots and allow for the HR92 time for finer control?

                  4. Data. When will we be able to see the data (somehow, somewhere - in the app maybe?) showing what the system is doing and when? It's very difficult to troubleshoot blind.

                  For history of my issues with a Viessmann Vitodens 111-W boiler that when EvoHome asks for full rate - that means upwards of 80+ degrees C.....right up to the set point and then ramps down too late, see here:



                  Thanks.

                  Stephen

                  Hi Stephen

                  1 - this is not a requirement of the OpenTherm protocol specification
                  2 - no plans
                  3 - see 5 below
                  4 - yes there is a third party OT monitor that alllows this monitoring
                  5 - the history of your case is long and complex and i recall you having on site support and support from theevohomeshop?
                  I work for Resideo, posts are personal and my own views.

                  Comment

                  • StephenC
                    Automated Home Guru
                    • Feb 2017
                    • 102

                    #10
                    Hi,

                    Thanks for the confirmation of point 2.

                    I shall look at alternatives to OpenTherm (at reducing gas usage and therefore on-going cost saving and emissions savings) at this point now I know.

                    Re: theevohomeshop - no I worked with my local installer (and seem to be teaching him on this...). No on site support from HoneyWell, but I did have support over the phone from one of your colleagues and they setup data logging etc.


                    Stephen

                    Comment

                    • The EVOHOME Shop
                      Site Sponsor
                      • Dec 2014
                      • 483

                      #11
                      Originally posted by StephenC View Post
                      Hi,

                      Thanks for the confirmation of point 2.

                      I shall look at alternatives to OpenTherm (at reducing gas usage and therefore on-going cost saving and emissions savings) at this point now I know.

                      Re: theevohomeshop - no I worked with my local installer (and seem to be teaching him on this...). No on site support from HoneyWell, but I did have support over the phone from one of your colleagues and they setup data logging etc.


                      Stephen
                      Hi Stephen,

                      Can you clarify why a Tmax setpoint is required from the controls?

                      The Intergas boiler I have at our training centre has the ability to set this manually (I designed our system with a 70 degree flow temp, so have limited it to this), but I understand that your Viessmann doesn't?

                      Most heating systems have a 75 degree flow temperature design point and I would imagine that once evohome is over its initial 'learning' phase, Tmax should certainly be no higher than this? I assume you are not seeing this?

                      I have a friend with an Intergas ECO RF 24 and a 10 zone evohome Wi-Fi and we are getting set points generated depending on the aggregate demand of the 10 zones (confirmed by an OpenTherm monitor and the boilers diagnostic software).

                      Capture3.jpg

                      I was testing several zones at the time, hence the demand was dropping off sometimes suddenly but should give you an idea of what is there and what should happen.

                      I am more than willing to invite Automated Home members over to our facility in Mid Wales to see this is action and discuss face-to-face? Maybe TB can even meet us there so you can ask questions directly?

                      Thanks,

                      Richard

                      Comment

                      • bruce_miranda
                        Automated Home Legend
                        • Jul 2014
                        • 2307

                        #12
                        OT works great in a single zone environment, or multiple zones all following a similar schedule. The moment you add multiple zone, each following their own schedule the usefulness wears off. This is due to the fact that it only takes a single zone that is outside of the proportional band to kick the boiler into full. When you have various zones, this is more than likely to mean that the boiler is running at full too often, simply to satisfy single zones. Other zones, if they are close to the set-point before the boiler full kicks in, will then often over shoot as a result.

                        Comment

                        • blowlamp
                          Automated Home Sr Member
                          • Apr 2017
                          • 98

                          #13
                          Originally posted by bruce_miranda View Post
                          OT works great in a single zone environment, or multiple zones all following a similar schedule. The moment you add multiple zone, each following their own schedule the usefulness wears off. This is due to the fact that it only takes a single zone that is outside of the proportional band to kick the boiler into full. When you have various zones, this is more than likely to mean that the boiler is running at full too often, simply to satisfy single zones. Other zones, if they are close to the set-point before the boiler full kicks in, will then often over shoot as a result.

                          This seems to be true judging by the user feedback I've seen here. By choosing to use full boiler output as often as it does, Evohome appears to be breaking the fundamental OpenTherm rule of keeping flow temperature low and the boiler in condensing mode whenever possible.

                          Comment

                          • StephenC
                            Automated Home Guru
                            • Feb 2017
                            • 102

                            #14
                            Originally posted by bruce_miranda View Post
                            OT works great in a single zone environment, or multiple zones all following a similar schedule. The moment you add multiple zone, each following their own schedule the usefulness wears off. This is due to the fact that it only takes a single zone that is outside of the proportional band to kick the boiler into full. When you have various zones, this is more than likely to mean that the boiler is running at full too often, simply to satisfy single zones. Other zones, if they are close to the set-point before the boiler full kicks in, will then often over shoot as a result.
                            +1 I can vouch for this behaviour. It doesn't work well in practice. Hence a need to have some additional control over flow temps on EvoHome side.

                            Comment

                            • StephenC
                              Automated Home Guru
                              • Feb 2017
                              • 102

                              #15
                              Originally posted by The EVOHOME Shop View Post
                              Hi Stephen,

                              Can you clarify why a Tmax setpoint is required from the controls?

                              The Intergas boiler I have at our training centre has the ability to set this manually (I designed our system with a 70 degree flow temp, so have limited it to this), but I understand that your Viessmann doesn't?

                              Most heating systems have a 75 degree flow temperature design point and I would imagine that once evohome is over its initial 'learning' phase, Tmax should certainly be no higher than this? I assume you are not seeing this?

                              I have a friend with an Intergas ECO RF 24 and a 10 zone evohome Wi-Fi and we are getting set points generated depending on the aggregate demand of the 10 zones (confirmed by an OpenTherm monitor and the boilers diagnostic software).

                              [ATTACH=CONFIG]1046[/ATTACH]

                              I was testing several zones at the time, hence the demand was dropping off sometimes suddenly but should give you an idea of what is there and what should happen.

                              I am more than willing to invite Automated Home members over to our facility in Mid Wales to see this is action and discuss face-to-face? Maybe TB can even meet us there so you can ask questions directly?

                              Thanks,

                              Richard

                              Hi Richard,

                              It appears that Viessmann have setup their boilers so that when OT controlled, it hands all control over to the controller. Their own controller for example has the option to set a max CH flow temp. When I challenged them on this, they told me Honeywell were at fault for not providing the capability in the EvoHome controller. It looks like the Nest v3 (from reading) also has the ability to set a max CH flow temp.

                              The only thing that limits how hot the water gets when the CH comes on (@ 100% demand - so any zone under the set point by 1.5 degrees C - although I saw it at the set point too) is the boiler hard limiter to avoid the water boiling!! That is around 82 degrees C, but I have seen 89 degrees C a few times.

                              I've done everything I can to try and work with this, but it's so hot I got overshoots of 2-4 degrees in zones as the HR92 closed too late (latent heat in radiator).

                              As for learning, 100% demand is 100% demand. That translates on OT bridge to boiler max CH flow temp value. Nothing to learn there. I had this in for 5 weeks and had to go back to BDR91 as it is the HR92 that learn (not EvoHome controller according to HW), and they didn't get any better at controlling (i.e. demanding less). I was even sent a new replacement OT bridge, but behaviour was the same.

                              Hope that explains things from a Viessmann owners perspective. I can't talk about behaviour for other boilers as I only have the one. ;-)
                              Last edited by StephenC; 30 July 2017, 08:00 AM.

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