Evohome: TPI with multiple controllers

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  • tobybuk
    Automated Home Lurker
    • Dec 2017
    • 6

    Evohome: TPI with multiple controllers

    I have a system that needs more than 12 zones, so I have two Wifi Controllers and double bound the BDR91 than controls the heating side of the system.

    My question is how does this function with respect to TPI?

    Does the controller drive TPI and send on/off signals to the BDR91? Does the BDR91 remember each controller instruction and only turn off when both controllers are sending off? If this is the case I cannot see how a TPI system could operate. Wouldn't the controllers be fighting each other?

    Or does the BDR91 control TPI by receiving demand levels from each controller and combining them?

    Thanks

    Toby
  • Dan_Robinson
    Automated Home Ninja
    • Jun 2012
    • 347

    #2
    BDR aggregates the demand/loading from the base units and fires the boiler according to this
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

    Comment

    • filbert
      Automated Home Guru
      • Oct 2017
      • 162

      #3
      Pardon my ignorance, but what is 'TPI'???

      Comment

      • Chrisnoy
        Automated Home Jr Member
        • Nov 2017
        • 12

        #4
        I always find Google a great help!

        Comment

        • Dan_Robinson
          Automated Home Ninja
          • Jun 2012
          • 347

          #5
          Its a control strategy that makes the best use of an on/off signal to smooth temperatures in a heating system.
          Kind Regards - Dan Robinson (Jennings Heating Ltd)

          Comment

          • filbert
            Automated Home Guru
            • Oct 2017
            • 162

            #6
            Originally posted by Chrisnoy View Post
            I always find Google a great help!
            I did that but it didn't seem to make sense in this context.. I'm not sure I understand but it isn't relevant to my single controller system, so it's not important. Also, it sounds like it's more concerned with optimisation, which I don't use.
            Last edited by filbert; 15 January 2018, 11:21 PM. Reason: clarify

            Comment

            • Dan_Robinson
              Automated Home Ninja
              • Jun 2012
              • 347

              #7
              It's not directly related to optimisation.

              The BDR can coordinate 4 controllers and ensure a good firing strategy for the boiler.
              Kind Regards - Dan Robinson (Jennings Heating Ltd)

              Comment

              • Edinburgh2000
                Automated Home Guru
                • Dec 2016
                • 134

                #8
                Originally posted by filbert View Post
                Pardon my ignorance, but what is 'TPI'???
                I know Dan Robinson and others favour short posts on here but, in case you are like me and prefer the full monty explanation of how things work, you might find the discussion here enlightening:



                I certainly learned a lot from DBMandrake's helpful clear and full explanations.

                And TPI stands for "Time Proportional and Integral" and is a control methodology that combines proportional control (output varying with temperature) and integral control (output increasing/decreasing with the time that the temperature is below/above the setpoint).

                Comment

                • dty
                  Automated Home Ninja
                  • Aug 2016
                  • 489

                  #9
                  I'd like to know how this works in an OpenTherm scenario! Presumably, broadly the same - the OT bridge is bound to both controllers and aggregates the demand to come up with a flow temperature (instead of a duty cycle %).

                  Comment

                  • Dan_Robinson
                    Automated Home Ninja
                    • Jun 2012
                    • 347

                    #10
                    Pretty much mate.

                    Think of the bdr and the OpenTherm bridge as interpreters for the boiler.
                    Kind Regards - Dan Robinson (Jennings Heating Ltd)

                    Comment

                    • Dan_Robinson
                      Automated Home Ninja
                      • Jun 2012
                      • 347

                      #11
                      Originally posted by Edinburgh2000 View Post
                      I know Dan Robinson and others favour short posts on here but, in case you are like me and prefer the full monty explanation of how things work, you might find the discussion here enlightening:



                      I certainly learned a lot from DBMandrake's helpful clear and full explanations.

                      And TPI stands for "Time Proportional and Integral" and is a control methodology that combines proportional control (output varying with temperature) and integral control (output increasing/decreasing with the time that the temperature is below/above the setpoint).
                      Indeed, I like concise posts because I contribute (and benefit) from the forum whilst at work, which is not often sitting at a desk. I think K someone you office based members might be surprised if you knew from where my posts were coming from. .
                      Kind Regards - Dan Robinson (Jennings Heating Ltd)

                      Comment

                      • paulockenden
                        Automated Home Legend
                        • Apr 2015
                        • 1719

                        #12
                        Simon (dbmandrake) often posts very long replies, but don't make the mistake of dismissing them as TL;DR - they are always well considered and well explained. I've learned a lot from them.,

                        Comment

                        • The EVOHOME Shop
                          Site Sponsor
                          • Dec 2014
                          • 483

                          #13
                          Originally posted by paulockenden View Post
                          Simon (dbmandrake) often posts very long replies, but don't make the mistake of dismissing them as TL;DR - they are always well considered and well explained. I've learned a lot from them.,
                          Indeed, Simon is a great asset to this and other forums...

                          Comment

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