Evohome Opentherm Boiler decision and set up

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

    Evening chaps

    Gus, I can't see that this is anything to do with the Atag, the boiler is a slave to the Evo OT module which in turn is a slave to the Evo Controller - the system is a CH system primarily as per the Honeywell OT instructions, when HW is requested, power shuts the CH valve and opens the HW valve in tandem (which sounds exactly as yours was). The fact that the system is now working without issue, because it's programmed for the HW to not coincide with a high CH demand, suggests Evohome gives priority I would have thought, possibly delaying the HW triggering. Unless I'm misunderstanding what you are suggesting?

    Upon thinking further, the additional UFH system under a further normally closed valve would work independent of both the HW and CH, as this would run off the main 22mm branch from the boiler and not after the CH/HW valves - initially powering the pump/valve via a BDR91 (single zone for now) given that it has it's own blending valve it would meter down the hot water when the HW is on, and request what it needs as per a normal zone. This does beg the same question though, would the Evohome treat this effective BDR zone valve like it does the HR92's when requesting heat or delay the opening of the UFH valve when the normal CH circuit is drawing a high demand .

    Comment

    • mtmcgavock
      Automated Home Legend
      • Mar 2017
      • 507

      Originally posted by 1animal1 View Post
      Evening chaps

      Gus, I can't see that this is anything to do with the Atag, the boiler is a slave to the Evo OT module which in turn is a slave to the Evo Controller - the system is a CH system primarily as per the Honeywell OT instructions, when HW is requested, power shuts the CH valve and opens the HW valve in tandem (which sounds exactly as yours was). The fact that the system is now working without issue, because it's programmed for the HW to not coincide with a high CH demand, suggests Evohome gives priority I would have thought, possibly delaying the HW triggering. Unless I'm misunderstanding what you are suggesting?

      Upon thinking further, the additional UFH system under a further normally closed valve would work independent of both the HW and CH, as this would run off the main 22mm branch from the boiler and not after the CH/HW valves - initially powering the pump/valve via a BDR91 (single zone for now) given that it has it's own blending valve it would meter down the hot water when the HW is on, and request what it needs as per a normal zone. This does beg the same question though, would the Evohome treat this effective BDR zone valve like it does the HR92's when requesting heat or delay the opening of the UFH valve when the normal CH circuit is drawing a high demand .
      I think you're misunderstanding on how OT works with EvoHome and how Hot Water Priority works with EvoHome. Evohome has no support for Hot Water Priority as a feature. This is why it has to be done using zone valves and wiring. When you have a hot water demand EvoHome requests 100% flow temperature, no matter what. If there's a demand for CH, it'll still request 100% demand. It won't prioritise Central heating over hot water.

      If your valves are working as they should there should be no reason why the hot water doesn't recover quickly in the morning, as there will be no other demand on the system (As the CH Valve should have shut down).

      In terms of the UFH this should have again a NO valve on so that closes on HW demand, giving priority to the HW circuit. Then on the manifold there will be actuators for each zone, controlled by either a BDR91 or HCC80 depending on which route you go down. The EvoHome controller will then send a demand to the OT receiver at your boiler.

      Comment

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

        Thanks MTM

        I get that EHome treats the hot water as a zone (BDR91) and requests max heat, as you wouldn't want anything less for HW. My concern is born out of what was happening prior to me changing the settings. You'd think 1hr 30mins would be enough to heat the water despite CH being on high for the morning warm up - this in isolation suggests i have a valve issue. Adjusting the time and extending an extra hour prior to the high heat demand, and my HW now working exactly as it should, suggests my valves are all good and it's possibly the EHome controller wizardry?

        For my UFH, I'll be speccing a 6 port manifold which i thought would be working off a NC valve? Opening when the stat signals the BDR to open the valve. I will only be using the first 2 ports for the first two piped areas (open plan), working off the same stat initially (the Evo controller). If I decide the 2 areas need a stat each, I'll then get the HCC80 ordered together with the actuators, otherwise this can wait until zone 3 comes into play. Surely a NO valve is prevalent when i have the HCC80 with actuators?

        Comment

        • mtmcgavock
          Automated Home Legend
          • Mar 2017
          • 507

          Originally posted by 1animal1 View Post
          I get that EHome treats the hot water as a zone (BDR91) and requests max heat, as you wouldn't want anything less for HW. My concern is born out of what was happening prior to me changing the settings. You'd think 1hr 30mins would be enough to heat the water despite CH being on high for the morning warm up - this in isolation suggests i have a valve issue. Adjusting the time and extending an extra hour prior to the high heat demand, and my HW now working exactly as it should, suggests my valves are all good and it's possibly the EHome controller wizardry?
          It could suggest a number of issues -
          - Evohome isn't requesting 100% flow temperature on HW demand. The easiest way to test this would be to turn the heating off and put HW on and see if the boiler reaches TMax.
          - Your valves aren't working as they should, extending the time has then allowed the cylinder to reheat over a longer period of time. For instance if your boiler is only 18kw, some Unvented cylinder coils can be up to 24kw on a 200/250L cylinder. If your hot water and heating is going at the same time it'll take longer to reheat.

          You also have to take into consideration about the hot water. You only reheat it every other day? So usually it is probably reheating from cold. My 170L cylinder from cold takes 45 minutes to reheat on a 14kw coil, compared to a recovery of 24minutes on a 70% draw off. So if you're reheating a larger cylinder, and then drawing off at the same time (E.g. Showers in the morning) it is going to take longer to reheat.


          Originally posted by 1animal1 View Post
          For my UFH, I'll be speccing a 6 port manifold which i thought would be working off a NC valve? Opening when the stat signals the BDR to open the valve. I will only be using the first 2 ports for the first two piped areas (open plan), working off the same stat initially (the Evo controller). If I decide the 2 areas need a stat each, I'll then get the HCC80 ordered together with the actuators, otherwise this can wait until zone 3 comes into play. Surely a NO valve is prevalent when i have the HCC80 with actuators?
          No the idea of the NO valve would be to cut off the Underfloor when a Hot Water demand is on, exactly like it does on the radiator circuit. The downside to this means you'd need actuators, however they're only cheap and still can be controlled by just a BDR91 (You don't need a HCC80)

          You could actually do it using a NC valve however you'd have to get a wire from your HW BDR91 back to the UFH BDR91. And maybe i'm just complicating matters

          In simple terms, you need to switch off the flow to the UFH when there's a HW demand. Otherwise you haven't got HW priority.

          Comment

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

            Hi MTM

            I know for certain that the boiler is requesting 100%... The boiler is an ATAG IS32, so plenty big enough to feed my 250L cylinder. That aside, the way my system is set up means that when the HW is requested and the signal is sent to the HW BDR, this closes to NO CH valve and opens the NC HW valve, so it should have complete priority. Before, on the previous timings, the hot water didn't heat at all - this again makes me think that the Evohome wasn't activating the HW BDR - it was set at the same time every second day and each day is should have heated up mirrored the next. Bizarre eh?

            For ref, hot water draw off is only normal kitchen and bathroom use for now - shower to be added soon (currently on electric shower).

            UFH - Thanks for the tips! The UFH NC/NO,i suppose if i specced a NC, it would have to be changed to NO when i upgrade to the HCC80 anyway. The UFH valve will be located at the other side of the cylinder to the boiler and other valves, where my 22mm hot/cold branches terminate after being routed around the back of the cylinder. So the UFH BDR/Pump/manifold & Valve will all be in the same area (Spur to be added) - what you are saying, is wire the BDR to the pump and actuators, and the NO valve to the original terminal block in the exact config as the NO on the CH system?

            Actuators powered by the BDR - will these work like the HR92's? And which ones would i spec, i note two sizes (manifold dependent?) and NO/NC too.. presume NC.

            Comment

            • mtmcgavock
              Automated Home Legend
              • Mar 2017
              • 507

              Originally posted by 1animal1 View Post
              UFH - Thanks for the tips! The UFH NC/NO,i suppose if i specced a NC, it would have to be changed to NO when i upgrade to the HCC80 anyway. The UFH valve will be located at the other side of the cylinder to the boiler and other valves, where my 22mm hot/cold branches terminate after being routed around the back of the cylinder. So the UFH BDR/Pump/manifold & Valve will all be in the same area (Spur to be added) - what you are saying, is wire the BDR to the pump and actuators, and the NO valve to the original terminal block in the exact config as the NO on the CH system?

              Actuators powered by the BDR - will these work like the HR92's? And which ones would i spec, i note two sizes (manifold dependent?) and NO/NC too.. presume NC.
              In a nut shell, yes. You've got it.

              Actuators, two wire ones will be fine if you're just doing one zone. You can get 4 wire ones which have their own microswitches, if you wanted to control more areas without a HCC80. But again, won't complicate things here.

              No they don't work like HR92s, they're either open or shut when using a BDR91.

              Comment

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

                So with the actuators, you can spec MT4 or 8's https://theevohomeshop.co.uk/22-unde...ating-controls , i had read that this was the sizings inside 4mm and 8mm?

                Also, this chap in this thread is suggesting that i lose a certain protection mechanism if not using the HSS80 https://www.wordpress-1219309-438749...-Evohome/page2

                To confirm, when/if i upgrade to the HSS80, i will need the 2 wire versions?

                Comment

                • mtmcgavock
                  Automated Home Legend
                  • Mar 2017
                  • 507

                  Originally posted by 1animal1 View Post
                  So with the actuators, you can spec MT4 or 8's https://theevohomeshop.co.uk/22-unde...ating-controls , i had read that this was the sizings inside 4mm and 8mm?

                  Also, this chap in this thread is suggesting that i lose a certain protection mechanism if not using the HSS80 https://www.wordpress-1219309-438749...-Evohome/page2

                  To confirm, when/if i upgrade to the HSS80, i will need the 2 wire versions?
                  That'll depend on your manifold. You generally would get the make that would be for the manifold.

                  There's no issues with using a BDR91 to control underfloor.

                  The 2 wire ones are the ones you'll need but the 4 wire will also work.

                  Comment

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

                    Thanks again for this, I've been trawling Google to find as much info as possible. Any pointers on manifold brands and material? (been looking at stainless polypipe) I had also assumed Grundfos was the way to go pump wise....

                    Comment

                    • mtmcgavock
                      Automated Home Legend
                      • Mar 2017
                      • 507

                      Originally posted by 1animal1 View Post
                      Thanks again for this, I've been trawling Google to find as much info as possible. Any pointers on manifold brands and material? (been looking at stainless polypipe) I had also assumed Grundfos was the way to go pump wise....
                      Speedfit or Polypipe. Tend to fit more Polypipe, however Speedfit is just as good. Both come with a Grunfos pump in the Mixing valve/pump packs.

                      Comment

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

                        Perfect, thanks MTM. I'm going to be lifting the t&g boards, fitting 75mm kingspan between the joists, then fitting the aluminium panels with the pipe grooves, then refitting the t&g boards. Thinking of running the 16mm PEX pipes which seem quite a bit cheaper than 15mm.... Presume minimal difference other than cost.

                        For the wiring, the NO valve gets wired in parallel to the NO valve on the CH. The pump and actuators wired to the BDR... Simple as that?

                        Comment

                        • mtmcgavock
                          Automated Home Legend
                          • Mar 2017
                          • 507

                          Originally posted by 1animal1 View Post
                          Perfect, thanks MTM. I'm going to be lifting the t&g boards, fitting 75mm kingspan between the joists, then fitting the aluminium panels with the pipe grooves, then refitting the t&g boards. Thinking of running the 16mm PEX pipes which seem quite a bit cheaper than 15mm.... Presume minimal difference other than cost.

                          For the wiring, the NO valve gets wired in parallel to the NO valve on the CH. The pump and actuators wired to the BDR... Simple as that?
                          Personally i'd stick with the 15mm pipe from either Speedfit or Polypipe. The odd system that I have done with 16mm I haven't been impressed with, along with the fact you wouldn't be able to use a Polypipe or Speedfit manifold.

                          Can't put tongue and groove back, you need to board with chipboard and glue the joints. I'd then recommend self levelling on top depending on your finished floor. Tongue and groove you'll have too many joints for expansion and contraction and you will get movement. This will affect your finished floor.

                          If it's one zone only, then yes you are correct!

                          Comment

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

                            No you're kidding! About the t&g.... I have come from a house using chip board and hated it, especially in a kitchen where it could get wet. Is this the only way around this? Final finish will be laminate boards

                            Comment

                            • mtmcgavock
                              Automated Home Legend
                              • Mar 2017
                              • 507

                              Originally posted by 1animal1 View Post
                              No you're kidding! About the t&g.... I have come from a house using chip board and hated it, especially in a kitchen where it could get wet. Is this the only way around this? Final finish will be laminate boards
                              Well I wouldn't be putting T&G floorboards back. You other option would be to put plywood down, however you'd need the special underfloor plywood stuff which is a fortune (Due to the layers separating under heat).

                              Comment

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

                                I think you're talking marine ply, yeah I'll skip that at £50 a sheet... Although I'd be able to park the car in the kitchen with the strength of it

                                I'll have to go down the chip board route in that case, presume 18mm t&g boards, bigger the better for less joints...

                                Comment

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