Underfloor heating with Evohome

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  • BuxtonJim
    Automated Home Jr Member
    • Aug 2018
    • 45

    #16
    Originally posted by bruce_miranda View Post
    The HCC80R is required only if you have a single manifold serving multiple rooms and you want zone control. If you have a pump/manifold per room or zone you just buy a T87RF and use the wall stat as your sensor and the BDR91 the Zone Valve actuator.
    This is exactly what I've done in a similar UFH situation and the system works a treat. There is no need for the rather expensive HCC80R with a single zone. This saved me a packet thanks to advice in this forum!

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    • 1animal1
      Automated Home Jr Member
      • Jan 2018
      • 39

      #17
      Can anyone confirm, when buying a manifold - if I need the blending valve? From what I can make out, it's for protection, ensuring the max heat going through is limited

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      • gordonb3
        Automated Home Ninja
        • Dec 2016
        • 273

        #18
        Originally posted by 1animal1 View Post
        Can anyone confirm, when buying a manifold - if I need the blending valve? From what I can make out, it's for protection, ensuring the max heat going through is limited
        Had to look that up. Amazed to see they still sell passive stuff like that. I had my UFH installed about 8 years ago and the manifold itself is actually doing the mixing. The system uses two wired thermostatic valves for controlling input and output flow and also regulates the motor, which saves me around 600kWh per year in electricity usage. The computer also features a protection mechanism for the pump by periodically cranking the motor to free it from any pollution/residue that might be in the water. Obviously, if I'd use a BDR91 to control my UFH that would defeat that protection mechanism and I still have adding a third valve to be controlled by an HR92 on my todo list.
        Last edited by gordonb3; 1 January 2019, 08:25 PM.

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        • 1animal1
          Automated Home Jr Member
          • Jan 2018
          • 39

          #19
          Thanks Gordon... I have looked high and low at manifolds and can only see either bare manifolds, or those with the pump and blend valve attached. Are you suggesting you have something different to what's generally available?

          The only other thing I'm questioning is the pump circ, apart from an energy saving, surely the protection mechanism is a bit of a fad if it's an in use system? A pressurised system with the correct inhibitor, new or flushed shouldn't have an issue that requires such a protection mechanism? Tell me how i am wrong in my thinking

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          • gordonb3
            Automated Home Ninja
            • Dec 2016
            • 273

            #20
            Originally posted by 1animal1 View Post
            Thanks Gordon... I have looked high and low at manifolds and can only see either bare manifolds, or those with the pump and blend valve attached. Are you suggesting you have something different to what's generally available?

            The only other thing I'm questioning is the pump circ, apart from an energy saving, surely the protection mechanism is a bit of a fad if it's an in use system? A pressurised system with the correct inhibitor, new or flushed shouldn't have an issue that requires such a protection mechanism? Tell me how i am wrong in my thinking
            Wasn't aware that I had. Also wasn't aware at the time that the pump normally uses that much electricity over the year. As the guys that came to install the system explained to me people would unplug the UFH motor during summer because of this and it happened quite often that the motor turned out to be stuck when they plugged it back in and as a result they would have no heating. Note these were the techies and I had already bought the system.

            I looked up the company and found a picture of a more or less similar looking manifold. The return valve in this case appears to be a passive control though and I think they may have mentioned that in my case it is thermostatic because I'm on city heating.

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            • gordonb3
              Automated Home Ninja
              • Dec 2016
              • 273

              #21
              Found some additional info on that little box bottom-left in the image. It has three main functions:
              1. it will shut down the motor when the input temperature is lower than inside the UFH (so there is no cooling after the main thermostat shuts down the boiler)
              2. it will shut down the motor when the UFH temperature reaches a set limit
              3. when the motor is switched off it will still run it for a few minutes every two days to prevent it becoming stuck

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              • 1animal1
                Automated Home Jr Member
                • Jan 2018
                • 39

                #22
                Thanks for gathering this info Gordon, very useful. Are you running this via an Evohome? From your initial description I was taking the electronics to mean a management centre such as the Honeywell ufh controller... Rather than an additional piece of hardware, which this looks like, below the motor...

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                • gordonb3
                  Automated Home Ninja
                  • Dec 2016
                  • 273

                  #23
                  Originally posted by 1animal1 View Post
                  Thanks for gathering this info Gordon, very useful. Are you running this via an Evohome? From your initial description I was taking the electronics to mean a management centre such as the Honeywell ufh controller... Rather than an additional piece of hardware, which this looks like, below the motor...
                  Well, yes and no. I have a loose HR92 lying in a cupboard that is configured in the Evohome controller to operate the UFH, so if I turn up the temperature in the living room there will be a heat demand and the BDR91 will open the main valve to the city heating (i.e. fire up the boiler). Since currently there is no actual Evohome controlled valve towards the UFH the heating will also be on in the living room if any other zone generates a heat demand.

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                  • 1animal1
                    Automated Home Jr Member
                    • Jan 2018
                    • 39

                    #24
                    Bear with me on this. If the UFH is controlled by the BDR, then surely the pump will only be running ad hoc throughout the day, therefore negating the protection and constant 'on' time causing the high electric bills. My thought is that the Honeywell will cycle it at least one every couple of hours.... Unless I'm completely off the point here? I am still at the research phase so open to being shot down

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                    • gordonb3
                      Automated Home Ninja
                      • Dec 2016
                      • 273

                      #25
                      Originally posted by 1animal1 View Post
                      Bear with me on this. If the UFH is controlled by the BDR, then surely the pump will only be running ad hoc throughout the day, therefore negating the protection and constant 'on' time causing the high electric bills. My thought is that the Honeywell will cycle it at least one every couple of hours.... Unless I'm completely off the point here? I am still at the research phase so open to being shot down
                      Ehhh... yes. If you use a BDR to control the UFH pump then you will automatically save on your electricity bill. This comes with the risk that the pump may no longer function if the heating has been off for an extended period of time, so you should have a secondary method for letting the pump run periodically. At say 3 minutes every 2 days a 60W pump will use 1kWh per year, which is seriously little money compared to needing to buy a new pump.

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                      • 1animal1
                        Automated Home Jr Member
                        • Jan 2018
                        • 39

                        #26
                        Thanks Gordon, that makes sense. I wonder if the Honeywell controller has any such function or whether it can be added as an addition...

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                        • 1animal1
                          Automated Home Jr Member
                          • Jan 2018
                          • 39

                          #27
                          Hi Gordon, update on this.... Still designing my system and collating the equipment.

                          In the interim...

                          Your point on the protection mechanism has had me thinking and searching for a similar solution - it then hit me, with the Evohome, I can simply set the system to cycle for a few minutes when ever I like, via the electronic programming! For info, Honeywell have also confirmed that their ufh controller does this automatically every 24 hours too, although I can't see any reference to this anywhere, so remain sceptical.

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                          • 1animal1
                            Automated Home Jr Member
                            • Jan 2018
                            • 39

                            #28
                            Going off the original theory of this thread. I have a slightly different set up, can someone confirm it'll work?

                            I will be going for a single zone at the start using a BDR91. However together with this, because I'm using OT, the zone valve will be always open, therefore cannot be wired into the BDR along with the pump. Question is, can the pump and a thermal actuator 230v be wired into the BDR to control the flow on and off

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