Boiler with separate HW and CH max and OpenTherm

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • bruce_miranda
    Automated Home Legend
    • Jul 2014
    • 2307

    Boiler with separate HW and CH max and OpenTherm

    I have a Vaillant boiler which could use two different Max Flow temperatures depending on whether it was Hot Water (HW) or Central Heating (CH) demand. Problem is that you can use this feature only with Vaillant's own eBus controllers. That is not a route I want to go down especially since I have Evohome and OpenTherm controlling the boiler.

    Currently the way OpenTherm works with my boiler is that there is only a single Heating demand and OpenTherm sets the maximum flow temperature required based on the demand it receives from Evohome. My boiler allows me to limit the flow temperature but only the Central Heating max temperature knob is operational, the Hot Water temperature knob continues to stay redundant.

    Are there any boilers what work with OpenTherm where the max flow temperatures can be set separately and they work as such? I'm trying to see if it is even possible to have a lower max flow temperature when there is only CH demand and a higher max flow temperature when there is HW demand - while still using Opentherm.

    Are there any Vaillant boiler users that used to use an eBus controller before and how have connected an OT Bridge via the VR33? What happens then?
  • Dan_Robinson
    Automated Home Ninja
    • Jun 2012
    • 347

    #2
    Intergas.

    Ideal Vogue

    I know which one I would have. And do have. Running in this configuration too.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

    Comment

    • bruce_miranda
      Automated Home Legend
      • Jul 2014
      • 2307

      #3
      So is your boiler able to use different max settings based on whether the demand is HW or CH and that demand is coming via the Evohome Opentherm bridge?

      Comment

      • Dan_Robinson
        Automated Home Ninja
        • Jun 2012
        • 347

        #4
        Hot water demand comes from the hot water bdr. Evohome does not give a specific hot water command. Just a demand for 100%.
        Kind Regards - Dan Robinson (Jennings Heating Ltd)

        Comment

        • bruce_miranda
          Automated Home Legend
          • Jul 2014
          • 2307

          #5
          So are you using Opentherm and a BDR together to drive the boiler?

          Comment

          • Dan_Robinson
            Automated Home Ninja
            • Jun 2012
            • 347

            #6
            Yep. OpenTherm is pretty pointless in hot water. Bdr activates the boiler for hot water. Boiler controls a diverter valve for the cylinder.

            Valve sits in Heating mode normally. OpenTherm bridge then regulates the heating setpoint.
            Kind Regards - Dan Robinson (Jennings Heating Ltd)

            Comment

            • bruce_miranda
              Automated Home Legend
              • Jul 2014
              • 2307

              #7
              OK excellent. So clearly your boiler has two switched inputs to allow this to happen. Which boiler is it BTW? I agree that OpenTherm is pretty pointless in HW, but my silly boiler can only switch between HW and CH mode via the eBUS as opposed to switched inputs. Hence I am having to think of another solution to achieve what you have managed.

              Comment

              • Dan_Robinson
                Automated Home Ninja
                • Jun 2012
                • 347

                #8
                You are discovering why the more discerning of us call them Faillant leakoTec.

                I have the Intergas Eco RF 24 installed as a system boiler on the D Plan.

                This is my go to boiler and configuration for any project with efficiency and performance on the spec sheet.

                On the 17th I start a job which has been named the "36DD Plan" as it is a brace of Intergas Eco RF 36 boilers with a 400 litre twin c coil cylinder. Each boiler has a coil on hot water priority.

                Because of the size of the house and Honeywell not letting mere mortals play with their posh toys, I have to use heatmiser controls and that will be linked with Control 4 etc. I will compensate the heating using the inTouch app (part of the boilers) which will give a very effective alternative.

                Here is a single boiler version doing 240 square metres of ufh across 4 floors and couple of radiators and towel rails:

                20160729_121434.jpg


                I was "summoned" to an M&E meeting at short notice, so knocked this up the night before to show them how it worked :

                Schematics.jpg
                Kind Regards - Dan Robinson (Jennings Heating Ltd)

                Comment

                • bruce_miranda
                  Automated Home Legend
                  • Jul 2014
                  • 2307

                  #9
                  So are there any boilers that have the ability to have different HW and CH flow temperatures and where the OperTherm Gateway is able to tell the boiler what it is trying to heat? either HW or CH, or is the Opentherm gateway always assuming that all boilers are Heat Only and makes no difference between HW and CH, so just run everything at a higher flow temperature to satisfy both?

                  Comment

                  • top brake
                    Automated Home Legend
                    • Feb 2015
                    • 837

                    #10
                    Originally posted by bruce_miranda View Post
                    So are there any boilers that have the ability to have different HW and CH flow temperatures and where the OperTherm Gateway is able to tell the boiler what it is trying to heat? either HW or CH, or is the Opentherm gateway always assuming that all boilers are Heat Only and makes no difference between HW and CH, so just run everything at a higher flow temperature to satisfy both?
                    the boiler will modulate to the flow temperature that the controller requests

                    by Vaillant ecoTECplus with VR33 adapter and evohome with OT bridge does exactly this

                    normal flow temp circa 45degC, when there is hot water cylinder demand the flow temperature is increased to the max set at the boiler, in my case 70degC

                    the boiler simply responds to the new flow temp setpoint

                    make sense?
                    I work for Resideo, posts are personal and my own views.

                    Comment

                    • bruce_miranda
                      Automated Home Legend
                      • Jul 2014
                      • 2307

                      #11
                      I understand how the OT bridge works. But it isn't using the capabilities of many boilers that can have a different flow temperature set for HW and CH. So your boiler is always running towards the higher of those two. If Vaillants own controls, if the OT bridge was able to tell the boiler what it was heating then you could set the max flow for CH to be atleast 5 or 10 degrees lower than HW.

                      Comment

                      • top brake
                        Automated Home Legend
                        • Feb 2015
                        • 837

                        #12
                        Originally posted by bruce_miranda View Post
                        I understand how the OT bridge works. But it isn't using the capabilities of many boilers that can have a different flow temperature set for HW and CH. So your boiler is always running towards the higher of those two. If Vaillants own controls, if the OT bridge was able to tell the boiler what it was heating then you could set the max flow for CH to be atleast 5 or 10 degrees lower than HW.
                        but the OT controller achieves this as the master - the boiler just does as commanded; high temp for DHW, lower temp for CH
                        I work for Resideo, posts are personal and my own views.

                        Comment

                        • Dan_Robinson
                          Automated Home Ninja
                          • Jun 2012
                          • 347

                          #13
                          Is Bruce conflating Dual flow temperature with flow share/hot water priority?

                          There is however the issue with burner control logic, and the boiler ramping up for heating slowly and going straight to full kw for hot water. The bridge does not have influence over this.
                          Kind Regards - Dan Robinson (Jennings Heating Ltd)

                          Comment

                          • bruce_miranda
                            Automated Home Legend
                            • Jul 2014
                            • 2307

                            #14
                            Originally posted by top brake View Post
                            but the OT controller achieves this as the master - the boiler just does as commanded; high temp for DHW, lower temp for CH
                            It doesn't. If a zone is outside of the proportionate band it will ramp the boiler up to the same max as when it needs to heat hot water..

                            Comment

                            • top brake
                              Automated Home Legend
                              • Feb 2015
                              • 837

                              #15
                              Originally posted by Dan_Robinson View Post
                              Is Bruce conflating Dual flow temperature with flow share/hot water priority?

                              There is however the issue with burner control logic, and the boiler ramping up for heating slowly and going straight to full kw for hot water. The bridge does not have influence over this.
                              yes boiler and burner control logic has an effect too, the OT master can ask but if the boiler is reluctant...

                              how quickly/dramatically the boiler responds can be tuned on some boilers
                              I work for Resideo, posts are personal and my own views.

                              Comment

                              Working...
                              X