Evohome hot water only at 30° with open therm connection

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  • Malcolm
    Automated Home Lurker
    • Dec 2015
    • 4

    Evohome hot water only at 30° with open therm connection

    Hello everybody

    I have installed the Evohome control unit with 16 Wi-Fi radiator valves and wireless
    open Therm Brige connected to our Vokera Unical i36 open Therm combination boiler, which all works really well and the boiler modulates up-and-down according to heat demand as expected.

    The only issue that I have is that now the hot water is only supplied at 30°C and their seems to be no way to increase its temperature as the manual hot water controls on the boiler no longer function as the open Therm connection bypasses them.
    Is there any advice that you can give me to resolve this problem or is there a way to control the hot water by the Evohome control with a combination boiler.

    Thanks

    Malcolm
  • emmeesse68
    Automated Home Guru
    • Dec 2014
    • 103

    #2
    I have more or less the same setup, with a Ferroli BlueHelix Pro 32C connected by OpenTherm and I'm not experiencing such issue.

    I built an OpenTherm gateway (http://otgw.tclcode.com/) and, as far as I can see, my R8810 never sends commands to set the DHW setpoint - it just reads the value sent by my boiler. So maybe there's something to set up at the boiler to default the DHW setpoint to whatever you like... I'd check with your boiler technical documentation or directly with their support.

    As far as I know, there's no way to control the DHW setpoint of a combi boiler because your EvoHome won't even be aware of it... It would drive a DHW cylinder kit but it's not designed to interfere with the DHW of a combi boiler.

    Could you temporarily disconnect your R8810 and test how your boiler works with DHW when no OpenTherm units are attached? I'd try and see what's the DHW setpoint and if it is possible to change it and if it is kept reattaching the R8810...

    Comment

    • Malcolm
      Automated Home Lurker
      • Dec 2015
      • 4

      #3
      Originally posted by Malcolm View Post
      Hello everybody

      I have installed the Evohome control unit with 16 Wi-Fi radiator valves and wireless
      open Therm Brige connected to our Vokera Unical i36 open Therm combination boiler, which all works really well and the boiler modulates up-and-down according to heat demand as expected.

      The only issue that I have is that now the hot water is only supplied at 30°C and their seems to be no way to increase its temperature as the manual hot water controls on the boiler no longer function as the open Therm connection bypasses them.
      Is there any advice that you can give me to resolve this problem or is there a way to control the hot water by the Evohome control with a combination boiler.

      Thanks

      Malcolm
      Thank you for your reply.

      My original installation used the BDR91 wireless relay box to activate the boiler from the Evohome controller, this just acted as a on off switch for the boiler when the rooms had reached their desired temperature and had no effect at all on the DHW.

      The temperature of the DHW was set by the hot water temperature selector on the boiler and we could achieve a temperature of 60° with no problem at all.
      The boiler was set by the heating temperature selector and had no opentherm control over it.

      On connecting the opentherm relay all the temperature selectors on the boiler were overridden and had no effect on the temperature of the boiler no matter what they were set too.

      I have disconnected the opentherm relay and set the water temperature to 60° and then reconnected the opentherm relay and it defaults back to 30° and there is no additional control on the main board to alter the DHW temperature so everything seems to be controlled by the open therm software.

      Vokera can supply a OpenTherm Wireless Programmable Room Thermostat 611 which also has the ability to alter DHW temperature on their combination boiler but unfortunately the Evohome controller does not have this ability, I can only assume that the boiler is not receiving any additional information for the DHW from the Evohome controller and is defaulting back to 30°.

      I will contact Vokera technical department and see if they can give any advice.

      Thanks again for your reply if there’s any more information from Vokera and let you know.

      Comment

      • Malcolm
        Automated Home Lurker
        • Dec 2015
        • 4

        #4
        I got a reply from Vokera technical Department and what they say is, unfortunately it is a compatibility issue with the Honeywell opentherm control and the boiler firmware and they have no answer to resolve it.
        So I guess the only solution would be either a boiler or Honeywell controller firmware update which I think either is very unlikely.
        If anyone else has any suggestions it would be much appreciated.

        Comment

        • paulockenden
          Automated Home Legend
          • Apr 2015
          • 1719

          #5
          So much for open standards...

          Comment

          • top brake
            Automated Home Legend
            • Feb 2015
            • 837

            #6
            I have escalated this case
            I work for Resideo, posts are personal and my own views.

            Comment

            • emmeesse68
              Automated Home Guru
              • Dec 2014
              • 103

              #7
              Originally posted by Malcolm View Post
              I got a reply from Vokera technical Department and what they say is, unfortunately it is a compatibility issue with the Honeywell opentherm control and the boiler firmware and they have no answer to resolve it.
              So I guess the only solution would be either a boiler or Honeywell controller firmware update which I think either is very unlikely.
              If anyone else has any suggestions it would be much appreciated.
              Not certain it would solve your issue, but I have mentioned an OpenTherm Gateway that you can put on the wire between your R8810 and your boiler. I use it mostly to monitor what's going on between boiler and EvoHome, but I think it is possible to use it to override commands exchanged between the two parties.

              If you like playing around with electronics it could be fun to build and useful to get insight. You can connect it to a computer via RS232 or USB (or WiFi... there are different versions on sale, even pre-built if you don't feel like soldering). Might not be as effective as a fix from Honeywell or Vokera (whoever's missing some OpenTherm spec), but it's probably quicker...

              Comment

              • Malcolm
                Automated Home Lurker
                • Dec 2015
                • 4

                #8
                Thank you for all your replies.

                I’ve got some more feedback from Vokera.

                Their service department can solve this issue by one of their engineers setting the hot water temperature with one of their 711 controllers .
                Then reconnect the evohome openfirm bridge and then all should be well.

                I guess the other option would be to build the R8810 opentherm control unit and set the hot water temperature with this unit and then reconnect the evhome openfirm bridge and hopefully it would retain the setpoint.

                Comment

                • sharpener
                  Automated Home Sr Member
                  • Jan 2015
                  • 78

                  #9
                  There seems to be a lack of joined-up thinking at Vokera. I had a similar problem with our Mynute HE 12kW - as soon as I added the weather compensation it over-rode the temp setting even when there was a demand for hot water.

                  Vokera technical were, in away, helpful. Having agreed it would have been a trivial software change to give the h.w. demand priority they could only suggest adding an external relay to do this by open circuiting the w/c sensor connection. This http://www.maplin.co.uk/p/5a-240vac-...re-relay-n13aw is small enough to go in the wiring center and works fine in practice. It also makes for a fast warm-up in the morning as the h.w. boosts the circulating temperature to 60C while the tank is heating, though in an ideal world the temp setting would be the higher of the w/c and h.w. demands on the few days in the year this would make a difference.

                  Maybe if you can derive an h.w. demand signal from somewhere you can implement something similar?

                  Comment

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