Evohome BDR 91 time on/off

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  • Mickjohn
    Automated Home Sr Member
    • Mar 2015
    • 68

    Evohome BDR 91 time on/off

    Hi

    I have an Evohome set up( wifi controller) BDR91 with 7 radiators ( no hot water) all working fine ( except when Honeywell servers go down) I am logging temps with Domoticz via web API ( I have no programming experience) and all look good.

    Under switches tab in Domoticz I see EvoTouch, which I assume is the base controller but cant seem to do anything with it.

    Is there any way to log when boiler switches on and off?

    Many thanks

    Mick
  • bruce_miranda
    Automated Home Legend
    • Jul 2014
    • 2307

    #2
    If you were using an HGI80 or similar then under the Switches Tab you would see at least 2 relays called CH Valve and Boiler. These track the Heat Demand that is being sent to the BDR91. This isn't visible via the Web API. Heat Demand is different to the actual switching of the boiler, which is actually performed using TPI. As it turns out, I have just submitted a PR to the Domoticz project to create additional Zone Relay devices that actually attempt to track the Switching On/Off of the BDR91 i.e. stay in step to the LED Green light.
    Another thing to note is boiler being switched on is different from Flame being On. So generally Heat Demand > BDR91 TPI > Flame On. Sadly, all of this can only be tracked via sniffing the radio signals and not accessible via the web API.

    Comment

    • rs1987
      Automated Home Jr Member
      • Nov 2019
      • 44

      #3
      Originally posted by bruce_miranda View Post
      Sadly, all of this can only be tracked via sniffing the radio signals and not accessible via the web API.
      It would be really nice if Honeywell were to expose the web API and make it more functional so that 3rd party tools like Domoticz could add value. This would greatly improve the product by surrounding it with an ecosystem of capable software. One wonders why they've not done so already.

      Comment

      • bruce_miranda
        Automated Home Legend
        • Jul 2014
        • 2307

        #4
        To be fair to Honeywell, their HGI80 is meant to be the way approved 3rd parties integrate with Evohome. The Web API is actually not approved but they can't stop it.

        Comment

        • Mickjohn
          Automated Home Sr Member
          • Mar 2015
          • 68

          #5
          Bruce_miranda

          Many thanks for your explanation its much appreciated. I have looked for an HG180 but they seem to be a bit thin on the ground do you know of anything similar?

          Thanks again

          Mick

          Comment

          • bruce_miranda
            Automated Home Legend
            • Jul 2014
            • 2307

            #6
            At the moment, if I had to recommend another RF capture device it would have to be the NanoCUL or an RFBee. You will have to load some custom firmware on it, which a few of us are developing. If you don't have OpenTherm then the firmware is pretty stable. The OT Bridge is the only device that is causing some issues.

            P.S. I am looking to get rid of a few of my RFBees + UARTBees. PM me if you are interested. I'll load up the firmware on it before I send it out, so you will be up and running straight away.

            Comment

            • smar
              Automated Home Sr Member
              • Feb 2018
              • 57

              #7
              Originally posted by bruce_miranda View Post
              If you don't have OpenTherm then the firmware is pretty stable. The OT Bridge is the only device that is causing some issues.
              I've been thinking about adding OpenTherm to my setup. What problems are you encountering with the OT bridge? Is there somewhere where you are discussing this?

              Thanks.

              Comment

              • bruce_miranda
                Automated Home Legend
                • Jul 2014
                • 2307

                #8
                there is no problem with the OT Bridge itself. It's just that the DIY radio interfaces have the most problems with messages sent out by the OT Bridge. Having said that the success rate is quite high, so nothing to worry about

                Comment

                • smar
                  Automated Home Sr Member
                  • Feb 2018
                  • 57

                  #9
                  Originally posted by bruce_miranda View Post
                  there is no problem with the OT Bridge itself. It's just that the DIY radio interfaces have the most problems with messages sent out by the OT Bridge. Having said that the success rate is quite high, so nothing to worry about
                  Great, thanks. As you've had your OT bridge in place for a few years now, is it something you would recommend based on your experience (I have a Vaillant condensing system boiler, and my DHW is also controlled by evohome)?

                  Comment

                  • bruce_miranda
                    Automated Home Legend
                    • Jul 2014
                    • 2307

                    #10
                    I have only ever had OT on my Vaillant. I never used Evohome with a BDR91 boiler demand. So I have nothing to compare against. But the fact that I see low Target Flow temperatures when all my zones are at their setpoint gives me hope that I am running a theoretically more efficient system.

                    Comment

                    • paulockenden
                      Automated Home Legend
                      • Apr 2015
                      • 1719

                      #11
                      The benefit of OT is that once your house is up to temperature and just needs to be kept warm you'll have a steady flow of warm water running around your heating circuit rather than short pulses of very hot water.

                      Comment

                      • smar
                        Automated Home Sr Member
                        • Feb 2018
                        • 57

                        #12
                        Thanks and sounds good.

                        Comment

                        • smar
                          Automated Home Sr Member
                          • Feb 2018
                          • 57

                          #13
                          Originally posted by paulockenden View Post
                          The benefit of OT is that once your house is up to temperature and just needs to be kept warm you'll have a steady flow of warm water running around your heating circuit rather than short pulses of very hot water.
                          Yes, that is what I had figured. Assuming that I don't have hot water priority, then I'm guessing that some of the benefits would be negated?

                          Comment

                          • DBMandrake
                            Automated Home Legend
                            • Sep 2014
                            • 2361

                            #14
                            Originally posted by smar View Post
                            Yes, that is what I had figured. Assuming that I don't have hot water priority, then I'm guessing that some of the benefits would be negated?
                            If your system has a heating zone valve you could wire in hot water priority fairly easily.

                            Do you have both heating and hot water zone valves and two BDR91's controlling them ? If so just take the feed for the relay contacts for the heating zone valve from the normally closed contact of the hot water zone valve - when the hot water zone valve goes on it will force the heating zone valve off no matter what the heating BDR91 does.

                            Comment

                            • smar
                              Automated Home Sr Member
                              • Feb 2018
                              • 57

                              #15
                              Originally posted by DBMandrake View Post
                              If your system has a heating zone valve you could wire in hot water priority fairly easily.

                              Do you have both heating and hot water zone valves and two BDR91's controlling them ? If so just take the feed for the relay contacts for the heating zone valve from the normally closed contact of the hot water zone valve - when the hot water zone valve goes on it will force the heating zone valve off no matter what the heating BDR91 does.
                              Yes, I do have the separate zone valves/BDR91s, though I had previously disconnected the one for raditators, and left it in the open position (it had started to stick - even though it was only about a year old - possibly due to the constant opening/closing). I'll look at getting this reinstated. Should be easy enough to rewire the way you've described.

                              I also have an UFH manifold which has its own water temperature control. Would you recommend taking this offline as well with hot water priority, or leave this as is, given that it has its own water temperature regulation?

                              Final question - I'm assuming that the half an hour/40 minutes or so that the hot water may take to heat up shouldn't impact the room temperatures much, given the hot water priority?

                              Comment

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