Atag IS24 Plus Evohome Plus Opentherm

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  • fergie
    Automated Home Sr Member
    • Mar 2017
    • 92

    #91
    I don’t have an outdoor sensor, but would be interested to hear if it will work with OT!

    Comment

    • RussC
      Automated Home Lurker
      • Dec 2017
      • 4

      #92
      Thanks for the info. Could you tell me more about the part you mentioned please? I assumes there would be screw terminal blocks on the boiler side, but it sounds like this this is not the case?

      Thanks

      Comment

      • HenGus
        Automated Home Legend
        • May 2014
        • 1001

        #93
        Originally posted by RussC View Post
        Thanks for the info. Could you tell me more about the part you mentioned please? I assumes there would be screw terminal blocks on the boiler side, but it sounds like this this is not the case?

        Thanks
        It is just a small adapter. My installer told me that he had boxes of them in his van!

        Comment

        • HenGus
          Automated Home Legend
          • May 2014
          • 1001

          #94
          Originally posted by fergie View Post
          I don’t have an outdoor sensor, but would be interested to hear if it will work with OT!
          What would it do that OT doesn’t? Evohome/OT’s fuzzy logic already calculates the TSet flow temperature depending on zone temperature differentials and demand. Unlike some other boilers, Atag/OT also over-rides the manual CH max flow control.

          Comment

          • fergie
            Automated Home Sr Member
            • Mar 2017
            • 92

            #95
            In a perfect world the sensor would tell the boiler to work harder or work less depending on the temp outside. But that then may start working against evohome. Even better would be if evohome could use the local weather to adjust its demands.

            Comment

            • HenGus
              Automated Home Legend
              • May 2014
              • 1001

              #96
              Originally posted by fergie View Post
              In a perfect world the sensor would tell the boiler to work harder or work less depending on the temp outside. But that then may start working against evohome. Even better would be if evohome could use the local weather to adjust its demands.
              My local weather (and the App is still not showing it), is 12 miles away and a 1000ft lower. In Winter, morning temperatures are usually 3 to 6C lower than we get because of the effects of lapse rates and katabatic drainage (cold air flowing down slopes). Others have commented that weather compensation works best in Spring and Autumn: not Winter.

              Comment

              • RussC
                Automated Home Lurker
                • Dec 2017
                • 4

                #97
                Originally posted by HenGus View Post
                It is just a small adapter. My installer told me that he had boxes of them in his van!
                Should be straightforward then, thanks.

                Comment

                • RussC
                  Automated Home Lurker
                  • Dec 2017
                  • 4

                  #98
                  Thought I'd give it a few days before reporting back. New economiser 27 went in on Thursday, and so far so good. Just works perfectly with evohome, after a day or two characterising they're working together brilliantly, every zone accurately regulated and minimal overshoot. Tonight it's dropped to -11C outside and it's just transparent to the user, no adjusting temperature set points... Brilliant!

                  Comment

                  • Hankscorpion
                    Automated Home Lurker
                    • Aug 2017
                    • 8

                    #99
                    I have just had an Atag IC 35 installed. I spoke with their technical team about wiring OT thermostat and they said I could use the black adapter that comes in the unit as it will fit on the blue connection point in the boiler. I had to knock off a small plastic tag but this works and my OT thermostat is up and running and commincating with the Evohome controller. Thought this might be useful for people who might be trying to order the blue adaptor.

                    Comment

                    • rotor
                      Automated Home Guru
                      • Aug 2015
                      • 124

                      Sorry for reviving an ancient thread! @HenGus, almost three years down the track, are you happy you went with OpenTherm on the ATAG? I'm about to get an iS 24 installed, and having the option to get OpenTherm but wondering if it's worth the added complexity (needing the OpenTherm bridge, the different valve and the labour will probably add £300-400 to the bill). Thanks!

                      Comment

                      • bruce_miranda
                        Automated Home Legend
                        • Jul 2014
                        • 2307

                        A different valve just because of OT? That's interesting.

                        Comment

                        • rotor
                          Automated Home Guru
                          • Aug 2015
                          • 124

                          Originally posted by bruce_miranda View Post
                          A different valve just because of OT? That's interesting.
                          The open by default, motor to close valve.

                          Comment

                          • bruce_miranda
                            Automated Home Legend
                            • Jul 2014
                            • 2307

                            Do what I did. Put in a normally closed valve and make it open with the Pump. That way you can have any configuration you want. This method even deals with Pump overrun, Frost protection etc

                            Comment

                            • HenGus
                              Automated Home Legend
                              • May 2014
                              • 1001

                              Originally posted by rotor View Post
                              Sorry for reviving an ancient thread! @HenGus, almost three years down the track, are you happy you went with OpenTherm on the ATAG? I'm about to get an iS 24 installed, and having the option to get OpenTherm but wondering if it's worth the added complexity (needing the OpenTherm bridge, the different valve and the labour will probably add £300-400 to the bill). Thanks!
                              I have moved home in the past 18 months so my experience of OT/Atag is based on 14 months of use. Unlike some boilers, the Atag worked as it should under OT control; ie, hot water re-heating is controlled to the Max TSet temperature set within the boiler controls. The valve question is an interesting one. The manual states that there is a requirement for what Atag calls a modified diverter valve. I am guessing that this needed whether or not you go for OT control. OT itself is nothing more than the cost of the bridge and a length of low voltage wire! My installer converted my existing 'S' plan by replacing the CH zone valve with an inline valve (power off/OPEN) which he wired in series with the HW zone valve such that when the HW valve opened the CH valve closed. I re-configured the controller.

                              Would I bother to install OT again? Yes, I probably would. In truth, the only bits of Evohome that gave me any issues after OT was installed was the CS92A and the occasional loss of comms from a HR92. Building from scratch, I would probably not install the hot water control.

                              I haven't bothered with Evohome in my new home as I would not like to leave my wife with a system that she doesn't understand with little help available from installers and family.

                              Comment

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