Dual heat demand relays on evohome?

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  • sandyman
    Automated Home Sr Member
    • Mar 2016
    • 85

    Dual heat demand relays on evohome?

    Has anyone figured out a way to have evohome activate heat demand relay "1" for group 1 of zones, and heat demand relay "2" for group 2 of zones?

    I'm looking at heat pump design for my house with LLH separating primary and secondary side, separately pumped secondary-side F+R circuits for upstairs and downstairs. Heat pump's controller takes care of pump speeds and temperatures. But we need a way to have evohome tell the heat pump's controller "upstairs needs heat" vs "downstairs needs heat" so it turns on the right secondary pump.

    I could buy a second evo controller and re-bind the upstairs HR92's to that controller. effectively two independent systems, each individually and independently talking to the HP controller.
    replicating my pre-evo setup when we had separate upstairs and downstairs zones (S plan plus) and two room stats on the hall and landing. Not a nice workaround though.

    obviously the evohome controller has the capability to control more than one demand relay, but its design to have those as different functions DHW and CH. Setting those up as CH1 and CH2 doesn't seem to be a thing in the installer settings or the manuals?

    does the HCE80 UFH controller have this capability? it looks to me like it could in theory based on the hardware, but is probably not capable of being configured that way?

    or would I be better to have Home Assistant as the brain - it knows via its evohome integration the zone temps and whether they are calling for heat or not, so with a suitable automation written within HA to monitor that, aggregate them up into two bundles, each bundle switching a relay on an output board from my HA box, I could probably home-brew it?

    ta
    Ian
  • kevinsmart
    Automated Home Ninja
    • Sep 2018
    • 257

    #2
    I think you will need another Evo controller.

    Comment

    • sandyman
      Automated Home Sr Member
      • Mar 2016
      • 85

      #3
      Originally posted by kevinsmart View Post
      I think you will need another Evo controller.

      https://honeywellhomeacs.force.com/l...language=en_US
      thanks. sorry for delay replying. that was conclusion I came to as well. Investing more in evohome controllers and running two control systems on same circuit is not where I want to go. I'm looking at alternatives now (see thread I just asked).

      Comment

      • bruce_miranda
        Automated Home Legend
        • Jul 2014
        • 2307

        #4
        Another option which is super messy is to use two UFH manifold controllers. They effectively become your zone relays but then you will need to have wired TRV controllers in each zone

        Comment

        • sandyman
          Automated Home Sr Member
          • Mar 2016
          • 85

          #5
          Originally posted by bruce_miranda View Post
          Another option which is super messy is to use two UFH manifold controllers. They effectively become your zone relays but then you will need to have wired TRV controllers in each zone
          I have no UFH. only rads with HR92's.

          Comment

          • bruce_miranda
            Automated Home Legend
            • Jul 2014
            • 2307

            #6
            I think you misunderstood, you are not using the UFH controller to control the UFH, but to group the TRVs with wired controllers. Like I said, it's messy.

            What I don't quite understand yet is the use case to have groups of TRVs to be set? Perhaps if you explained what you are trying to do, we can suggest another less messy option

            Comment

            • sandyman
              Automated Home Sr Member
              • Mar 2016
              • 85

              #7
              the use case is for a heat pump (RED UHE) that has a integrated manifold / Low loss header that it dynamically controls . Both the 1ary and 2ary pumps are variable speed PWM controlled by the HP. secondary side it has capacity for multiple zones, one piped flow+return for each pipework zone, each with its own pump , PWM controlled by the heatpump. return temps sensors independently in each pipework zone , heat pump uses these to figure out how much heat needed overall, it does the maths, that bit not my problem its an integrated system.

              what I want is to still have the per-room control and all the other benefits of evohome AND be able to have evohome tell the heat pump controller by means of the on/off state of relays:
              - upstairs is calling for heat yes/no
              - downstairs is calling for heat yes/no

              this is slightly simplified for the purposes of discussion because I actually have two downstairs F+R loops to different legs of the house. One is quite convoluted pipe path (long story) and has incidentally been proven to benefit from a higher flow rate on the pump. So I am fairly sure that by separating my secondary side into its component parts, I'll get better comfort and the heat pump will be able to work at its most efficient.

              pseudocode

              if <bed1 or bed2 or bed3 or bed4 or bath1 or landing are calling for heat> set "upstairs calling for heat relay" to ON
              if <hall or kitchen or TVSnug are calling for heat> set "downstairs1 calling for heat relay" to ON
              if <Lounge or diningroom or conservatory are calling for heat> set "downstairs2 calling for heat relay" to ON

              then the heat pump controller will do the rest....
              in the situation where only 1 room in a zone is on just a little bit, then the heat pump controller will figure this out by means of return temps and/or pump sensors, and modulate the pump speed and heat into that zone down. If all rooms in that zone fully open, HP will go flat out...


              all I can do with evohome (unless there is some cunning plan!) is
              if <any room calling for heat> set "call for heat relay" to ON
              so I can't separate up, down1 and down2. A working solution, but not what I want.
              that is the fundamental limitation of evohome that I am trying to overcome.

              its related to S-plan plus - with an upstairs zone valve and a downstairs zone valve, a thermostat upstairs activating that zone valve, and a thermostat downstairs activating the other zone valve, if either zone valve is active, then the heat source and (single) pump would be activated. This is EXACTLY what I had pre-evohome. If I still had this it would be a piece of ***s to do, we'd attach upstairs thermostat's output to the "zone1 call for heat" input on the heat pump controller, downstairs one's to the "zone2 call for heat" on the controller and we'd be done. Of course, I wouldn't have per-room control, which I don't want to give up........

              ta
              Ian

              Comment

              • bruce_miranda
                Automated Home Legend
                • Jul 2014
                • 2307

                #8
                You are probably going to have to use 2 Evohome controllers, one for each floor. But they both can use a single boiler relay in case that is what you needed too.

                Comment

                • bruce_miranda
                  Automated Home Legend
                  • Jul 2014
                  • 2307

                  #9
                  BTW, you don't have to use the Heat Pump manifold. Your heat pump has a single Flow and Return that is then being pushed into a multi zone manifold designed for houses that have no zoning. Since you already have a per zone heating controller I.e. Evohome, you could use the Heat Pump as a single heating loop boiler replacement and let Evohome manage the zones

                  Comment

                  • sandyman
                    Automated Home Sr Member
                    • Mar 2016
                    • 85

                    #10
                    Originally posted by bruce_miranda View Post
                    BTW, you don't have to use the Heat Pump manifold. Your heat pump has a single Flow and Return that is then being pushed into a multi zone manifold designed for houses that have no zoning. Since you already have a per zone heating controller I.e. Evohome, you could use the Heat Pump as a single heating loop boiler replacement and let Evohome manage the zones
                    yeah that is an option with some heat pump designs. straight heat source swap single loop. however, one half of my secondary pipework side will benefit from being able to have a boosted flow rate compared to the other half. especially given that flow rate will have to be higher for the heat pump vs boiler. but this one, the manifold is part of their system, it takes care of zone valve towards DHW as well.

                    Comment

                    • sandyman
                      Automated Home Sr Member
                      • Mar 2016
                      • 85

                      #11
                      Originally posted by bruce_miranda View Post
                      You are probably going to have to use 2 Evohome controllers, one for each floor. But they both can use a single boiler relay in case that is what you needed too.
                      one way I had thought about doing this was to relegate evohome's own controller to purely being controller for the TRV's. No longer any BDR91 anywhere in the system to call for heat (unless evohome insists on having one, in which case I still have one, but connect it to nothing).

                      then given that via the evohome API we can discover which zones are calling for heat, build some electronics and write some code to activate some microcontroller relays. relay 1 or 2 or 3 depending on which zones want heat. relays 1 2 3 connect to heat pumps inputs, heatpump controller does the rest. given that I already use homeassistant and have a number of ESP8266 and ESP32 's doing temp monitoring, I'd do it with another one of those. I already have the evohome integration running in homeassistant so I can pretty well see how I'd do it.
                      however, this would put a reliance on the cloud API (i.e. working internet) to be able to have heat, which I am not keen on.

                      I have heard that there may be solutions for consuming the raw RF data over the air directly into a microcontroller, at which point arbitrary logic can be done, is this feasible?

                      Comment

                      • lloyd
                        Automated Home Guru
                        • Oct 2020
                        • 160

                        #12
                        Originally posted by sandyman View Post

                        I have heard that there may be solutions for consuming the raw RF data over the air directly into a microcontroller, at which point arbitrary logic can be done, is this feasible?
                        Certainly feasible. You can eavesdrop on the RF and use this in HA. Much more powerful than the evohome cloud integration. That is what I do. Take a look at https://github.com/zxdavb/ramses_cc

                        I'm sure you can achieve what you want with evohome, HA and a few extra bits.

                        Comment

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