Evohome Help Please.

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  • Chrisnoy
    Automated Home Jr Member
    • Nov 2017
    • 12

    Evohome Help Please.

    Upgraded installation of Evohome with UFH- HCC80R + extension, DT92 thermostats per zone, HW using tank and CH upstairs, all radiators with HR92's. The original installation was an "S" plan system. The pipe to the UFH has been joined to the "T" point after the original CH motorised valve. There are two BD91's one in HW circuit controlling the original motorised valve for that and one controlling the other CH original motorised valve. The UFH pipe then travels through house until it gets to another new motorised valve followed by the controller and pump for the UFH zones.
    How should this be wired and bound? Is the plumbing correct? Do I need the CH motorised valve at all? Should I have a BD91 for the boiler?

    The boiler is an Oil fired unit non combi.

    Thanks for any help you can give me.
  • Dan_Robinson
    Automated Home Ninja
    • Jun 2012
    • 347

    #2
    That's a disaster of an installation.

    Get rid of the heating zone valve and bind the bdr to be heat demand.

    It's all in the manual.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

    Comment

    • bruce_miranda
      Automated Home Legend
      • Jul 2014
      • 2309

      #3
      also I don't understand why the UFH circuit is after the CH Valve. You then effectively can't run your underfloor without your upstairs being on. Like Dan said, since your entire CH is now under the control of Evohome get rid of all the CH zone valves both rad and UFH. One BDR91 should fire the boiler the other should operate the HW valve. That's it.

      Comment

      • Chrisnoy
        Automated Home Jr Member
        • Nov 2017
        • 12

        #4
        Originally posted by bruce_miranda View Post
        also I don't understand why the UFH circuit is after the CH Valve. You then effectively can't run your underfloor without your upstairs being on. Like Dan said, since your entire CH is now under the control of Evohome get rid of all the CH zone valves both rad and UFH. One BDR91 should fire the boiler the other should operate the HW valve. That's it.
        I hear what you say and I am obviously an amateur here, but without CH valves won't the pipes all get hot when the HW comes on? I realise there's no flow but having no CH valves sort of needs thinking outside of the box for an oldie like me.

        Comment

        • bruce_miranda
          Automated Home Legend
          • Jul 2014
          • 2309

          #5
          no where to go = no flow.

          So if Evohome has all the CH devices off the water isn't going to flow anywhere in the CH circuit. So no, even the pipes won't get hot beyond about a centimetre or two past the first T.

          Comment

          • mylesm
            Automated Home Guru
            • Nov 2015
            • 153

            #6
            Originally posted by Chrisnoy View Post
            I hear what you say and I am obviously an amateur here, but without CH valves won't the pipes all get hot when the HW comes on? I realise there's no flow but having no CH valves sort of needs thinking outside of the box for an oldie like me.
            When You take away the Existing CH Valves and replace with HR92s you dont have no Central heating valves as you say you actually have one CH valve for every rad so they will be closed if no CH Demand

            So HW can heat without heating Rads

            Comment

            • Chrisnoy
              Automated Home Jr Member
              • Nov 2017
              • 12

              #7
              Originally posted by mylesm View Post
              When You take away the Existing CH Valves and replace with HR92s you dont have no Central heating valves as you say you actually have one CH valve for every rad so they will be closed if no CH Demand

              So HW can heat without heating Rads
              Yep, I see it now, thanks to all for this advice, very much appreciated.

              Comment

              • Dan_Robinson
                Automated Home Ninja
                • Jun 2012
                • 347

                #8
                Good luck dude.
                Kind Regards - Dan Robinson (Jennings Heating Ltd)

                Comment

                • DorrisMancer
                  Automated Home Guru
                  • Nov 2017
                  • 129

                  #9
                  Maybe I've misunderstood the answers, but what's so wrong with a zone valve on the C/H? I have 3 zone valves: one for DHW and one for C/H (both controlled by BDR91s) and one for towel rads (currently controlled by a 7 day timer, see my earlier question about how to bring this under evohome timer control)

                  Comment

                  • Dan_Robinson
                    Automated Home Ninja
                    • Jun 2012
                    • 347

                    #10
                    The hr92 unit is effectively a zone valve in its own right.
                    Kind Regards - Dan Robinson (Jennings Heating Ltd)

                    Comment

                    • DorrisMancer
                      Automated Home Guru
                      • Nov 2017
                      • 129

                      #11
                      Yes, but I don't see any reason not to have a central C/H zone valve and it could be useful if one of the HR92s misbehaves, gets removed, or replaced with a TRV. Also, the zone valve is needed if you move house and want to revert to a timer+stat and take the expensive evohome system with you. I'm not trying to be argumentative, but I don't see why the OP should remove their zone valve - what have I not understood?

                      Comment

                      • mylesm
                        Automated Home Guru
                        • Nov 2015
                        • 153

                        #12
                        Originally posted by DorrisMancer View Post
                        Yes, but I don't see any reason not to have a central C/H zone valve and it could be useful if one of the HR92s misbehaves, gets removed, or replaced with a TRV. Also, the zone valve is needed if you move house and want to revert to a timer+stat and take the expensive evohome system with you. I'm not trying to be argumentative, but I don't see why the OP should remove their zone valve - what have I not understood?

                        Even without a CH Zone Valve if a HR92 misbehaves you can remove it and that Rad will heat whenever there is a heat demand which would be the same result as having a CH Zone Valve and removing HR92

                        In the ops position the Easy option is to disconnect CH Valve Electrically and Lock open it is then simply a matter of reconnecting to revert to original but be aware Valve can seize due to lack of movement

                        Comment

                        • DorrisMancer
                          Automated Home Guru
                          • Nov 2017
                          • 129

                          #13
                          It isn't the same result ... with a CH zone valve rads without an HR92 will not heat up when there's just a DHW heat demand.
                          I can't see any downside to having a zone valve and it's potentially beneficial to have one, that's why I was surprised at the recommendation in the responses to the OP and wondered whether I'd misunderstood some aspect of the system.
                          Last edited by DorrisMancer; 12 November 2017, 11:58 AM.

                          Comment

                          • bruce_miranda
                            Automated Home Legend
                            • Jul 2014
                            • 2309

                            #14
                            I don't think there is any harm in keeping the CH Valve, it just isn't required. If you keep it in then you are just introducing yet another dependency in the chain. Anyway, I don't like the mechanical locking of CH Valve suggestions. It doesn't open the port completely and could cause the Valve to seize. Best to wire it up to the boiler relay or pump.

                            Comment

                            • mylesm
                              Automated Home Guru
                              • Nov 2015
                              • 153

                              #15
                              Originally posted by DorrisMancer View Post
                              It isn't the same result ... with a CH zone valve rads without an HR92 will not heat up when there's just a DHW heat demand.
                              I can't see any downside to having a zone valve and it's potentially beneficial to have one, that's why I was surprised at the recommendation in the responses to the OP and wondered whether I'd misunderstood some aspect of the system.
                              And Conversly If a CH Zone Vlv Fails then no Rad heats its really up to the op no harm in having a Zone Valve just adds another possible point of Failure

                              I had Zone Valves I just removed Heads and opened Valves this way they are fully open all the time and HR92s do the individual Rad control but Could be reversed if needed

                              Comment

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