Completely new heating install, best way to configure for EvoHome?

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  • bruce_miranda
    Automated Home Legend
    • Jul 2014
    • 2307

    #76
    Evohome assumes you need one BDR91 for the HW and the other to fire the Boiler as a Boiler Relay. If you have a true S plan then you will land up with 3 BDR91s. One for HW, one for CH and one for Boiler. Ofcourse you could choose to use an OT bridge instead of a Boiler Relay and then have the two BDR control the HW and CH valves only.

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    • DBMandrake
      Automated Home Legend
      • Sep 2014
      • 2361

      #77
      Originally posted by bruce_miranda View Post
      Evohome assumes you need one BDR91 for the HW and the other to fire the Boiler as a Boiler Relay.
      No it doesn't - the most common S-Plan configuration with Evohome has two BDR91's - one for the HW zone valve and one for the CH zone valve. The boiler is fired using the orange wires of both zones valves not directly, so there is no boiler relay in this configuration.

      If you only have a hot water zone valve and no heating zone valve (in which case it's not really an S-Plan or Y-Plan system) then yes you can configure the two BDR91's as hot water zone valve and boiler relay instead, and let the HR92's prevent heating during hot water demand, provided all radiators have HR92's.
      If you have a true S plan then you will land up with 3 BDR91s. One for HW, one for CH and one for Boiler.
      This three relay configuration is a second option for S-Plan/Y-Plan - and is the one I use. It's more complicated but it does give some additional flexibility over firing the boiler from the zone valves or not having a heating zone valve.
      Last edited by DBMandrake; 5 February 2017, 09:56 PM.

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      • bruce_miranda
        Automated Home Legend
        • Jul 2014
        • 2307

        #78
        The reason I said Evohome assumes one BDR to work the HW and one to fire the boiler is because that's how it comes configured in the box. To use the Boiler relay to work the CH valve instead you need to unbind it as the Boiler relay and rebind it as the CH zone valve relay.
        Evohome expects all your radiators to have HR92s with no separate CH zone valve.

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        • dty
          Automated Home Ninja
          • Aug 2016
          • 489

          #79
          Originally posted by bruce_miranda View Post
          The reason I said Evohome assumes one BDR to work the HW and one to fire the boiler is because that's how it comes configured in the box. To use the Boiler relay to work the CH valve instead you need to unbind it as the Boiler relay and rebind it as the CH zone valve relay.
          Evohome expects all your radiators to have HR92s with no separate CH zone valve.
          That's how mine works (due to piping layout, primarily), but it's described as an "alternative layout" in the installation guide.

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          • Bovrilelles
            Automated Home Lurker
            • Nov 2018
            • 8

            #80
            Originally posted by paulockenden View Post
            I know this isn't what you want to hear, but Evohome works best when you give it control of everything. I think that when spending the amount you must be, it's daft to skimp on a couple of hundred quid for additional HR92s.

            However, if you do that, a couple of things to note:

            1 - You won't actually need the four zone valves (so perhaps a saving can be made there to pay for the HR92s?).
            2 - You'll probably need to have the controller on one of the middle floors, to get a reliable signal to the top floor and your basement. Ideally somewhere in the middle of that floor too, rather than on an external wall.

            As for the 12 zone limit, you can put several HR92s (or even rooms) into the same zone. So you could have a 'bathrooms' zone, for example, or 'second floor'.

            I'm sure others will have observations too....

            P.
            Does this mean the combination of EvoHome BR91 and HR92s on a S Plan dual valve system will effectively zone?

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            • DBMandrake
              Automated Home Legend
              • Sep 2014
              • 2361

              #81
              Originally posted by Bovrilelles View Post
              Does this mean the combination of EvoHome BR91 and HR92s on a S Plan dual valve system will effectively zone?
              Can you restate the question ? By "S Plan dual valve system" do you just mean a standard S plan system with one hot water zone valve and one heating zone valve ?

              Or are you talking about an S-Plan plus system with more than one heating zone valve, for example to different floors ?

              As for zoning - if you fit HR92's to all radiators then your house is fully zoned (regardless of whether you have any heating zone valves) as every zone on the controller can be scheduled and controlled independently and all are capable of calling for heat from the boiler. EG There is no one specific zone that always has to be heating to get heat elsewhere, such as a room stat in a hallway on a traditional system where if that hallway isn't calling for heat no other rooms can get heat. (One of my pet peeves with a traditional single thermostat and manual TRV's system)

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              • Bovrilelles
                Automated Home Lurker
                • Nov 2018
                • 8

                #82
                Definitely S Plan rather than S plan plus unfortunately. Roger that re fitting TRVs to all to accommodate zoning.

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                • DBMandrake
                  Automated Home Legend
                  • Sep 2014
                  • 2361

                  #83
                  S-plan plus is redundant with Evohome as the TRV’s do the zoning for you. You’d just end up wiring all heating zone valves to come on together anyway as evohome does not have the ability (or need) to independently control multiple heating zone valves for HR92 radiator controller zones.

                  In fact it’s possible to configure an S-plan system without any heating zone valves with evohome (just one for hot water) as long as all radiators have HR92’s, although there are some minor disadvantages to doing that if your boiler boosts flow temperature for hot water reheating.
                  Last edited by DBMandrake; 22 November 2018, 07:22 PM.

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                  • Bovrilelles
                    Automated Home Lurker
                    • Nov 2018
                    • 8

                    #84
                    Originally posted by DBMandrake View Post
                    S-plan plus is redundant with Evohome as the TRV’s do the zoning for you. You’d just end up wiring all heating zone valves to come on together anyway as evohome does not have the ability (or need) to independently control multiple heating zone valves for HR92 radiator controller zones.

                    In fact it’s possible to configure an S-plan system without any heating zone valves with evohome (just one for hot water) as long as all radiators have HR92’s, although there are some minor disadvantages to doing that if your boiler boosts flow temperature for hot water reheating.
                    Great news! Had a plumber here today (fitting towel rails, magna-clean and bigger pump) who (knows nothing about EvoHome) and told me it was ‘pointless as I needed 12 individual valves coming back to the boiler from each rad to zone it’. It’s tough trying to explain to an ‘expert’ that they might be wrong!! I just wish I had an EvoHome installation specialist nearby (which I don’t!) so thank god for this forum!!!
                    Boiler been offline for the duration of the day and now not sure controller is communicating with BDR91. Do you know how I can do a factory re-set and re-bind to my controller? (In layman’s terms?!)

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