Evohome: living room getting warmer when warming other room!!??

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  • wwjd1924
    Automated Home Lurker
    • Dec 2019
    • 2

    Evohome: living room getting warmer when warming other room!!??

    I don't know what to do anymore...

    The Evohome system seems to be stupid, not able to control logically.

    Situation:
    Living room: SET: 19C, MEASURED: 19.5 VALVE % on touch display: 18%

    So I want to heat up my Study: the system is heating up the boiler.
    So far so good...


    BUT NOW the living room is also getting hotter because the HR92 does not close!
    touch display reading of living room valve remains on 18% (on HR92 valve position is 42%)

    Living room is heating up, 1 degree above SET temp of 19C and valve is not closing yet

    What is going on???

    I think I have had it with this system, I can return it until jan 31 unless someone has some suggestion??

    I do hope on some help, missing things I did not though of
    Thanks!


    DOMOTICZ SCREEN DUMP:

    here you see overshoot in STUDY when living room is heating AND overshoot in LIVING ROOM when study is heating up
    Last edited by wwjd1924; 22 December 2019, 01:36 PM. Reason: adding picture
  • chrisgare
    Automated Home Guru
    • Dec 2013
    • 182

    #2
    This sounds like normal activity to me so I'm not sure why you are concerned. I currently have all my ground floor room temperatures set to 21 degrees. Once it has achieved that temperature in the early morning, most of the radiators are either slightly on, or off, and the circulating water temperature drops back to a lower temperature that is sufficient to keep the temperature at 21 degrees. Each room is differant and it depends on the outside temperature.

    If I increase one room to a higher temperature, then the boiler is activated and the water heats up as would be expected. That higher tempertaure water flows through all the other slightly open radiators heating them and the room slightly until they turn off fully and things have settled down again.. I would expect this to happen and have no issues with it at all. Am I wrong?

    Comment

    • wwjd1924
      Automated Home Lurker
      • Dec 2019
      • 2

      #3
      Thanks for explaining! This confirms what I observed.

      But the problem for me is that the 'slightly heating' of the rooms with no heating need is at least 1 degree. that is a lot (I think) and enough for my wife to complain.
      If I don't fix this I will be banned and spent the nights in the chicken coop and it's cold out there!!

      What I don't understand is this: the system 'knows' the boiler is heating up and the living room is already 0.5C over the set-point. Radiator valve is still somewhat OPEN
      WHY would the system not close the living room valve...?

      But if that is normal behaviour than I have to return to the old situation.

      Comment

      • chrisgare
        Automated Home Guru
        • Dec 2013
        • 182

        #4
        Isn't that just as bad if it did this? Your living room temperature would then drop and it would become cold? You can't have your cake and eat it!

        Comment

        • DBMandrake
          Automated Home Legend
          • Sep 2014
          • 2361

          #5
          Originally posted by wwjd1924 View Post
          I don't know what to do anymore...

          The Evohome system seems to be stupid, not able to control logically.

          Situation:
          Living room: SET: 19C, MEASURED: 19.5 VALVE % on touch display: 18%

          So I want to heat up my Study: the system is heating up the boiler.
          So far so good...

          BUT NOW the living room is also getting hotter because the HR92 does not close!
          touch display reading of living room valve remains on 18% (on HR92 valve position is 42%)

          Living room is heating up, 1 degree above SET temp of 19C and valve is not closing yet

          What is going on???
          How long have you had the system installed ? It has a "learning" process where it learns the characteristics of your radiator valve, radiators and room characteristics. This can take a few days to a week or so to adapt, so if you've only just installed it it will not yet be optimised for your system.

          Also, what is your flow temperature set to ? If it's set too high for the weather then some interaction between rooms in inevitable if the set point changes suddenly in a different room causing the boiler flow temperature to increase suddenly.

          When you say the temperature is overshooting by one degree are you sure the room temperature is actually overshooting by this much ? Are you going by the temperature reported on the Evohome, and if so are you using the HR92 as the sensor for the zone or a separate wall sensor ?

          Or are you measuring it separately with another thermostat ? If you're going by the reading on the Evohome and using the HR92 as the sensor then it's normal for the temperature reading to fluctuate a little bit as the reading is influenced by the heat directly from the radiator, however the true room temperature will not be varying nearly much.

          For example an HR92 reporting an overshoot of one degree as measured at the HR92 itself is typically a true room overshoot of only about 0.2 degrees.

          Originally posted by wwjd1924 View Post
          Thanks for explaining! This confirms what I observed.

          But the problem for me is that the 'slightly heating' of the rooms with no heating need is at least 1 degree. that is a lot (I think) and enough for my wife to complain.
          If I don't fix this I will be banned and spent the nights in the chicken coop and it's cold out there!!

          What I don't understand is this: the system 'knows' the boiler is heating up and the living room is already 0.5C over the set-point. Radiator valve is still somewhat OPEN
          WHY would the system not close the living room valve...?

          But if that is normal behaviour than I have to return to the old situation.
          If the room needs some heat to maintain the required temperature then an HR92 will always be slightly open. If it closed completely the room would fall below the set point and need to be heated up again, causing continuous fluctuation of the temperature.

          If another zone suddenly switches on and causes the boiler flow temperature to increase a lot then the HR92 for this zone will be unaware of this. The first it will know is when the room temperature starts to overshoot slightly (usually 0.5 degrees or less) and at that time it will close the valve slightly to compensate.

          This is normal operation. If your flow temperature is excessively high or your radiators are very large you might get one degree or more overshoot - in those conditions consider reducing your boiler flow temperature a bit. A lot of people run their boiler unnecessarily hot year round and this will magnify both overshooting and interaction between rooms.
          Last edited by DBMandrake; 24 December 2019, 08:50 PM.

          Comment

          • frankmalia
            Automated Home Sr Member
            • Apr 2019
            • 63

            #6
            Hi,
            what seems to be general opinion, which I have read and noticed by monitoring the data that I log on the system. The Valves will operate/stay open up to Set point plus 1.5'C, so whether the boiler relay is on or off the HR92/80 will be open up to 100% if valve temperature is below set point +1.5'C.

            If you only have one zone demanding heat. You will find that temperature control is excellent, and setpoint will be maintained very well.

            If a second zone then demands heat this is when you can get overshoot.

            Because the second zone is demanding heat the boiler relay stays on until the second zone is at temperature then shuts off and goes into a on off cycle as per your touch screen hourly timing cycle 3/6/9/12 etc.

            Your first zone will not close until set point +1.5'C is reached. It will proportionally close up to +1.5C.

            Once both zones are at Setpoint then they will both find there happy spot for valve open %, and temperature regulation should be excellent.

            If a third zone starts demanding then the overshoots can happen again.

            See a made up table below to give example of 1 zone working and then 2 zones.



            ROOM A ROOM B
            Boiler Relay Status Set Hr92 Temp Valve Position Set Hr92 Temp Valve Position
            Room A Needing Heat On 18 16 100 15 17 0
            Room A Needing Heat On 18 16.5 100 15 17 0
            Room A Needing Heat On 18 17 100 15 17 0
            Room A Needing Heat On 18 17.5 100 15 17 0
            Room A Needing Heat On/Off 18 18 50 15 17 0
            Room A Needing Heat On/Off 18 18 40 15 17 0
            Room A Needing Heat On/Off 18 18 33 15 17 0
            Room A Needing Heat On/Off 18 18 25 15 17 0
            Valve position changing to optimise for room Room has no heat demand so valve stays closed while Room A is working as need
            Room A & B Needing Heat On 18 18 25 20 17 100
            Room A & B Needing Heat On 18 18.5 15 20 17.5 100
            Room A & B Needing Heat On 18 19 8 20 18 100
            Overshoot Period stops at Set+1.5 = Valve Closed
            Room A & B Needing Heat On 18 19.5 0 20 18.5 100
            Room A & B Needing Heat On 18 19.5 0 20 19 100
            Room A & B Needing Heat On 18 19 0 20 19.5 100
            Room A & B Needing Heat On 18 18.5 0 20 20 100
            Room A & B Needing Heat On/Off 18 18 25 20 20 25
            Room A & B Needing Heat On/Off 18 18 22 20 20 20
            Room A & B Needing Heat On/Off 18 18 15 20 20 12
            Room A & B Needing Heat On/Off 18 18 7 20 20 8

            When you have multiple zones changing setpoints at different times you can get alot of overshoots that you can notice temperature that is not desired.

            This is the system, although not perfect, it is still pretty good and alot more comfortable in the house.

            I would prefer to have the Setpoint +1.5 to be variable to my choice. lets say +0.5'C. I do not know why honeywell do this. Maybe to maximise boiler heat efficiency. Maybe to minimise the valve movements for battery life. I'm not sure and it is the worst part about evohome to me and it is annoying when you get to 1.5C overshoot when it is a zone that makes it uncomfortable.

            Still the system is still excellent as whole and better than a load of mechanical TRVs and 1 Stat to manage them all.

            This has been posted about for 5-6 years and honeywell dudes have never really never acknowledge that it is pretty crap, or given a reason for why it is +1.5'C. Lots of irate users, this should be a easy fix but they do no fix. If its to save battery life. I would happily change batteries every year if I could have a smaller differential.

            Hope this helps

            Frank

            Comment

            • DBMandrake
              Automated Home Legend
              • Sep 2014
              • 2361

              #7
              Originally posted by frankmalia View Post
              Hi,
              what seems to be general opinion, which I have read and noticed by monitoring the data that I log on the system. The Valves will operate/stay open up to Set point plus 1.5'C, so whether the boiler relay is on or off the HR92/80 will be open up to 100% if valve temperature is below set point +1.5'C.

              If you only have one zone demanding heat. You will find that temperature control is excellent, and setpoint will be maintained very well.

              If a second zone then demands heat this is when you can get overshoot.

              Because the second zone is demanding heat the boiler relay stays on until the second zone is at temperature then shuts off and goes into a on off cycle as per your touch screen hourly timing cycle 3/6/9/12 etc.

              Your first zone will not close until set point +1.5'C is reached. It will proportionally close up to +1.5C.

              Once both zones are at Setpoint then they will both find there happy spot for valve open %, and temperature regulation should be excellent.

              If a third zone starts demanding then the overshoots can happen again.
              What you say is basically true (a large set point change in another zone can cause an overshoot in unrelated zones) however it is not as bad as you describe on most Evohome installations. On my system the overshoot is rarely more than 0.5C, (measured with an independent table top thermometer) so it's not true that because the proportional zone is +/- 1.5C that the overshoot will also necessarily be 1.5C.

              The radiator controller does not require the temperature to overshoot by 1.5C before it will fully close - it can also close inside the +/- 1.5C proportional band - this depends on the previously learnt characteristics of the room and ambient conditions. It depends how much heat the room requires to maintain the set point.

              If you get large overshoots (>0.5C) in a zone when another zone comes on it almost certainly means that either your flow temperature is too high, the radiators in the zones that are overshooting are oversized, or the valve bodies don't suit the HR92 and therefore the heat into the room is difficult to control accurately.

              This means that when the flow temperature suddenly increases due to the demands of another room the room heats up so quickly that the system doesn't get time to respond - remember HR92's only make an adjustment to their valve about once every 4 minutes. Within that 4 minute period if a large radiator heats up to a very high surface temperature then it can put a lot of heat into the room that will cause an overshoot even if the HR92 closed completely on the next 4 minute interval due to the large thermal mass of the radiator. This is the essence of the problem.

              Another possible issue relating to this is mismatching of radiators in different zones. The ideal situation is that to maintain a comfortable temperature in each zone that the required flow temperature is approximately the same. This would require larger radiators in large rooms and smaller radiators in small rooms etc..

              If radiators in some zones are oversized and those in other zones are undersized you have a situation where as soon as the zone with the undersized radiator calls for heat due to a schedule change it is going to demand a high (perhaps 100%) heat demand from the boiler which will then cause other zones to overshoot.

              One way to detect this problem is to set all rooms to a similar temperature like 20C and wait until they are all stable and then have a look at the heat demands for each zone in the installer menu - if they're wildly different then there could be a radiator sizing mismatch issue. It only takes one zone with an undersized radiator that struggles to reach the set point to cause issues.

              See a made up table below to give example of 1 zone working and then 2 zones.

              [...]

              When you have multiple zones changing setpoints at different times you can get alot of overshoots that you can notice temperature that is not desired.
              The table you show above shows a clear problem with your system that needs fixing - specifically the compatibility of your valve bodies that the HR92's are attached to.

              You show Room A stabalising at 18C with a valve position of 25%, then when Room B comes on the temperature of Room A starts rising and overshoots 1.5C. This should not happen.

              The HR92 is designed with the assumption that <= 30% valve pin position means the valve is closed. Below 30% valve pin position the HR92 will not call for any heat. Please see the following graph I created some time ago to show the relationship between HR92 valve positions and heat demand called for from the boiler:



              So if your valve still lets water through the radiator significantly below a position of 30% you will have the problems you describe. This is because when Room A was the only one calling for heat it reached equilibrium with the boiler not running (25% valve position calls for 0% heat demand) however the valve is still allowing water through.

              That means when Room B calls for heat Room A is allowing water to flow through the radiator so it will continue to heat up when it shouldn't.

              What kind of valve bodies do you have, and do you use Stroke 0 or Stroke 1 mode ? If you use the default Stroke 0 mode it might be worth switching your HR92's to Stroke 1 mode. After you do this, remove the HR92's, turn the black wheel anti-clockwise and refit them to trigger a valve pin recalibration.

              After this it will take maybe a day or two for the HR92's to learn the new characteristics in Stroke 1 mode. If you're still finding that the radiators keep flowing below 30% indicated pin position you might want to consider different valve bodies.

              This is the system, although not perfect, it is still pretty good and alot more comfortable in the house.

              I would prefer to have the Setpoint +1.5 to be variable to my choice. lets say +0.5'C. I do not know why honeywell do this. Maybe to maximise boiler heat efficiency. Maybe to minimise the valve movements for battery life. I'm not sure and it is the worst part about evohome to me and it is annoying when you get to 1.5C overshoot when it is a zone that makes it uncomfortable.
              I think you're misunderstanding what the proportional band is for. If you shrink the proportional band to only +/- 0.5C you will actually cause more overshoots, because as soon as the room went 0.5C under the set point the radiator would fully open which would almost certainly cause an overshoot in response. A wider proportional band would give smoother temperature control not a narrower band.

              Your comment about minimising movements for battery life makes me think you're confusing proportional band with deadband. There is virtually no deadband in the HR92. Even a measured temperature change of about 0.1C will result in a slight movement of the motor controlling the valve position.
              Still the system is still excellent as whole and better than a load of mechanical TRVs and 1 Stat to manage them all.

              This has been posted about for 5-6 years and honeywell dudes have never really never acknowledge that it is pretty crap, or given a reason for why it is +1.5'C. Lots of irate users, this should be a easy fix but they do no fix. If its to save battery life. I would happily change batteries every year if I could have a smaller differential.
              Sorry but I really think you're misunderstanding the situation. Some interaction between zones when schedules change is unavoidable with a system like this where the flow temperature is affected by all zone heat demands, however an overshoot of 1.5C is not normal, nor does the +/- 1.5C proportional band have anything to do with this, and making it smaller would be counter productive.

              In your case I'm fairly confident that the issue you're seeing will be one or more of flow temperature too high, oversized radiators or valve bodies whose opening threshold do not match what the HR92's expect.

              While an HR92 will fit any valve with an M30x1.5 thread that doesn't mean it will work well with all of them. I actually got rid of my old peggler bulldog valves as I was having the same problem you seem to be having - they were still allowing water to flow with a valve pin position as low as 12-15% and this was upsetting the control algorithms of Evohome (which expect water to stop flowing below 30%) and causing large temperature overshoots when other zones were scheduled on very similar to what you describe.

              I don't have that issue anymore now I'm using Honeywell Valencia valves, however as I reported in another thread I did find I have to use Stroke 1 to get the best control with them as they have a very long travel pin compared to some other valve bodies.
              Last edited by DBMandrake; 3 January 2020, 02:23 PM.

              Comment

              • frankmalia
                Automated Home Sr Member
                • Apr 2019
                • 63

                #8
                Hi DBMandrake,
                Thanks for the awesome reply.

                Yeah I trust what your saying, and just describing what I am seeing to try to help a bit.

                Yes sometimes the TRVs stay closed when another is heating, but 9 out of 10 time the open up to +1.5'C

                The 30% thing is interesting, As most of my if not all my radiatiors only close when 0% valve position on HR92.

                But I also have room with Honeywell Valencia TRV(brand new) The overshoots on the initial temperature setpoint change from low to higher setpoint is quite bad +2.5 sometimes, but ok when running at a constant setpoint.

                1.jpg

                I also have a room non honeywell TRV that is up and down all the time, this room I am looking at changing for Valencia TRV. As if your less than 30% should be closed then I have issues here.



                2.jpg

                Flow Temperature? Is this my boiler temperature or is it difference between input and output pipes of radiator? My boiler is 75'C at the moment, I turned it up week or so to try things, think it made it worse. I have dropped it to 65'C

                My system has been learning 2-3 months now.


                I agree that flow temperature too high, oversized radiators or valve bodies whose opening threshold do not match what the HR92's expect is the pro. I will be changing some valves eventually.

                I kinda cannot agree with the valve being open up to +1.5'C, that's not correct because valve only goes to zero at +1.5 90% of the time. But that 30% thing may be the issue. If you say less 30% valve thinks its closed. But if it thinks its closed, why would it drive down to 0% at +1.5'C, if it thought it was close. A smaller proportional window has got to be better on the plus side of the set point.

                Going to try the valve stroke setting on the my one valencia valve, as I thought would not need it setting

                Also trying to throttle some of the troublesome zones.

                I will keep you posted, and thanks for your input
                Last edited by frankmalia; 3 January 2020, 11:58 PM.

                Comment

                • frankmalia
                  Automated Home Sr Member
                  • Apr 2019
                  • 63

                  #9
                  Checked the honeywell valencia trv and valve was 13% position and definetly passing water across it.

                  Set valve stroke to Full 1 and disconnected TRV and Reconnected to calibrate again.

                  So about the less than 30% being closed this one only closes fully at 0% I think.

                  Comment

                  • DBMandrake
                    Automated Home Legend
                    • Sep 2014
                    • 2361

                    #10
                    Originally posted by frankmalia View Post
                    The 30% thing is interesting, As most of my if not all my radiatiors only close when 0% valve position on HR92.
                    0% can't be right. To test this I would do the following:

                    1) Turn down the zone on test to 2C below ambient and wait for the radiator panel to go cold.
                    2) Turn up some other zone (not an adjacent room to avoid heat leakage through a doorway) ~3C above ambinet to cause a continous 100% heat demand from the boiler for the duration of the test
                    2) Slowly increment the set point on the HR92 by 0.5C adjusting directly on the HR92, wait a couple of minutes each time to see if the radaitor gets warm if not, increase by another 0.5C and wait again etc.. at each step after you hear the motor finish turning go to setting 10 to see what the highest valve pin position is where it remains cold, and the lowest position is where the radiator starts to heat up. The threshold will be between these two points.

                    Ideally the threshold should be between 25-35% for the system to work properly.

                    If it's a long way from 30% you will see the following symptoms:

                    >40% - heat demand may cause the boiler to cycle on when no radiators are getting hot, because the HR92 is calling for heat from the boiler but no water is flowing through the radiator.

                    <20% - a room which is at equilibrium with a very low heat demand will overshoot in temperature when another zone triggers a high heat demand - what you are seeing.

                    When you look at the graph in my previous post its easy to see that the HR92 assumes ~30% is the opening threshold of the valve - below that it doesn't call for heat, from about 30% to 70% the valve allows progressively more water flow and calls for more heat from the boiler (higher flow temperature) doubling the effect of the valve position since it affects both water flow and flow temperature, then from 70% to 100% it is assumed that the valve is flowing fully (turning a tap on the last couple of turns often doesn't make a change) so in this situation all the temperature modulation comes from the change in heat demand - hence why the slope from 70-100% is roughly twice as steep.

                    It's a clever design when you think about it, given what the system has to work with. Keep in mind that the Stroke setting changes the way the valve pin position is calibrated, both the closing force and the amount of travel between closed and open, so the opening threshold in percent for the exact same valve can be very different in Stroke 0 and 1 modes, hence why it is worth trying both modes.

                    I've taken lots of opening threshold measurements on my system both with my old Pegler Bulldog valves and again after replacing them with Honeywell Valencia valves, and they behaved totally different.

                    When I first got the bulldog valves (actually they were in the system 6 months before Evohome was installed) it seemed to work OK in Stroke 0 mode, with no real issues however after about a year I started seeing a lot of overshoots when other rooms changed set point, exactly as you describe.

                    It was particularly bad in the main bedroom - which is set to 16C overnight, and in winter has to run intermittently or even continously at a very low surface temperature to keep the room warm - in the morning when all the downstairs radiators are scheduled on the bedroom would then overshoot 2C or more - uncomfortable enough to wake us up as I'm quite sensitive to room temperature when sleeping. And yes, the Bedroom does have an oversized radiator, which exacerbates the problem.

                    This is when I started investigating the problem in detail and looking at the valve pin position of the bedroom radiator during a temperature overshoot - and like you I found that the room was approx 1.5C over temperature and the radiator panel was still very hot and I could still hear flow through the radiator. This was occuring when the valve position reported was only 18% and it didn't completely close until it got to about 12%.

                    As far as the HR92 is concerned 18% is a closed valve and it is not calling for any heat so it's job is done, however in response to the temperature continuing to exceed the set point it will eventually close the valve down to 0% but not until it's too late.

                    I found that if I initated a recalibration of the valve (remove the HR92, turn the black wheel anti-clockwise, refit and let it cycle) that the calibration would change so that the valve closed at about 30% - and everything seemed fine, however a day or two later the calibration would be out again and it would not be closing until about 15% and the problem returned.

                    In fact I noticed that if I manually cycled the valve through its full range of operation by setting the set point high and low and high again etc that every time it reached the two limits it would change the calibration slightly (it tweaks the calibration every time it reaches the limits if necessary) and with every cycle the calibration would go out and after only a few full cycles it was back to 15% again.

                    After replacing the valves my opinion is that the valve bodies had deteriorated - I'm not entirely sure if they were seizing up, or whether the rubber gaskets had gone hard in response to flushing solution (or just age/poor quality rubber etc) but the pins were quite corroded inside after I removed them and did not move smoothly.

                    I had the opposite issue with my Valencia valves where they wouldn't start flowing until an indicated 60% pin position which of course caused the boiler to cycle on without the radiator getting hot. Eventually I solved the issue by adjusting the balancing insert fully out (so it's just touching) and setting the HR92 to Stroke 1 mode, now they work very well and the threshold is very close to a reported 30%. In my opinion the integrated balancing insert should not be used with an HR92! Use the lockshield valve to balance instead...

                    For the full details of that escapade, read the following longish thread!



                    Flow Temperature? Is this my boiler temperature or is it difference between input and output pipes of radiator? My boiler is 75'C at the moment, I turned it up week or so to try things, think it made it worse. I have dropped it to 65'C

                    My system has been learning 2-3 months now.
                    At this time of year my flow temperature is 70C, however I have many old radiators that by todays standards are undersized, (non-convectors etc) mixed with modern convector radiators. If you have more modern radiators you might want to be running at a lower temperature. Easy way to tell - set the flow temperature lower than you think it should be, if any rooms can't make their set point at all or in a reasonable time, turn it up a bit!
                    I kinda cannot agree with the valve being open up to +1.5'C, that's not correct because valve only goes to zero at +1.5 90% of the time. But that 30% thing may be the issue. If you say less 30% valve thinks its closed. But if it thinks its closed, why would it drive down to 0% at +1.5'C, if it thought it was close. A smaller proportional window has got to be better on the plus side of the set point.
                    I know you're sceptical that other people don't see the huge overshoots you're reporting, so here is the last 24 hours of all of my zones with a little bit of commentary about what the zones themselves are like. A couple have overshoots but most do not:



                    The bathroom radiator is a bit of a worst case scenario and is showing "overshoots" as much as 3C. However to keep this in perspective, the temperature is being measured on the HR92, which is right in the corner of the room behind the door hinge, so when the door is partly open the HR92 is blocked into a very small space and can't sense the room temperature correctly, the radiator typically has towels on it, sometimes covering the HR92, and there is the heat source of the shower/bath itself that often warms up the room. In short, I wouldn't expect any kind of accurate temperature regulation in these circumstances, at least without a remote wall thermostat, which isn't justified for a bathroom.



                    The kitchen radiator is also a bit of a worst case scenario - the radiator is mounted under a counter top flanked immediately by kitchen cabinets, thus the HR92 sensing the temperature is right in the corner of this recess and can't sense the room temperature properly. Overshoots of 1-2C occur, at least as measured at the HR92 - it's doubtful the true room temperature is overshooting this much. I'm also confident that if I fitted a remote wall thermostat to the room the temperature control would be good without overshoot. I haven't done so mainly for lack of a good available wall surface to mount it on that isn't directly over a heat source.



                    The hallway has a fairly large (for a hallway) panel and the Evotouch itself is the temperature sensor for the zone on a wall mount on the opposing wall. Temperature control here is excellent with no overshoot, however the room itself sometimes does overshoot if doors are left open from warmer rooms, as can be seen in the above graph.

                    Continued in next post due to post size limit...
                    Last edited by DBMandrake; 4 January 2020, 02:43 PM.

                    Comment

                    • DBMandrake
                      Automated Home Legend
                      • Sep 2014
                      • 2361

                      #11


                      The living room has three panels mounted in a bay window and a DTS92 as sensor on another wall. Temperature regulation is excellent and there is no overshoot at all.



                      The dining room has two radiators - a long radiator under a very large window and a small one on the opposing wall. The HR92 on the long one (exterior wall) is the sensor for the zone. Very minimal overshoot here. +/- 0.5C which is typical when sensing from an HR92. I plan to fit a DTS92 in this room soon as the HR92 is sometimes obscured by toys and naturally doesn't control the room temperature as well in those situations!



                      The study has a long panel under the window and measures the temperature at the HR92. This room also suffers from obstructions near the HR92 sometimes and the radiator itself is a bit sick. Overshoot is minimal however. I'm considering fitting a DTS92 in this room as well because it often under reports the temperature of the room when there are obstructions near the HR92.



                      The main bedroom has a somewhat oversized radiator under a loft window, with a DTS92 at the head of the bed on another wall. This room is subject to the window being open different amounts (or not at all) on different nights so the system has to adapt to this. This room had severe overshoot in the mornings with my old TRV valve bodies but as you can see is now OK despite the somewhat oversized radiator.

                      Continued in next post due to 5 image limit (!)
                      Last edited by DBMandrake; 4 January 2020, 02:44 PM.

                      Comment

                      • DBMandrake
                        Automated Home Legend
                        • Sep 2014
                        • 2361

                        #12


                        This is our son's room and also has a somewhat oversized radiator under a loft window and a DTS92 on another wall near his bed. The room is an awkward L shape so a bit of a challenge to regulate the temperature of, however the system does a pretty good job, usually keeping it within +/- 1C as reported at the DTS92, and it does not overshoot significantly when other zones come on in the morning. (Perhaps 0.5C at the most)

                        I believe the +/- 1C variations are due to this being the only radiator on most nights, causing the heat demand to fall below the minimum 10% (1 minute on time) the Evotouch requires to call for heat from the boiler. As a result the temperature sometimes has to fall significantly below the set point before the boiler comes back on. I suspect that Opentherm control would avoid this issue, so if I ever replace my geriatric boiler I'll be trying to get one with Opentherm for this and other reasons.

                        Hopefully that gives an example of real world data on a system that is not experiencing the overshoots you see.

                        Going to try the valve stroke setting on the my one valencia valve, as I thought would not need it setting
                        Have a look at my valencia thread - it's a long read but despite others disagreeing I found that I had to use Stroke 1 for satisfactory results, and also not use the integrated balancing insert - if you try to balance the radiator with the integrated insert you add a large deadband to the HR92's control range as you are basically restricting how far the pin can come out when you wind the balancer down. I found it much better to wind the balancer out until it was nearly loose, then balance the radiators the traditional way with the lockshield valves, allowing the HR92 to maintain a full control range.

                        Also trying to throttle some of the troublesome zones.

                        I will keep you posted, and thanks for your input
                        Is your system well balanced in terms of lockshield valves etc ? If not it might be worth having a look at that.


                        Originally posted by frankmalia View Post
                        Checked the honeywell valencia trv and valve was 13% position and definetly passing water across it.

                        Set valve stroke to Full 1 and disconnected TRV and Reconnected to calibrate again.

                        So about the less than 30% being closed this one only closes fully at 0% I think.
                        I'm surprised your HR92 was reporting 13% and still flowing on a Valencia. On mine in Stroke 0 mode they start flowing at 40-60% (!) and in Stroke 1 mode about 30%.
                        Last edited by DBMandrake; 4 January 2020, 02:48 PM.

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                        • frankmalia
                          Automated Home Sr Member
                          • Apr 2019
                          • 63

                          #13
                          DBMandrake
                          Another great response and had a play with Valencia after reading your other thread.

                          Ok, correction to my statement my Valencia is opening some where above 17%(close) and definitely at 43%(open), could not get valve to go to 30ish% with temperature conditions and setpoints. Played today when measuring pipe temperatures. To detect hot water flow. Unfortunately the Valencia valve radiator sounds like its flowing when it was not, never realised, this is the only radiators that makes noise like this when not flowing, must be coming from below pipework.
                          Your correct some of my older radiators, flow below 30% valve position, one flowing at 11% position, checked with temp gauges and touch.
                          Some of these, yeah I am seeing the +1.5 on these ones.

                          Looking at you nice graphs, what do you use for that?
                          I’m a little less concerned as you are getting overshoots. More than 1.5 on your graphs sometimes. Like you said the room temp is ok, if you measure it with separate temp gauge away from HR92 - but I use the only constant reading I have which is the HR92.
                          My hallway is one of the better rooms for minimal overshoots, like yours. Large space for heat to dissipate, plus flow of heat upstairs.

                          Couple of the rooms have obstacles close that may have any effect. But I think like you say it’s the TRVs open below 30% spool position.
                          The fact that Honeywell do this is crap because the system is meant to be able work on other TRV valves, they have a large compatibility list. System should be 0 %, valve rammed closed. Then anything else above this considered a calibrated and learned open position.
                          Again this still a great system that is better than others. But the fact you buy a system that is sold like its has this potential is not good. 8 of TRVs are new ish not Honeywell(different manufactures, drayton/bulldog etc) 1 is a Valencia. The 30% close/open thing is not good, if dodgy on certain valves.

                          Anyway I have the kitchen and a couple of bedrooms to look at changing valves for Valencia for a little project in a couple of months time.

                          Thanks for you help and info.

                          Frank

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                          • DBMandrake
                            Automated Home Legend
                            • Sep 2014
                            • 2361

                            #14
                            Originally posted by frankmalia View Post
                            DBMandrake
                            Ok, correction to my statement my Valencia is opening some where above 17%(close) and definitely at 43%(open), could not get valve to go to 30ish% with temperature conditions and setpoints.
                            To get closer figures it just takes a bit of patience, waiting while it makes gradual changes in response to room temperature changes and then rechecking option 10.

                            I checked my Living room radiator yesterday and confirmed that the valve was flowing slightly at 37% valve position indicated and was warm, and at 27% it was definitely completely stopped, so I'm happy with that. That was also one of the radiators which had problems with overshoots due to not shutting down the flow properly with my old valve bodies.
                            Played today when measuring pipe temperatures. To detect hot water flow. Unfortunately the Valencia valve radiator sounds like its flowing when it was not, never realised, this is the only radiators that makes noise like this when not flowing, must be coming from below pipework.
                            I have the same issue in our bedroom - our radiator branches off the lines that go to our son's bedroom and as his radiator is set to a higher night time temperature it tends to run during a winter night when ours does not - ours hisses slightly and sounds like it running but the radiator is stone cold and the room above the set point so the noise must be transmitted from the pipes behind the walls to the radiator panel...
                            Your correct some of my older radiators, flow below 30% valve position, one flowing at 11% position, checked with temp gauges and touch.
                            Some of these, yeah I am seeing the +1.5 on these ones.
                            Still flowing at 11% is definitely going to cause overshoots, no doubt about it, that's even worse than the ones I was originally having problems with. You would want to see the threshold between 25-35% for optimal operation and minimum interaction between zones. If you can solve that you should be able to solve or greatly mitigate the problem. Did you try enabling Stroke 1 mode and letting the valve re-calibrate yet ? If the valve is a bit stiffer than average (strong spring tension on the pin) the HR92 may have trouble closing it and may not calibrate well.

                            The calibration procedure winds the pin down until a certain amount of force is reached (I presume by measuring the current drawn by the DC motor) and this point is considered to be 0%, with 100% counting back a certain number of turns from there. This builds in some assumption about the amount of force a valve takes to sufficiently compress the sealing washer, and therefore how far the pin will move back out before the washer un-compresses and water starts to flow past the washer.

                            If the spring in the valve is unusually strong (or the valve is starting to seize slightly due to corrosion of the pin, like mine were) they require more force to operate, this can cause the calibrate routine to find the fully down position incorrectly as when it thinks it is fully compressing the washer it is really just finding high resistance from the spring or the pin itself. This means the washer is barely compressed at "0%" and it only needs to move say 10-15% before it starts flowing. In extreme cases it may not be able to close the valve at all and it may leak all the time.

                            One thing Stroke 1 mode does is increase the force exerted when finding the closed position during the calibration, as a result 0% will be pushing down harder on the pin and compressing the washer more, therefore the opening point where it starts to flow will occur at a higher numeric percentage, and it will more reliably calibrate on a stiff valve. If the reason for the stiffness is friction from a corroded pin this may still cause erratic calibration problems where it initially calibrates correctly but over time the calibration goes out as it keeps trying to re-calibrate during use. I think this is what was happening on my old valves.
                            Looking at you nice graphs, what do you use for that?
                            They're from Linux based graphing software Munin using the Evohome-munin plugin.

                            I run it on a Raspberry Pi. The outdoor temperature is normally taken from an online service (weather.com I think) however I've modified the script to receive my outdoor weather station using an RTL-USB receiver to get more accurate and realtime outdoor temperatures.
                            I’m a little less concerned as you are getting overshoots. More than 1.5 on your graphs sometimes. Like you said the room temp is ok, if you measure it with separate temp gauge away from HR92 - but I use the only constant reading I have which is the HR92.
                            My hallway is one of the better rooms for minimal overshoots, like yours. Large space for heat to dissipate, plus flow of heat upstairs.
                            In the rooms I am seeing big overshoots in (kitchen and bathroom) this is a result of the placement of the HR92 and not a true representation of the room temperature. If I was using a remote DTS92 sensor in these zones I don't think I would see an issue there.

                            When an HR92 is the temperature sensor its important not to assume that overshoots or fluctuations necessarily show changes in the true room temperature as localised heating from the radiator can cause larger swings that don't really exist in the room. If you see large overshoots with a remote sensor then yes, the overshoot is real.
                            Couple of the rooms have obstacles close that may have any effect. But I think like you say it’s the TRVs open below 30% spool position.
                            The fact that Honeywell do this is crap because the system is meant to be able work on other TRV valves, they have a large compatibility list. System should be 0 %, valve rammed closed. Then anything else above this considered a calibrated and learned open position.
                            Only shutting at 0% would not work very well for proportional control. Although water shouldn't be flowing below 30%, the range from 0-30% position is still part of the proportional band from a control perspective. So if the room is slightly over temperature it may drop to 25%, if its significantly over it may drop to 20% and so on. How much below 30% it is allows it to track how far it is from equilibrium.

                            Comment

                            • DBMandrake
                              Automated Home Legend
                              • Sep 2014
                              • 2361

                              #15
                              Again this still a great system that is better than others. But the fact you buy a system that is sold like its has this potential is not good. 8 of TRVs are new ish not Honeywell(different manufactures, drayton/bulldog etc) 1 is a Valencia. The 30% close/open thing is not good, if dodgy on certain valves.
                              To be fair to Honeywell, after first encountering these problems and studying them and how the system works I've thought a lot about the issues of trying to proportionally control the water flow of a radiator and juggle that with sending a heat demand to the boiler, and concluded it's a very difficult problem to solve, and on two fronts.

                              One is the interaction between zones. On the one hand you obviously don't want the boiler at maximum flow temperature all the time with a valve barely open to put out a little bit of heat from a single bedroom radiator on a cool night, as that would be hugely inefficient with 99% of the flow going back through the ABV and a lot of heat loss from the boiler casing and nearby piping etc.

                              So under a low demand situation you want a large(ish) water flow through the radiator (and little or none through the ABV) but a low flow temperature so that the total heat into the room is low. In this circumstance you modulate the heat into the room by varying the flow temperature (directly by OpenTherm or indirectly via TPI) and not so much by water flow.

                              The Evohome system naturally does this because it takes a fairly high valve position to generate a significant heat demand - even a heat demand of only 20% requires a valve position of 55% - well beyond the 30% where the valve should start to flow water.

                              However when any zone needs a high demand the flow temperature needs to rise to meet the demand of the most demanding zone, and at that point zones with low demand must then close their valves down significantly to prevent an overshoot and modulate their heat output by controlling the water flow only.

                              The HR92's are unfortunately not aware that some other zone has requested a higher flow temperature, so their first clue that something has happened is when the room temperature starts to overshoot and they will start to close a bit. This can take up to 4 minutes and in that time a lot of latent heat can be stored in a large panel radiator that will be radiated even after the valve closes. If the valve calibration is good the overshoot will typically be only about 0.5C though.

                              So one theoretical improvement that could be made to a multi-zone system is for the controller to also send the aggregate heat demand that is going to the boiler back to all the individual radiator controllers.

                              That way an HR92 could be "forewarned" that the flow temperature is about to shoot up and roughly by how much, and by using a lookup table it could probably preemptively throttle back its valve position in anticipation to prevent an overshoot even happening at all. And by comparing it's own heat demand to the aggregate one it could tell whether it was currently the "controlling" zone or whether some other zone was controlling the heat demand (by having a higher demand) and make decisions based on that.

                              Unfortunately I strongly doubt there would be any way to retrofit that into the Rameses protocol nor the current HR92's, (which don't even have over the air firmware update ability) so we would be talking about an all new system. However there is a second problem with this preemptive throttling - for it work well the HR92 would need to know precisely at what position the valve starts flowing, otherwise its preemptive action could just as easily lead to the room dipping below the setpoint instead of overshooting...

                              And that comes to the second problem - calibration of the valve. How does it figure out at exactly what point any given valve body starts flowing water ? The short answer is it can't... it doesn't have enough information to deduce that. All it has available is a force vs distance calibration which it uses to try to find the fully closed position of the valve, and a temperature sensor.

                              Could it slowly increase the opening and wait for the temperature to rise, then open it a bit more and wait again and then guess that is the opening point when it sees a rise ? Maybe, with some clever heuristics... but it could equally get very confused by changes in heat demand from other zones or someone closing a door etc...

                              Could it measure the temperature of the valve body itself from the water flowing through it ? Maybe - that solves the problem of unrelated air temperature changes but you still have the zone interaction problem, and now you get a very different result depending on whether the HR92 is on the flow or return side as the flow pipe will heat quickly but the return pipe can be delayed many minutes on a large radiator.

                              Apart from the preemptive messaging of system wide heat demand back to TRV's I think Honeywell is already doing as much as they could given that they are trying to be compatible with existing TRV valve bodies.

                              To go the next step up you would need to incorporate a calibrated water valve as part of the TRV itself instead of them being separate. In that you could potentially put both a flow rate sensor and a temperature sensor and that would give the TRV controller a LOT more information to go on. It would know exactly at what point the valve opened and what temperature of water was flowing through. (Although it would probably need a setting to tell it whether it was on flow or return side so it could adjust its algorithms)

                              The question is, is all this extra over engineering of a fully integrated TRV/valve body worth it for slightly better control ? I'd say probably not, and the market wouldn't go for it if it meant a drain down to replace the valve bodies on every installation...

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