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

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  • JohnDoe
    Automated Home Jr Member
    • Jan 2017
    • 18

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

    Hello all,

    New here.

    I'm having a fresh central heating and hot water installation done (all new pipework, new boiler, new rads, new unvented cylinder) at my new place which has a cellar, ground floor, first floor and second floor. There are 4 zone valves (1 for HW, 1 for cellar/ground, 1 for first floor and 1 for second floor).

    My installer is competent but has not installed EvoHome before. He is going to call Honeywell for advice but I thought I'd ask here what the best way is for him to wire the zone valves?

    Secondly, some of the house (second floor) may be unused for some time and I may want all the radiators there switched off, save for the hall way one, perhaps - should I get HR92s for this floor?

    Thirdly, I don't want to have specific control of every single radiator (say bathrooms). How does this work with EvoHome which I understand has a limit of 12 zones?

    Thanks in advance.
  • paulockenden
    Automated Home Legend
    • Apr 2015
    • 1719

    #2
    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.

    Comment

    • HenGus
      Automated Home Legend
      • May 2014
      • 1001

      #3
      A starter for you and your installer should be the Evohome Installation Guide and this website:



      I will leave it to others with more knowledge of Evohome and multi motorised valves to comment on your proposed set up. Suffice it to say, that if HR92s are fitted to all radiators, no motorised valves (except for HW) are required. HR92s are grouped into zones with one HR92 acting as the zone temperature sensor ( a separate remote sensor can be used instead). I do have the standard 'S' plan with 12 zones. When a zone demands heat, the valve opens and the boiler comes on. When no heat is demanded, the valve closes and the boiler heat shuts off.

      PS: I should have added that Evohome has to be installed fully in accordance with the installation guide. In particular, minimum separation distances for the various components are essential if you don't want to spend your life trying to resolve communications faults. I would also suggest that you get your installer to fit HR92 compatible TRV bodies (honeywell Valencia)
      Last edited by HenGus; 22 January 2017, 10:45 AM.

      Comment

      • DBMandrake
        Automated Home Legend
        • Sep 2014
        • 2361

        #4
        Evohome is really designed to have control over every radiator using an HR92 - anything else is a compromise in some way or the other.

        It sounds like you weren't planning to get any HR92's ?

        You are limited to 12 zones per controller but there is no hard limit on the number of HR92's. So if you have multiple radiators per room that keeps the total number of zones at 12 or less that is not an issue. It's also possible to group multiple rooms into a single zone using "multi-room zone" mode, where those rooms share the same schedule.

        It might be the case for example that you could group multiple bathrooms together to follow the same schedule thus "bathrooms" counts as a single zone. Or Children's bedrooms might be another one.

        Some information that would help understand your situation better - how many rooms do you have with radiators in them, and what is the total number of radiators ?

        (Edit: that was freaky - three replies within a minute!)
        Last edited by DBMandrake; 22 January 2017, 10:46 AM.

        Comment

        • DBMandrake
          Automated Home Legend
          • Sep 2014
          • 2361

          #5
          Originally posted by paulockenden View Post
          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.
          Good catch - I hadn't really noticed 4 floors were involved. Depending on the construction of the building its even possible that no one single location will reach all devices on all four "floors", and that two controllers on different floors might be necessary from a signal point of view - so signal testing should really be done before lots of money is spent.

          This would solve the issue of having too many zones for one controller, but complicate the boiler control and wiring. One controller would have to be in charge of hot water and some of the heating zones while the other would be in charge of the other heating zones.

          For that to work well you might need two heating zone valves (in addition to the hot water zone valve) to separate them so that each controller could call for CH heat via its own zone valve. (With both zone valves calling for heat from the boiler) Otherwise there would be interaction between the two controllers where one controller calling for an increase in heat from the boiler would cause the zones under the control of the other controller to overshoot.

          Wiring and zoning for this would be a little bit complicated so would be best left to a Honeywell specialist to figure out if you did go the two controller route.

          Comment

          • paulockenden
            Automated Home Legend
            • Apr 2015
            • 1719

            #6
            I'd imagine a good installer would bring along a controller, an HR92, and a BDR91 and use them to do a site survey prior to doing anything.

            Needless to say, mine didn't....

            P.

            Comment

            • MrB
              Automated Home Sr Member
              • Oct 2015
              • 80

              #7
              Had same scenario just over a year ago with new boiler, pipes, rads etc. Big house sideways, not up/down.
              Made the mistake of thinking Evohome is an add-on. It's not. It's core and the boss.

              Had plumbers put in 3 Zone Valves - HW, Up Heating, Down Heating. Wrong - hindsight is wonderful isn't it,

              Most plumbers (or heartng engineers) have years doing standard stuff and that's how their brain is wired. Evo is, simply put, "what it really should be".
              i
              You need just 2 Zone Valves - HW and Heating.
              Good quality constant pressure pump.
              Evo TRVs on every Rad - grouped as needed (as above) (These are the "real" Zones for Evohome).

              I have Evo controlling Valves and Valves controlling Boiler - Boiler controls pump as is needed by IT.

              Sytem works a treat - all rooms exacly where we want them and there is always sufficient HW.

              And for icing on the cake get a Amazon Echo and use Alexa to give even more control - I can say "set office hallway to 21" , "set Bedrooms to 21" or "set downstairs heating to 21" - this would give you ALL the flexibility you describe. ie: "set first floor off"
              Last edited by MrB; 22 January 2017, 12:22 PM.

              Comment

              • bruce_miranda
                Automated Home Legend
                • Jul 2014
                • 2307

                #8
                Originally posted by MrB View Post
                You need just 2 Zone Valves - HW and Heating.
                Good quality constant pressure pump.
                Evo TRVs on every Rad - grouped as needed (as above) (These are the "real" Zones for Evohome).
                Actually just 1 Zone Valve for HW, and TRV controllers on all radiators.

                Comment

                • DBMandrake
                  Automated Home Legend
                  • Sep 2014
                  • 2361

                  #9
                  Originally posted by bruce_miranda View Post
                  Actually just 1 Zone Valve for HW, and TRV controllers on all radiators.
                  This can result in room temperature overshoots when hot water demand activates though, due to a sudden increase in flow temperature that the partially open HR92's were not expecting - see my S-Plan thread for my workaround for that in a two zone valve configuration...

                  Comment

                  • HenGus
                    Automated Home Legend
                    • May 2014
                    • 1001

                    #10
                    Originally posted by DBMandrake View Post
                    This can result in room temperature overshoots when hot water demand activates though, due to a sudden increase in flow temperature that the partially open HR92's were not expecting - see my S-Plan thread for my workaround for that in a two zone valve configuration...
                    Good point. That said, the two installers that I have been talking to about a boiler replacement looked at my system and tried to suggest that it would be far simpler just to leave the 'S' plan configuration as is, and not worry about the burst of hot water around the CH system.

                    Comment

                    • MrB
                      Automated Home Sr Member
                      • Oct 2015
                      • 80

                      #11
                      ** good point on the only 1 Valve - that was something I remember from the beginning now.. the pipe runs around the different Rad groups are non-connected parallel pipes which are bridged when the TRV opens. So the Motorized Valve is redundant.

                      BUT, here's a very good reason to have a Valve on the heating side..

                      As I said above somewhere - my system is about 14 months old and all the supplied batteries in the Evo TRVs are starting to fail. There was one TRV I ignored when the Controller gave a Low Battery warning. The batteries in the TRV completely emptied and the TRV screen was blank, BUT the valve had been left partially opened so it heated all the time there was any pump pressure as there was no shut-off.

                      So without that main Motorised Valve shutting off the heating pipe's it would have been heating everywhere on that pipe run and the Rad whenever the Boiler was on and the Pump was running, and the pipe runs going to, and returning, from that Rad would be radiating heat as well.

                      So the heating M.V. acted as a partial fail safe. Still pretty good though as during the day there's a lot of HW requests and not much heating requests.

                      Comment

                      • bruce_miranda
                        Automated Home Legend
                        • Jul 2014
                        • 2307

                        #12
                        Originally posted by DBMandrake View Post
                        This can result in room temperature overshoots when hot water demand activates though, due to a sudden increase in flow temperature that the partially open HR92's were not expecting - see my S-Plan thread for my workaround for that in a two zone valve configuration...
                        But this would even happen with 2 valves one for HW and CH. Or you can implement HW priority via a single BDR91.

                        Comment

                        • JohnDoe
                          Automated Home Jr Member
                          • Jan 2017
                          • 18

                          #13
                          Thanks all for the replies.. just trying to take it all in.

                          I've counted 23 radiators (including towel rails) - that's a lot of HR92s... quick pricing on google means I am looking at probably around 2k for all the bits (assuming one HR92 on every single radiator including towel rail).

                          I already have 4 zones valves which are as yet unused so I suppose I could sell a couple of those to save some cash, however, given the cost, I am now just considering if something like 1 x Nest per zone would be more cost effective. Granted, I wouldn't have granular control per room (only per floor), but I could just switchoff the TRVs in unused rooms?

                          I do like the EvoHome system, if I don't have HR92s on the towel rails, what are the implications of this?

                          Is there any way of 'extending' the signal? My original idea was to have all the 'gubbins' in the cellar along with the boiler and cylinder, with the main control unit being on the ground floor. Could there be an issue with the main control unit communicating with the HR92s on say the second floor?

                          Hmm.. decisions, decisons!


                          Radiators:

                          Cellar - likely 1 radiator

                          Ground floor
                          Front Room 1 - 1 radiator
                          Front Room 2 - 1 radiator
                          Dining Room - 2 radiators
                          Hallway - 2 radiators
                          Shower room 1 - 1 towel rail
                          Utility - 1 radiator
                          Kitchen - 1 radiator

                          First floor
                          Hallway - 1 radiator
                          Bed 1 - 1 radiator
                          Bed 2 - 1 radiator
                          Bed 3 - 1 radiator
                          Shower room - 1 towel rail
                          Bathroom - 1 towel rail

                          Second Floor
                          Hallway - 1 radiator
                          Bed 4 - 2 radiators
                          Bed 5 - 1 radiator
                          Bed 6 - 1 radiator
                          Bed 7 - 1 radiator
                          Shower room - 1 radiator
                          Last edited by JohnDoe; 22 January 2017, 07:38 PM. Reason: add radiators to ground floor

                          Comment

                          • DBMandrake
                            Automated Home Legend
                            • Sep 2014
                            • 2361

                            #14
                            Originally posted by bruce_miranda View Post
                            But this would even happen with 2 valves one for HW and CH.
                            To a much lesser degree, because it can control the water flow to the radiators separately from the hot water cylinder.

                            Total heat going to radiators is controlled by a combination of three factors - boiler duty cycle, heating zone valve duty cycle, and individual HR92 valve openings.

                            Say you have only a hot water zone valve and no heating zone valve, hot water is currently off, radiators are in the proportional band maintaining constant temperatures. Boiler duty cycle might be 30% resulting in a low average flow temperature (say 45) and HR92's are open a fair way. (say 60%)

                            Then hot water demand starts - for the entire time hot water is heating the boiler duty cycle goes to 100% and at first water continues to flow continuously through all HR92's as before, but the flow temperature climbs to 70. (or whatever your maximum is for hot water demand)

                            The radiators that were flowing but were luke warm now get really hot within a few minutes, and probably reach 70 degrees before the system even detects any rise in room temperature. (Temperatures are only sampled every 4 minutes at most) By the time the system detects a rise in room temperature its too late - the radiators are scalding hot and will remain that way long after the valve is closed and the room will overshoot by a degree or so by the time the radiators cool down.

                            With a heating zone valve in the same circumstances the valve would only let water flow through the radiators for 30% of the time and thus greatly restrict the temperature rise of the radiators during the hot water demand.
                            Or you can implement HW priority via a single BDR91.
                            You could, if you don't mind radiators getting cold during hot water reheating.

                            Also you still need two 2 port zone valves or a diverter valve to achieve HW priority - and you then have to come up with a way to not have the heating zone valve running all the time when the system (and therefore hot water) is off.

                            Hence the scheme I came up with my S-Plan thread which I think solves all the problems at once, and is quite simple in component count.

                            Comment

                            • HenGus
                              Automated Home Legend
                              • May 2014
                              • 1001

                              #15
                              @John Doe. Nest 3 is an option but so are 3 Evohome controllers. There isn't much difference in price. The Evohome controller has a built in sensor so it will work in a zone with no HR92s or in a zone with HR92s.

                              Comment

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