Honeywell Valencia problems

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  • blowlamp
    Automated Home Sr Member
    • Apr 2017
    • 98

    #16
    It seems logical to me to have valve bodies that have hard rubber washers that give low hysteresis to the TRV (HR92 in this case) to work with. It's counter productive to have a large, undetermined % of the movement wasted in decompressing a soft washer.

    The other point is that a small radiator will need a tiny adjustment of the pin to maintain a steady room temperature, in comparision to a large radiator. I think it would help if Evohome asked for radiator size information at installation time, so a suitable scaling value could be applied to valve movement. Though maybe this is taken care of during the learning period.

    I believe the purpose of the lockshield is to allow just enough hot water to flow through the radiator that lets it heat the room under the most severe weather conditions. Flow needs to be restricted within individual radiators to ensure hot water is directed to all other radiators that may be calling for heat, without leaving any starved for water.



    Martin.

    Comment

    • DBMandrake
      Automated Home Legend
      • Sep 2014
      • 2361

      #17
      Originally posted by blowlamp View Post
      It seems logical to me to have valve bodies that have hard rubber washers that give low hysteresis to the TRV (HR92 in this case) to work with. It's counter productive to have a large, undetermined % of the movement wasted in decompressing a soft washer.
      I tend to agree. With the Valencia in Stroke 1 mode 25% of the available calibrated pin travel is used compressing the washer and not varying the water flow, I consider that acceptable as there needs to be some compression to ensure that when it fully closes it really does close water tight despite any dimensional variations, and also calls for heat start at about 30% pin movement.

      However in Stoke 0 mode well over 60% of the calibrated pin travel is spent before the washer even starts to lift off the seat and allow water flow. This seems totally wrong to me, and this was not the case on the bulldog valves which where approximately 30% travel in Stroke 0 mode before starting to flow and maybe 15% in Stroke 1 mode. (In this case Stroke 0 was more suitable)

      The HR92's calibration process determines the closed position empirically - when you first fit the head to the valve and lock it, the cycle mode that runs basically winds the valve pin down until a set amount of resistance is "felt" by the motor, no doubt determined by measuring the current drawn by the motor.

      This is then considered to be the "closed" or 0% reference for pin movement. Obviously as you compress a washer it starts off easy then more and more force is required to compress it further. Because it's compressible there isn't a sudden increase in required force to detect "closed" so there has to be some arbitrary threshold of force chosen that is considered closed. This threshold differs between Stroke 0 and 1, with 1 applying more force during calibration.

      The problem is, the more compressible the washer is the more pin travel there will be between the calibrated 0% position based on force and the washer actually beginning to lift off the seat. The softer the washer the more lost travel. So built into the calibration routine of the HR92 is an assumption of washer compressibility to help it estimate at what point the water will start to flow. The reality is an HR92 has no idea at what point water is really starting to flow, so this is one of the challenges it has to work with.

      As an HR92 starts calling for heat >30% pin travel its pretty clear that the built in design assumption is that 30% of the calibrated pin travel is lost to washer compression and is where it's expecting the valve to start allowing water to flow, so any large deviation from this will have side effects on the ability to control the radiator temperature and call for heat at the correct time.

      For whatever reason, Honeywell's own flagship valve body doesn't seem to line up with the design expectation of the HR92's calibration routine - at least in Stroke 0 mode.

      Stroke 1 mode changes several things...

      1) Increased torque when closing - this affects the calibration of the 0% closed position - it will be pushed down a bit harder and further when closed than Stroke 0.
      2) Increased pin travel between 0% and 100% - in Stroke 1 mode it will turn the full 2 1/4 revolutions that the black wheel is typically capable of, in stroke 0 mode it will only turn about 1 1/4 turns from the fully closed position, remembering that the fully closed position will also be further up due to the different calibration. So essentially Stroke 1 will move further in both directions compared to Stroke 0.
      3) The motor turns faster.

      The reason why the opening threshold calibration changes is simply a matter of scaling - 0 to 100% pin position in Stroke 1 is more revolutions of the wheel and more pin travel, so the fixed amount of travel consumed by the washer compression becomes a smaller overall percentage of the total available movement, which brings the opening threshold down in percentage, while the percentage opening to heat demand curve remains the same.

      For best compatibility with a variety of valves more than the two Stroke settings we have now would have been ideal as there is a big jump between the two settings, but I guess they didn't want to complicate things too much.

      The other point is that a small radiator will need a tiny adjustment of the pin to maintain a steady room temperature, in comparision to a large radiator. I think it would help if Evohome asked for radiator size information at installation time, so a suitable scaling value could be applied to valve movement. Though maybe this is taken care of during the learning period.
      Actually I think it's the reverse - a large radiator, for a given room, needs a smaller more precise adjustment to keep a steady temperature, because the amount of heat it can put into the room, and quickly, from opening the valve too much by mistake is a lot more than a smaller radiator. A larger radiator has a larger thermal mass/storage so the penalty for getting it wrong is much greater because even when you realise the mistake and close the valve the thermal mass will put a lot of heat into the room after the water flow stops, causing an overshoot. A small radiator will give a smaller overshoot as a penalty for a mistake.

      If we assume that an HR92 is a self tuning PID controller (which I believe it is, by graphing and observing its behaviour closely over the last 2+ years) then I would hope that it can self tune the proportional coefficient. It definitely tunes the differential coefficient heuristically as when you make a large change to the response time of a room (such as covering a radiator with a towel, or removing it) you can see the step response overshoot or undershoot the first time after that but then very quickly - after only one or two cycles of set point changes it will adapt and start hitting it's targets again. So it definitely learns and adapts to factors like room response time and tendency to over or undershoot.

      I think the biggest problem with making small accurate adjustments is "stiction" of the valve body itself, and that's one of the main reasons I replaced my old valve bodies. The pins in them had corroded internally, and there were clear signs of stiction in their operation.

      After comparing with the Valencia the old valves had a larger diameter pin with a metal to metal sliding surface (large static friction) vs a small diameter pin with a plastic sleeve on the Valencia (low static friction) and another unexpected difference is that the return spring on the Valencia is a LOT stronger than the bulldogs ever were. So strong in fact that when you remove the HR92 from the base the black wheel actually spins itself instantly to the fully up position - something that never happened on the old valves.

      On the old valves the combination of increased friction and a weak return spring would introduce some unwanted hysteresis into the control of the pin position by the HR92. It would have to turn the motor a significant amount before the pin would actually move, especially in the unwinding direction, as the spring was not strong enough to immediately overcome the friction when the HR92's wheel moved away from the pin slightly.

      This added hysteresis would cause oscillations in the room temperature as it was unable to make a sufficiently small adjustment to the valve position, so it would keep overshooting one way then the other. This was my theory before changing the valve bodies and I'm pleased to report that it seems to have been experimentally confirmed.

      The combination of lower movement friction and much stronger return spring probably eliminates the hysteresis that was there in pin movement before - now the tiniest movement of the motor in the HR92 translates directly to a tiny movement of the pin.

      The result is that my rooms that originally did not overshoot 2 years ago but started overshooting as the bulldog valves deteriorated, are once again not overshoot at all, and maintaining a very steady temperature, and those rooms that due to HR92 sensor placement can't avoid a little bit of overshoot (like the kitchen radiator under a counter top) are overshooting less than half as much as they were before. So clearly there is finer control available to the HR92 with the new valve bodies...
      Last edited by DBMandrake; 24 September 2018, 02:02 PM.

      Comment

      • DBMandrake
        Automated Home Legend
        • Sep 2014
        • 2361

        #18
        I believe the purpose of the lockshield is to allow just enough hot water to flow through the radiator that lets it heat the room under the most severe weather conditions. Flow needs to be restricted within individual radiators to ensure hot water is directed to all other radiators that may be calling for heat, without leaving any starved for water.
        I have a different view on the purpose of balancing with lockshield valves than many. Many say that it's all about getting the 11C (or 20C these days) drop across radiators for efficiency. But as I don't have a condensing boiler that doesn't apply to me.

        In my opinion the purpose of balancing, condensing boiler or not is to equalise the flow resistance of every radiator branch so that no radiators can steal flow from others if they are all on at once. Depending on the length and diameter of runs to each radiator and the radiators themselves, they will all have a different flow resistance, when multiple radiators are open that means that those with low flow resistance will steal a lot more flow than those with high flow resistance.

        The difference can be enough that with all radiators on a couple of radiators close to the boiler can get hot quickly when far away radiators may hardly get hot at all as they are starved of flow due to the water preferring to follow the easiest paths.

        So with this as a goal you would start with the radiator that already has the most flow resistance (long or skinny pipes etc) and leave that lockshield fully open, that becomes your baseline. Then you would adjust the ones with lower flow resistance to increase their flow resistance to match.

        In theory once balanced this way, on a cold start all radiators should heat up at about the same rate with no radiator starved or significantly straggling - the water is equally happy to flow into all the different branches at about the same rate, and no matter what combination of radiators are open, they all get their fair share.

        This will introduce some temperature drop across the radiators of course but the key thing here is that if the drop is not sufficient (not at least 11C or whatever you choose) then turn down the pump speed/pressure, do not close the lockshields any further. There should be at least one radiator in the house whose lockshield valve is fully open otherwise you are just making the pump work harder for no reason.

        Another issue with adjusting them purely by measuring temperature drop is that temperature drop depends on heat loss, but for a given water flow rate a longer/large radiator or one with better fins is clearly going to lose more heat to the room, so going by temperature drop alone you would tend to open the lockshield more, which may starve a small, further away radiator.

        Just my opinion though...
        Last edited by DBMandrake; 24 September 2018, 02:05 PM.

        Comment

        • paulockenden
          Automated Home Legend
          • Apr 2015
          • 1719

          #19
          The thing is, despite all this talk about pin travel, valve positions etc., for many of us the HR92+Valencia combination works well.

          It's important not to ignore that.

          P.

          Comment

          • DBMandrake
            Automated Home Legend
            • Sep 2014
            • 2361

            #20
            Originally posted by paulockenden View Post
            The thing is, despite all this talk about pin travel, valve positions etc., for many of us the HR92+Valencia combination works well.

            It's important not to ignore that.
            Well there's working, and then there's working optimally. I didn't say it doesn't work at all in Stroke 0 with a Valencia, just that it's a long way from optimal. And I had the same issues on all 7 operational radiators, so I doubt it's a faulty valve or HR92.

            Depending on how closely you monitor your system and what your zone schedules are like you may not necessarily notice obvious problems, especially if you were a non-technical house owner.

            For example calling for heat long before the radiator opens probably wouldn't be noticed if there are always multiple zones configured to be on at once. I suspect I'm in the minority having a schedule that has a single zone on for significant periods of the day.

            And unless I got up to go look at the boiler relay light or check in the boiler cupboard I may not realise that the boiler was churning away during a period when only that one zone should be on and the radiator was cold to the touch... I do actually have the boiler relay on the kitchen wall near the fridge, so I am generally somewhat aware of whether the boiler is running or not, so if I see it on when I don't think it should be I tend to investigate.

            I imagine that many people have their BDR91's hidden away in a cupboard with their boiler so would not be aware it was on without specifically looking in the cupboard, and Honeywell steadfastly refuse to add any sort of heat demand information to the home screen of the Evotouch that might alert people to unexpected boiler firing. I wonder why...

            Then you only have to look at the symptoms that can result from the issue I've discovered to see if other people have independently reported the same issues prior to me:

            1) Zones calling for heat from the boiler while the radiators remain cold - check. I replied to a thread about this not that long ago, suggested Stroke 1 mode to the poster and surprise surprise, it fixed the problem for them. I don't recall if they had Valencia's or some other valves but I'll see if I can find the thread to check. As this calibration issue probably depends mainly on pin length and compressibility of the rubber washer it's feasible there are valves other than the Valencia that could suffer from the same issue in Stroke 0 mode.

            2) Unusually high OpenTherm boiler flow temperatures requested in situations where radiators are not very hot and not much heat is needed - check. I remember reading multiple threads about this in the last few months. I'll see if I can dig them up to investigate further.

            3) Excessive interaction between different zones, in particular when a 2nd zone comes online at 100% when the first zone was maintaining a constant temperature with a low heat output - check. I was having this problem myself and have certainly seen it reported many times.

            So consider this thread to be a public service announcement of what I've discovered, and that potentially some systems are not running nearly as well as they could be, particularly in regards to unnecessarily high flow temperatures and calls for heat to the boiler when a radiator is not flowing. It's applicable specifically to the Valencia, but its quite possible there are other 3rd party valves that are similarly affected.

            Those with a more technical interest in their system may want to investigate further to see if it is working optimally or not.
            Last edited by DBMandrake; 24 September 2018, 02:36 PM.

            Comment

            • paulockenden
              Automated Home Legend
              • Apr 2015
              • 1719

              #21
              My main bedroom is our first zone to come on. I hear the TRV open, and then a short time after I hear the pipework start to 'click' as it expands, so I'm pretty sure that hot water is flowing as soon as it's needed.

              Did you give your HR92 time to learn the new valve? I'm wondering whether, during the two week (or so we're told) learning process, the start and end points of the pin movement actually change? So what you're seeing as 75% might be 30% in a couple of weeks time?

              Not saying it will, just suggesting that this could explain what you are seeing.

              Of course, if you HAVE given it time to learn then just ignore me!

              P.

              Comment

              • DBMandrake
                Automated Home Legend
                • Sep 2014
                • 2361

                #22
                Originally posted by paulockenden View Post
                My main bedroom is our first zone to come on. I hear the TRV open, and then a short time after I hear the pipework start to 'click' as it expands, so I'm pretty sure that hot water is flowing as soon as it's needed.
                I would assume in that scenario there is a sudden jump in set point from a night time setback to a daytime temperature ? If the set point jumps past the current temperature by at least 1.5C the HR92 will just go from 0% pin position straight to 100% and call for a 100% heat demand as well.

                So if the night time set point is 15C and morning wake up time is 20C, if the actual temperature is anything below 18.5C when the set point changes it will just go straight to 100% and you won't see any delay in the initial boiler firing.

                The scenario I'm painting is more where you have a fixed set point and the room temperature gradually falls below it - say 21C set point but due to a warm day the room is 22C and the boiler is off. As the temperature slowly drops in the evening by the time it gets to about 20.5C the HR92 will generate enough heat demand (10%) at a pin position of approximately 35% to cause the boiler to fire, but the valve wasn't flowing until 75% pin position. This would require the temperature to fall to say 20C.

                So the whole time the room is gradually falling in temperature from 20.5C to 20C, which might be half an hour or even an hour in the afternoon/evening, the boiler is cheerfully heating and pumping hot water around the ABV loop and the radiator remains cold. This is not just theoretical it's what actually happened to me.

                The following morning when it was set to come on to 21C by 7am, two hours after that the room was still 20C, yet the radiator was cold and once again the boiler was running with the flow temperature pegged at it's 65C flow temperature. I checked the pin position which was 74%, and the reported heat demand on the controller from the zone was 42% despite the cold radiator. That's the point where I really decided "no, that's not right" and started the whole investigation that lead to this thread...

                Did you give your HR92 time to learn the new valve? I'm wondering whether, during the two week (or so we're told) learning process, the start and end points of the pin movement actually change? So what you're seeing as 75% might be 30% in a couple of weeks time?

                Not saying it will, just suggesting that this could explain what you are seeing.
                Fair comment.

                No, I didn't give it two weeks to adapt, but it did get 48 hours, after which time it showed no signs of improving it's valve position calibration. I wasn't keen on leaving it for days/weeks where it was running the boiler without heating the radiator. Our gas bill is already high enough.

                The long term adaption you're referring to I believe is more about the tuning of the PID controller to learn the response time of the whole radiator/room system. So learning not to overshoot/undershoot etc. Yes, this does take a few days and in fact even after changing stroke mode it has been undershooting slightly in the living room the last couple of days but it is now coming right. This adaption process can't be sped up.

                However calibration of the pin position happens a lot quicker - it just takes a few full open/close cycles and can be hastened by repeatedly setting a low set point and high set point and giving the valve time to respond - the pin calibration does "settle in" a little bit in the first few cycles, especially in stroke 1 mode where it is trying to operate over the full available travel. But once you've cycled the valve through it's full range of movement a few times the pin calibration doesn't seem to change any further - I checked that again to be sure on the spare valve/HR92 that I have.

                If you weren't to manually cycle the set point up and down a few times then yes, in a typical schedule it would take a few days for the pin calibration to settle in just because it does take 3 or 4 full pin cycles to do so.

                I can't be certain of course, but I'm reasonably sure that the pin calibration problem I was seeing would not have gone away by itself if I'd left it a couple of weeks. The set point would have eventually been reached and maintained but only by running the valve near the upper end of its pin position with a high heat demand from the boiler and plenty of occasions of calling for heat when not needed.
                Last edited by DBMandrake; 24 September 2018, 07:41 PM.

                Comment

                • rotor
                  Automated Home Guru
                  • Aug 2015
                  • 124

                  #23
                  Surely there has to be a fault? The HR92 has no idea what the valve is doing "under the bonnet", it just knows that anti-clockwise = more heat, and clockwise = less heat. If it's demanding heat while having the pin in a position where water is unable to flow, then it has got things wrong, i.e. it hasn't learned the behaviour of the valve. As for the difference between the two stroke types, that is not something that has ever seemed a problem to me (all my radiators have Valencias), as I suspect the range of movement is usually absolutely tiny. I only hear the HR92 motors going continuously (more than a second or so) at the beginning or end of a session, and when wide open (i.e. at the beginning of a session) any given radiator is piping hot, so there's no flow restriction worth worrying about in the "wide-open" position. If the HR92 is able to sit (fully screwed on) where it is just beginning to depress the pin, then it should have more than enough room in both directions in the normal stroke configuration.

                  I've had a couple of problems with my Valencias getting stuck closed, so could it be that?

                  Comment

                  • DBMandrake
                    Automated Home Legend
                    • Sep 2014
                    • 2361

                    #24
                    Originally posted by rotor View Post
                    Surely there has to be a fault?
                    You mean I have 7 faulty HR92's and/or 7 faulty brand new Valencia's ? Seems unlikely.
                    The HR92 has no idea what the valve is doing "under the bonnet", it just knows that anti-clockwise = more heat, and clockwise = less heat. If it's demanding heat while having the pin in a position where water is unable to flow, then it has got things wrong, i.e. it hasn't learned the behaviour of the valve.
                    But how could it learn that ? How would it actually know at what pin position the valve starts flowing when the only feedback it has at all is the flimsiest of indirect evidence of a change in temperature in the room ? The answer is, it simply can't know.

                    I posted this graph in another thread a while back where I empirically derived the relationship between valve pin position and heat demand sent to the controller. This relationship is fixed and does not change with stroke mode, nor does it learn or adapt over time or differ from one HR92 to another. It's always the same on all the HR92's I tested.



                    It's pretty clear from the graph that there is an implicit assumption built into the device that a valve will start flowing at about 30% of the calibrated pin position, and hence pin positions below this don't call for any heat.

                    Sure, if the valve starts flowing at a significantly different pin position it will still eventually adapt and regulate the temperature somewhat, however that doesn't mean that you won't have problems like calling for heat when the valve isn't flowing or overshooting when other zones come online. Which has been my main point in this thread.

                    As for the difference between the two stroke types, that is not something that has ever seemed a problem to me (all my radiators have Valencias), as I suspect the range of movement is usually absolutely tiny.
                    It certainly is in stroke 0 mode - it only lifts the valve about 1mm off the limit stop for "100% open" despite the valve mechanically having 4mm of travel available. Stroke 1 increases that to about 2mm.
                    I only hear the HR92 motors going continuously (more than a second or so) at the beginning or end of a session, and when wide open (i.e. at the beginning of a session) any given radiator is piping hot, so there's no flow restriction worth worrying about in the "wide-open" position.
                    For your radiators maybe! Not mine. Not being able to get full heat from my living room radiator in stroke 0 mode was an ongoing issue with my old valve bodies, and one of the major reasons why I changed to the Valencia in the first place, thinking all would be perfect with the valves that the HR92 were designed for. But nope! In stroke 0 mode the same problem was there, but even worse.
                    If the HR92 is able to sit (fully screwed on) where it is just beginning to depress the pin, then it should have more than enough room in both directions in the normal stroke configuration.
                    But it's already pushing the pin down by 2mm just by screwing the HR92 base on... refer to the photo I posted. Unless you screw the internal balancer in, but either way you're still halving the available pin travel, and then by using stroke 0, halving it again.
                    I've had a couple of problems with my Valencias getting stuck closed, so could it be that?
                    What made you think they were stuck, and what did you do about it ? If you mean the room was say a degree below the set point but the radiator remained stubbornly cold for an hour then this is exactly the issue I was having that drew my attention to this whole situation in the first place. The pin position was 74% and heat demand about 42% (notice these still correspond exactly on my graph that was derived on my old valves) but a stone cold radiator and after an hour of being a degree below the set point with the boiler running uselessly I decided to investigate.

                    I didn't go looking for problems, they came looking for me!
                    Last edited by DBMandrake; 25 September 2018, 08:52 PM.

                    Comment

                    • blowlamp
                      Automated Home Sr Member
                      • Apr 2017
                      • 98

                      #25
                      If you say the introduction of a spacer has no effect because the HR92 just re-adapts back, then I wonder if the soft rubber seal is the main problem with this setup.

                      If you need to open a valve by 30% of its total travel just to be sure that it's open at all, then something isn't quite right.


                      My I-Temp/Tower combo adjusts in 5% increments and I'm sure there is flow at a pin position of 10%.

                      The I-Temp measures pin position by index impulses off a drive gear and knows the approximate count for a full stroke.
                      Critical dimensions of my valve bodies must have been significantly reducing the stroke length/count causing I-Temp to error out, but introducing the spacer brought the stroke length/count back within tolerance.

                      I-Temp uses the fairly crude (but effective) means of finding a 'valve closed' position by detecting when index pulses slow down or stop.



                      Martin.

                      Comment

                      • rotor
                        Automated Home Guru
                        • Aug 2015
                        • 124

                        #26
                        Originally posted by DBMandrake View Post
                        But how could it learn that ? How would it actually know at what pin position the valve starts flowing when the only feedback it has at all is the flimsiest of indirect evidence of a change in temperature in the room ? The answer is, it simply can't know.
                        I have no knowledge of how HR92s work, but from a purely common sense point of view, how could you design a system that "learns" without any feedback? "Assuming" how a particular radiator valve works --of which there are bound to be hundreds of different designs-- would be pointless. Here's my quick back of an envelope attempt at designing a self-learning HR92:

                        - Set the pin at 50% and request heat
                        - Wait 5 minutes
                        - Did the temperature increase? By how much?
                        - Change the pin position (close it "a bit" if the temperature increased too fast, open it "a bit" if it either decreased, didn't increase, or increased too slowly)
                        - Make note of the rate of temperature increase relative to the pin position. Use this information in future decisions
                        - Continue adjusting the pin position until I understand what pin positions create specific temperature changes; e.g. the two main ones I'm interested in are: a) maintaining room temperature, b) increasing room temperature by 1 degree over a 15 minute period. Notice that these settings are specific to each room (is it a big room or a small one, are there two radiators or just one, are the radiators super efficient or not, do the radiators have a massive lag or not, etc.), and the type and behaviour of the radiator valve is just one more factor that the HR92 has to learn.
                        - The end

                        I know the above doesn't help troubleshoot what is wrong with your setup, but given how flaky Evohome is, I would be tempted to just factory reset everything and start again. The above description should be able to easily achieve the result of getting your radiators to warm up.

                        Comment

                        • DBMandrake
                          Automated Home Legend
                          • Sep 2014
                          • 2361

                          #27
                          Originally posted by rotor View Post
                          I have no knowledge of how HR92s work, but from a purely common sense point of view, how could you design a system that "learns" without any feedback? "Assuming" how a particular radiator valve works --of which there are bound to be hundreds of different designs-- would be pointless. Here's my quick back of an envelope attempt at designing a self-learning HR92:

                          - Set the pin at 50% and request heat
                          - Wait 5 minutes
                          - Did the temperature increase? By how much?
                          - Change the pin position (close it "a bit" if the temperature increased too fast, open it "a bit" if it either decreased, didn't increase, or increased too slowly)
                          - Make note of the rate of temperature increase relative to the pin position. Use this information in future decisions
                          I appreciate the sentiment of what you're saying, and it makes perfect sense to us humans, but trying to implement such a complex and indirect system of inference in a simple device like this using only a single feedback parameter (measured room temperature) just wouldn't work.

                          Some of the hurdles I can think of:

                          1) Whenever the HR92 thinks the room should be hotter, it changes both the valve position and heat demand to the boiler at the same time. How does it know which one of the changes was responsible for an increase in room temperature ? From about 30 to 70% pin position (on a properly calibrated system) both are responsible, however only if this zone is the zone demanding the most heat. If there is another zone that is demanding a lot more heat, only the valve position is affecting the temperature and the change in heat demand is more or less ignored, since the system heat demand to the boiler is simply Max(Zone1,Zone2,Zone3....) etc... From about 70% up it is mainly changes in heat demand that are responsible as most valves are already giving maximum flow by that point, (notice the increase in steepness in the heat demand curve above 70%) however if there is another zone calling for 100% heat at the same time, the 70-100% range is effectively only deadband.

                          2) During the sampling period between making a change and waiting to see what the result is, there can be a lot of outside influences (noise) that can confound making any sense of the result, including changes in heat demand from other zones which will affect the boiler duty cycle, doors being opened and closed, people entering and leaving the room, cookers being turned on, showers being turned on, windows being opened or closed etc. In a busy house there are a lot of confounding variables that make it difficult enough to keep the temperature steady, let alone probe to see where the opening point of the radiator valve might be.

                          3) Radiators heat up quickly and cool down very slowly. If you open it to 50% then wait a few minutes to see what happens (remember it only samples the room temperature roughly every 4 minutes) and you've opened it too much, closing the valve down again will only result in a very slow decline in temperature or rate of temperature rise even. So you'd need to do it the other way around - open it a very small amount, wait, open it slightly more, wait, until finally there is a rise in temperature. This could take a very long time, during which time the house owner is cold and annoyed that they turned their heating on 45 minutes ago and the radiator is still cold!

                          - Continue adjusting the pin position until I understand what pin positions create specific temperature changes; e.g. the two main ones I'm interested in are: a) maintaining room temperature, b) increasing room temperature by 1 degree over a 15 minute period. Notice that these settings are specific to each room (is it a big room or a small one, are there two radiators or just one, are the radiators super efficient or not, do the radiators have a massive lag or not, etc.), and the type and behaviour of the radiator valve is just one more factor that the HR92 has to learn.
                          - The end
                          A lot of the learning process that you describe is actually implemented, so I think you may be misunderstanding my complaint.

                          1) The warm up rate of the room to hit a target at a certain time is learnt over time - this is optimal start, and this learning process is handled by the controller. It uses the learnt thermal response time of the radiator/room and the difference between current temperature and set point to decide how early to change the set point.

                          2) Thermal lag of the radiators/room in terms of overshoot tendency is learnt and adapted to - this is done by the individual HR92's by heuristically self tuning the differential part of the PID controller tuning. So if you make a step change in the set point from say 15C to 20C and the room temperature is 20C, and it goes flying right past 20C because it's rising quickly and still putting out a lot of heat at 20C it will recognise this overshoot, adjust the differential parameter and next time it's in the same situation it will start closing the valve position down well before it reaches the set point in rooms that heat quickly, "coasting" to reach the target. It does a pretty good job of this in most situations.

                          This can happen in reverse too where it undershoots the target, leveling out 1-2C below the set point if it has previously compensated for overshoot. I notice this particularly with a radiator that often has a towel on it which increases the thermal lag to the room considerably - initially that will cause overshoot because it slows the heat output into the room so that its still putting out heat long after the radiator closes, however after removing the towel it then undershoots until it re-learns.

                          3) Offset error is learnt and adapted to automatically as well. This is also done by the individual HR92's by using the integral parameter. For example say it's a warm day so it only takes a valve pin position of 45% to maintain a steady 20C in the room. It learns and adapts to that and will keep the room precisely at 20C. The following day is much colder, now it would require a valve pin position of 65% to put out more heat to maintain the same 20C. When it initially warms up the room it may undershoot slightly however over time (30 minutes to a few hours) it will gradually adjust and hit the target spot on.

                          4) The HR92 can adapt to differences in the valve pin length - to a certain degree. There is about 3.3mm of usable pin travel from the HR92 base, and the calibration process basically winds the pin down until a set force is reached, that is considered to be closed. It then winds it out a set number of turns to reach 100%. In Stoke 0 mode this is typically about 1 turn less than the maximum movement available, in Stroke 1 mode it always winds right out until it hits the outer limit stop in the base.

                          The pin range is then calibrated 0-100% using these two limits. If at any time during operation it reaches one of these limits before it thinks it has, it recalibrates and rescales the range on the fly. So say it is trying to open to 100% and it gets to what it thinks is 90% and then hits the limit stop. It immediately recalibrates this point as 100% and scales the rest of the range proportionally. You can see this happening if you're in the pin position mode when it hits the limit stop. I've found it takes 2-3 full excursions from closed to open to fully "settle" the calibration and stop making small changes to it.

                          Because of this calibration process if the pin is slightly shorter (emulated by adding a shim as discussed earlier) it adapts to this because during the calibration process it pushes the pin down until a certain force is reached or the limit stop is hit. Normally the bottom limit stop is never hit, the force limit is reached first. With the shim it would have to wind down further which means that 0% is slightly further down the range of travel the base allows.

                          That means 100% is further away from 0% hence the valve can open slightly more with the shim. But the amount of pin travel from the closed position to where the valve starts to flow - which is dependent on the compressibility of the washer, doesn't change.

                          Also the relationship between calibrated pin position and heat demand seems to be fixed. It starts calling for heat at about 30% - end of.

                          I'm not saying it couldn't be done better than it is now - one improvement might be for it to have a sensor to actually measure the flow temperature of the pipe that it's sitting on top of to have a better idea of when it starts to flow - using a similar algorithm to the one you describe. However I don't think this would work by trying to sense air temperature in the room, especially with a remote sensor. With a sensor for the pipe temperature, yes.

                          The problem with that idea is that it then makes a huge difference whether the HR92 is on the flow or return side of the radiator. On the flow side it will very quickly detect the pipe is getting hot and get an accurate idea of when it started to flow - on the return side there will be a huge delay due to the cold radiator continuing to pump out cold water for a long time! Another possibility would be an IR sensor aimed at the radiator. But since you can orientate the HR92 in different orientations, and some radiators have side covers that insulate the heat quite well that could also be problematic, and putting it on the return side of the radiator (which is best for air temperature sensing) would introduce the same response delay as directly measuring the pipe temperature.

                          I don't think this is an easy problem to solve, in short, other than having a more versatile Stroke mode setting that allows finer calibration than just two different modes.
                          Last edited by DBMandrake; 27 September 2018, 05:05 PM.

                          Comment

                          • DBMandrake
                            Automated Home Legend
                            • Sep 2014
                            • 2361

                            #28
                            Originally posted by DBMandrake View Post
                            A lot of the learning process that you describe is actually implemented, so I think you may be misunderstanding my complaint.

                            1) The warm up rate of the room to hit a target at a certain time is learnt over time - this is optimal start, and this learning process is handled by the controller. It uses the learnt thermal response time of the radiator/room and the difference between current temperature and set point to decide how early to change the set point.

                            2) Thermal lag of the radiators/room in terms of overshoot tendency is learnt and adapted to - this is done by the individual HR92's by heuristically self tuning the differential part of the PID controller tuning. So if you make a step change in the set point from say 15C to 20C and the room temperature is 20C, and it goes flying right past 20C because it's rising quickly and still putting out a lot of heat at 20C it will recognise this overshoot, adjust the differential parameter and next time it's in the same situation it will start closing the valve position down well before it reaches the set point in rooms that heat quickly, "coasting" to reach the target. It does a pretty good job of this in most situations.

                            This can happen in reverse too where it undershoots the target, leveling out 1-2C below the set point if it has previously compensated for overshoot. I notice this particularly with a radiator that often has a towel on it which increases the thermal lag to the room considerably - initially that will cause overshoot because it slows the heat output into the room so that its still putting out heat long after the radiator closes, however after removing the towel it then undershoots until it re-learns.

                            3) Offset error is learnt and adapted to automatically as well. This is also done by the individual HR92's by using the integral parameter. For example say it's a warm day so it only takes a valve pin position of 45% to maintain a steady 20C in the room. It learns and adapts to that and will keep the room precisely at 20C. The following day is much colder, now it would require a valve pin position of 65% to put out more heat to maintain the same 20C. When it initially warms up the room it may undershoot slightly however over time (30 minutes to a few hours) it will gradually adjust and hit the target spot on.
                            Saw a perfect example of this learning process when I checked my graphs tonight.

                            Earlier in the week evening temperatures were quite low around 5-8C and the system had adapted perfectly to this with the evening living room warmup hitting it's target temperature bang on without any undershoot or overshoot, then yesterday it was suddenly unusually warm in the evening - 16 degrees. This caused a minor overshot as highlighted on the left:



                            The overshoot was only half a degree, and considering the outside conditions had changed from 5-8C to 16C that's relatively minor - with my old sticking valve bodies it would have overshot by 1-1.5C in similar changeable conditions.

                            Last night it would have quickly detected the overshoot and learnt from that. Had the temperature tonight been similarly warm it would have hit the target perfectly without overshooting.

                            However tonight was colder again - about 12C, and you can see on the right hand side that due to learning from yesterdays warm conditions it has actually undershot the target and flattened out about half a degree below the set point. Interestingly at the time I took the screenshot the boiler was completely off and the 15 minute pump overrun had stopped as well. So despite being slightly under the set point it actually wasn't calling for any heat.

                            However over time it will adapt again to the colder temperatures and being slightly under the target - probably by the time we go to bed tonight, if not by tomorrow. In fact while I've been writing this I've just noticed the radiator starting to warm up a bit...
                            Last edited by DBMandrake; 27 September 2018, 07:34 PM.

                            Comment

                            • dty
                              Automated Home Ninja
                              • Aug 2016
                              • 489

                              #29
                              What they need to do is design a combined HR92 with valve body. Then they could include a flow sensor, and even make the whole system self-balancing.

                              Comment

                              • DanD
                                Automated Home Ninja
                                • Feb 2016
                                • 250

                                #30
                                I know this is an old thread, but I thought I'd add my recent positive experience with my Valencia valves after re-reading this thread. I replaced about 5 of valves about a year ago to help fix some problems I was having with valve banging and humming sounds from open valves when the majority of the valves were closed. This fixed most of the problems except for one radiator, in a bathroom. This radiator is often the only one calling for heat as it has a higher setpoint and it continued to produce an occasional humming noise for a few minutes which I believe coincided with the valve attempting to close. I decided to try adjusting the valencia 'balancing' valve insert which was set to near the maximum open setting. By closing the adjuster by only about half a turn it has cured the humming noise and my assumption is that this has helped the valve to close more firmly. I didn't need to mess with the stroke setting on the HR92 which remains set to the default, but this was next on my list, if the adjuster didn't fix the problem.

                                PS when I installed the valencia valves, I decided to use the inserts to balance each radiator and I opened up each of the lockshield valves fully.

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