Evohome HR92 valves reporting wrong temperature

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  • mbf82
    Automated Home Jr Member
    • Jan 2016
    • 10

    Evohome HR92 valves reporting wrong temperature

    Hi all,

    I just got a evohome installed (by some professional as I needed some boiler work, installing some valves on radiators that didn't have them, etc...).
    My setup includes a condensing combi boiler for heating and hot water, an evohome controller + relay, 6 radiators with 6 HR92 valves, 3 radiators with normal valves (two will be
    replaced by heated towel rails, one will be removed when I redo the kitchen in a few weeks). The radiators and their valves are all far from furniture and not covered by curtains.

    I have a few problems/questions with the temperature controls and I haven't found the answers I need in the old posts.

    The temperature detected by the valves when the radiator is on or still warm is several degrees (4 or 5) higher than the one in the middle of the room. On the other hand, the temperature is correct then the radiator is cold, so I cannot just change the temperature offset.
    In the last two days I had to keep setting the room temperature to 24C until the centre of the room is warm (about 20C) and then decrease the set temperature to 21 or 22C so it will stay at about 20C.

    Is this normal? I expected some difference, but not this much as it basically makes the system useless and impossible to control.
    Could some DTS92 thermostats help? If I understand correctly, I can use those to pick up the temperature and use the HR92 valves only as actuators.
    Is it possible to fix the DTS92 to the wall instead of just using the desk stand?

    My other question seems to be about a potential bug in the software. Let's say that the valve (and controller and app) think that a room is a 20C, but it's actually colder, so I set the temperature manually (with the app or controller) to 22C. Immediately after doing that, the app/controller will report an increase of 0.5C in the detected room temperature, even before actually turning the heating on. This seems to happen about 50% of times. Does this happen only to me?
  • killa47
    Automated Home Guru
    • Jan 2016
    • 123

    #2
    HI mbf82,

    I've had the system since November and I too have noticed the temp instantly reports a 0.5C increase. Must be a flaw in the App as I have not spotted this on the controller. I tend to be now using the App miore than the controller but would also appreciate some insight as to when users will receive the new firmware (I accept that beta trialling has to complete first).

    Comment

    • DBMandrake
      Automated Home Legend
      • Sep 2014
      • 2361

      #3
      Originally posted by mbf82 View Post
      Hi all,

      I just got a evohome installed (by some professional as I needed some boiler work, installing some valves on radiators that didn't have them, etc...).
      My setup includes a condensing combi boiler for heating and hot water, an evohome controller + relay, 6 radiators with 6 HR92 valves, 3 radiators with normal valves (two will be
      replaced by heated towel rails, one will be removed when I redo the kitchen in a few weeks). The radiators and their valves are all far from furniture and not covered by curtains.

      I have a few problems/questions with the temperature controls and I haven't found the answers I need in the old posts.

      The temperature detected by the valves when the radiator is on or still warm is several degrees (4 or 5) higher than the one in the middle of the room. On the other hand, the temperature is correct then the radiator is cold, so I cannot just change the temperature offset.
      In the last two days I had to keep setting the room temperature to 24C until the centre of the room is warm (about 20C) and then decrease the set temperature to 21 or 22C so it will stay at about 20C.

      Is this normal? I expected some difference, but not this much as it basically makes the system useless and impossible to control.
      Could some DTS92 thermostats help? If I understand correctly, I can use those to pick up the temperature and use the HR92 valves only as actuators.
      Is it possible to fix the DTS92 to the wall instead of just using the desk stand?
      This isn't a bug/fault in the HR92, but a fundamental limitation of measuring the temperature of a room right beside a hot radiator. It doesn't matter whether you have a conventional wax pellet mechanical TRV or an electronic sensor like the HR92. On a conventional manual TRV you just never knew how inaccurate this measurement location was because it has no readout. Ever wonder why conventional TRV's are labelled with 1 through 5 instead of a temperature in Celsius ? Now you know.

      As the room heats up from cold the middle or far side of the room could initially be as much as 3-4 degrees or so below the temperature measured by the HR92 as you have noted. About 1 degree of this error is due to the the close proximity of the HR92 to the side of the radiator - which can be compensated for by setting the calibration to -1 degree. I have all my HR92's set to -1 after comparison with a more distant room thermometer after the room (with closed doors/windows) has reached final equilibrium. Of course this means that when the radiator is cold the temperature reading will be about 1 degree below the "true" reading, but there is not much you can do about that unless you use a remote sensor that is not right beside the radiator.

      The rest of the initial error that you describe (up to about 2-3 degrees I have seen) is not actually an "error" but a reflection of the fact that the side of your room near to the radiator is genuinely 2 or 3 degrees hotter than further parts in the room when the room is initially heating up. I think people generally assume that a room only has one temperature but this is not the case - any time the room is heating up in response to a radiator on one side there will be a temperature gradient across the room that causes heat to gradually flow from the hot side of the room to the colder side. There is a "thermal lag" on the far side of the room, and depending on where you measure in the room you will get quite a different result.

      The HR92 will maintain a steady set temperature in the vicinity of the radiator during this time and will not report any change in temperature however heat will flow from the hotter side of the room to the cooler side of the room and the rest of the room will eventually "catch up" with the temperature of radiator side of the room reaching an equilibrium - so you would see this temperature gradually climb on a thermometer located on the other side of the room, but it can take a long time (an hour or more) depending on the construction of the room. We have solid brick with plaster for all interior walls downstairs and I definitely notice this effect when I have checked with another thermometer.

      As this is not an error in the reading but simply a reflection of the fact that you're measuring the temperature of the hot side of a room that initially started off cold and therefore has a heat gradient across the room, you can't try to correct for this with the calibration setting. Another thing to keep in mind is that only a closed, reasonably well insulated room will reach a final equilibrium where the entire room is about the same temperature. If you have a room where the radiator is at one end and an open door into a colder or drafty hallway is left open there will always be a heat gradient across the room where the radiator side of the room is warmer than the door side of the room, probably by 2-3 degrres - no heating control system can do anything about this it's a fundamental fact of physics and the way heat flows.

      If you would like the "middle" of the room to heat up quicker to your target temperature than in this scenario you could use a remote stat like a DTS92 either wall or table mounted at least 1.5 metres from the radiators. Now it will try to optimise the temperature where the stat is located instead of in the vicinity of the radiator. However assuming you put the stat on a wall near the "middle" of the room, by doing so the temperature of the room near the radiator will now overshoot the set target temporarily as the room heats up while heat is still flowing from the hot to the cold side of the room. When eventual equilibrium is reached (with closed doors/windows) the temperature of the radiator side of the room will drop again and the room temperature will be relatively even throughout the room again.

      So it depends whether you prefer the cold side of the room to warm up quicker or whether you don't want the hot side of the room to overshoot. Personally I find overshoot more uncomfortable than just taking a bit longer to warm up.

      In something like a living room an acceptable compromise might be a wall stat near the seating position. A remotely located stat is always going to be more accurate because it is not influenced by the direct heat from the radiator and it can be placed in the part of the room that you're interested in, such as the seating position. Just keep in mind that the whole room will still not have one temperature when heating up, the side near the radiators will be warmer than the other side of the room until it reaches thermal equilibrium. (Actually there will always be a small gradient)
      My other question seems to be about a potential bug in the software. Let's say that the valve (and controller and app) think that a room is a 20C, but it's actually colder, so I set the temperature manually (with the app or controller) to 22C. Immediately after doing that, the app/controller will report an increase of 0.5C in the detected room temperature, even before actually turning the heating on. This seems to happen about 50% of times. Does this happen only to me?
      No, it's a known behaviour of the evohome system - apparently it rounds the displayed temperature towards the set point by up to a maximum of 0.5 degrees. Why they chose to do this, nobody knows but it has been confirmed to behave this way. It doesn't affect the functioning of the system but personally I don't like this behaviour.

      It does however mean that if you are trying to do a temperature comparison between the evohome and another thermostat, the comparison is only valid if the room is at the set point - if the set point is a long way above or below the current temperature there will be a bias of up to half a degree in the direction of the set point.

      Another thing to consider when comparing readings to another thermostat is that different thermostats have different response times to changes - the evohome sensors are quite quick responding compared to many other typical stand mounted room thermostats, such as the weather station one I use. (Which includes outdoor temperature, humidity etc) So if you are trying to do a comparison between the two not only should they be near each other you should let the room temperature stabilise for some time so that differences in the response time of the thermostats doesn't introduce another error in your comparison.
      Last edited by DBMandrake; 15 January 2016, 01:55 PM.

      Comment

      • DBMandrake
        Automated Home Legend
        • Sep 2014
        • 2361

        #4
        Originally posted by killa47 View Post
        HI mbf82,

        I've had the system since November and I too have noticed the temp instantly reports a 0.5C increase. Must be a flaw in the App as I have not spotted this on the controller. I tend to be now using the App miore than the controller but would also appreciate some insight as to when users will receive the new firmware (I accept that beta trialling has to complete first).
        This behaviour is still there on the new firmware. Unfortunately I suspect this is considered to be a "feature not a bug" by honeywell.

        Comment

        • mbf82
          Automated Home Jr Member
          • Jan 2016
          • 10

          #5
          Originally posted by DBMandrake View Post
          This isn't a bug/fault in the HR92, but a fundamental limitation of measuring the temperature of a room right beside a hot radiator. It doesn't matter whether you have a conventional wax pellet mechanical TRV or an electronic sensor like the HR92. On a conventional manual TRV you just never knew how inaccurate this measurement location was because it has no readout. Ever wonder why conventional TRV's are labelled with 1 through 5 instead of a temperature in Celsius ? Now you know.
          I understand that one side is warmer than the other. I just expected the gradient to be less “sudden” as the thermometer was less than one metre from the living room radiator and about 80cm from the small bedroom one.

          I think I will get some DTS92s for the living room and bedrooms and try to find a good position to fix them on the wall.
          I've looked at some manuals I found on google, but I haven't found any documentation on how to associate a DTS92 to an existing valve and controller. Does anybody have any pointer?

          Originally posted by DBMandrake View Post
          No, it's a known behaviour of the evohome system - apparently it rounds the displayed temperature towards the set point by up to a maximum of 0.5 degrees. Why they chose to do this, nobody knows but it has been confirmed to behave this way. It doesn't affect the functioning of the system but personally I don't like this behaviour.
          I see. It vaguely makes sense, but seems like an odd and confusing behaviour.

          Comment

          • DBMandrake
            Automated Home Legend
            • Sep 2014
            • 2361

            #6
            Originally posted by mbf82 View Post
            I understand that one side is warmer than the other. I just expected the gradient to be less “sudden” as the thermometer was less than one metre from the living room radiator and about 80cm from the small bedroom one.
            Ok I didn't realise you were measuring that close.

            In that case I would suspect that the thermometer you're measuring with is quite slow to react, thus is lagging behind the real temperature by a significant amount of time. As I mentioned, I've found the temperature sensors in both the HR92 and the Evotouch itself to be very quick responding and they respond far quicker than my table top thermometer, so if the room is warming up quickly the table top thermometer lags behind by quite a lot until the room temperature is steady.

            Try positioning your thermometer propped up right beside the HR92 and try it again to see if there is a discrepancy or not. If there is still a bit discrepancy when the room is warming up it's likely that it's just a slow thermometer.
            I think I will get some DTS92s for the living room and bedrooms and try to find a good position to fix them on the wall.
            I've looked at some manuals I found on google, but I haven't found any documentation on how to associate a DTS92 to an existing valve and controller. Does anybody have any pointer?
            You don't associate it to the valve, you associate it to a zone on the controller. It's pretty easy to add to an existing zone - make sure the DTS92 is cleared of any bindings - it shouldn't have any when it's new but you never know.

            Instructions are here:



            In the evotouch you would hold down on Settings for 5 seconds to go into the Installer menu, choose to edit the existing zone and there is an option that says sensor, which will currently say radiator. Press this then choose remote sensor, it will ask you to bind the remote sensor - press the buttons on the DTS92 described in the manual above to bind and that's it! To go back to the HR92 as a sensor follow the same procedure but press the binding button on the HR92 rather than the DTS92.

            BTW the Evotouch itself has a built in temperature sensor so for testing purposes you could try using the evotouch in place of where you are thinking of putting a DTS92 to get an idea of what effect it might have on the temperature control. This assumes your evotouch isn't already using it's sensor for the zone its in. The cavet if you do this is it needs to stay in the same location and it does of course need to remain powered.

            Comment

            • mbf82
              Automated Home Jr Member
              • Jan 2016
              • 10

              #7
              Originally posted by DBMandrake View Post
              Ok I didn't realise you were measuring that close.

              In that case I would suspect that the thermometer you're measuring with is quite slow to react, thus is lagging behind the real temperature by a significant amount of time. As I mentioned, I've found the temperature sensors in both the HR92 and the Evotouch itself to be very quick responding and they respond far quicker than my table top thermometer, so if the room is warming up quickly the table top thermometer lags behind by quite a lot until the room temperature is steady.

              Try positioning your thermometer propped up right beside the HR92 and try it again to see if there is a discrepancy or not. If there is still a bit discrepancy when the room is warming up it's likely that it's just a slow thermometer.
              It's quite fast. The sensor seems to update ones every minute. If the difference of temperature is big it can take a couple of updates to stabilise.

              You don't associate it to the valve, you associate it to a zone on the controller. It's pretty easy to add to an existing zone - make sure the DTS92 is cleared of any bindings - it shouldn't have any when it's new but you never know.
              Oh, that's interesting. Thanks!

              BTW the Evotouch itself has a built in temperature sensor so for testing purposes you could try using the evotouch in place of where you are thinking of putting a DTS92 to get an idea of what effect it might have on the temperature control. This assumes your evotouch isn't already using it's sensor for the zone its in. The cavet if you do this is it needs to stay in the same location and it does of course need to remain powered.
              Oh, that's cool as I'm considering wall mounting the controller in the living room.
              How do I associate the controller itself to a zone?

              Comment

              • DBMandrake
                Automated Home Legend
                • Sep 2014
                • 2361

                #8
                Originally posted by mbf82 View Post
                It's quite fast. The sensor seems to update ones every minute. If the difference of temperature is big it can take a couple of updates to stabilise.
                By fast I don't mean how often it polls the sensor to update the displayed temperature, I mean how quickly the sensor reacts to a large change in temperature.

                So for example if you moved a thermometer from a 15 degree room to a 20 degree room, even if the reading is polled and changes slightly every minute, it may still take a long time until the reading approaches 20 degrees.

                This is mainly dependent on the thermal mass of the sensing element and also how well air can flow through the casing. My thermometer reads down to 0.1 degree increments and I think it updates once every minute like yours, but it is still very slow at adapting to changes in room temperature. I would say it would take it half an hour probably more to go from 15 to 20 if I moved it between two rooms maintained at those temperatures.

                Oh, that's cool as I'm considering wall mounting the controller in the living room.
                How do I associate the controller itself to a zone?
                The same way as above - you go into the installer menu, edit the zone you want to change, and then for sensor you choose evotouch instead of remote sensor. In the system settings section you can also adjust the calibration (offset) of the built in sensor in 0.1 degree increments. (Unlike the HR92 where you can only change it in full degree steps)

                Comment

                • mbf82
                  Automated Home Jr Member
                  • Jan 2016
                  • 10

                  #9
                  I understood what was happening.

                  The heating was off all day during some of the coldest days of the year, so the rooms cooled down quite a bit. When the heating turned on the radiators got very hot (and the room a bit warmer but still too cold). Then the radiators turned off because the sensor thought it was much warmer. As the radiators take several hours to cool down, the sensor kept thinking it was quite warm.
                  A few hours later the cycle happened again and the room got closer to the temperature I want and so on.
                  Over the weekend I managed to keep the temperature I want everywhere because the heating was on all day, so the rooms couldn't cool down enough to show this problem (and I set the target temperature to 1C more).

                  In the living room things worked better as I associated the controller as sensor for the zone.

                  After this experiment I decided to get some DTS92s for the various rooms (and not bother with hallways and landing as they don't matter much and they are surrounded by warm rooms).

                  Comment

                  • HenGus
                    Automated Home Legend
                    • May 2014
                    • 1001

                    #10
                    I have used Evohome now for over 18 months and, yes, it is true that from time to time the odd zone can get above target temperature. In my experience, this is because the controller does not - and cannot - regulate the temperature of the CH water coming out of the boiler. In the 'good old days', the timer clicked ON and the hall thermostat demanded heat. Water circulated around the system and TRVs closed as the required temperatures were reached. Zoning allows heat to come on whenever and where ever it is demanded. In some zones, the CH water will be warming up: in some zones the water reaches the radiator at max boiler temperature (or as new as is possible). It is in the latter situation, when most of my zones are effectively 'Off', that I see HR92 over-reads. It doesn't happen as much if the HR92 is just maintaining a zone temperature: in such situations, the usual over temperature is 0.5C. Personally, whilst I love gadgets, I am not sure that spending even more on Evohome is worth it from a comfort or energy saving/cost saving perspective.

                    Comment

                    • DBMandrake
                      Automated Home Legend
                      • Sep 2014
                      • 2361

                      #11
                      Originally posted by mbf82 View Post
                      I understood what was happening.

                      The heating was off all day during some of the coldest days of the year, so the rooms cooled down quite a bit. When the heating turned on the radiators got very hot (and the room a bit warmer but still too cold). Then the radiators turned off because the sensor thought it was much warmer. As the radiators take several hours to cool down, the sensor kept thinking it was quite warm.
                      You must have massive radiators if they take hours to cool down! Typical cooldown time for radiators is in the 15-30 minute range in my experience. If they really do take that long to cool down then any control system measuring the temperature right at the radiators is going to struggle to perform optimally.
                      A few hours later the cycle happened again and the room got closer to the temperature I want and so on.
                      Over the weekend I managed to keep the temperature I want everywhere because the heating was on all day, so the rooms couldn't cool down enough to show this problem (and I set the target temperature to 1C more).

                      In the living room things worked better as I associated the controller as sensor for the zone.

                      After this experiment I decided to get some DTS92s for the various rooms (and not bother with hallways and landing as they don't matter much and they are surrounded by warm rooms).
                      It sounds like your scenario would benefit from a DTS92 mounted away from the radiators out in the room. It seems that you have a lot of thermal mass in your room (do you have solid interior walls like we do ?) and therefore a lot of thermal lag, and thus measuring the temperature at the radiator is not optimal for warm up time.

                      As you note, the HR92 will not allow the small part of the room in the vicinity of the radiator to go (much) over the set temperature, so once that part of the room is warmed up it will close the radiator valve down to maintain that local temperature, even though a further part of the room could still be several degrees below the desired set point due to thermal lag of the room. (And if it overshoots significantly, it will completely close the valve until the temperature drops down a bit again)

                      It should be pointed out that conventional mechanical TRV's have the exact same problem - during the warmup phase of a cold room, once you get within a few degrees of the set temperature the TRV will prematurely close due to it sensing a higher temperature than the rest of the room and not open again until the radiator cools, then once the radiator heats up it will prematurely close again, so the last few degrees of temperature rise of the rest of the room is a lot slower than it should be as the radiator keeps going off and on again.

                      The typical way people get around this shortcoming is they manually turn their (conventional) TRV's up a notch until the room is warm enough then turn them down again...

                      If you use a DTS92 to remote sense the temperature in the room it will not be fooled by the localised heating around the radiator, and it will allow the radiator to stay fully open right up until the room is nearly at temperature, allowing the temperature in the immediate vicinity of the radiator to go "over temperature" temporarily to allow the rest of the room to reach the correct temperature as quickly as possible.

                      When you change the location of the temperature sensor it may take the evotouch a few days to re-learn the thermal characteristics of the room, so you might actually get a bit of temperature overshoot for a few days but it will quickly adapt.

                      I too have been experimenting with using the Evotouch as the temperature sensor, this time in the bedroom - sitting above the head of the bed on the opposite side of the room from the window. I find with the bedroom because the radiator is directly below the window the cold air from a slightly ajar window at night will tend to trigger the radiator to come on when the room is not really below the night time set point of 15 degrees, so it will sometimes come on unnecessarily. Also the same issue of the rest of the room taking a while to come up to temperature that you note in your room.

                      Initial results are very promising - the radiator does not come on prematurely with the cold air from the window and the room gets up to the correct temperature a lot quicker in the morning without any overshoot, and I can feel that the room is maintaining a much more consistent temperature - at least over near the bed where the sensor is. (but that's the point of locating it there...) I always planned to get a DTS92 for the bedroom wall but it was interesting to confirm that the control improved in the way I expected it would. I still want to finish zoning first by getting HR92's for the rest of the radiators which don't yet have them but once I have done that I plan to get DTS92's for the bedroom and living room.

                      A remote temperature sensor is always going to be more accurate, it's only a matter of deciding which rooms really need them and which don't - for example does it really matter if your hallway temperature control is not quite as precise or doesn't warm up quite as quickly as it it could ? Probably not... but for me Living room and Bedroom are the two rooms we spend a lot of time in where you want the temperature to be as well controlled as possible for comfort.

                      Let us know how you get on with your DTS92's.
                      Last edited by DBMandrake; 18 January 2016, 10:50 AM.

                      Comment

                      • DBMandrake
                        Automated Home Legend
                        • Sep 2014
                        • 2361

                        #12
                        Originally posted by HenGus View Post
                        I have used Evohome now for over 18 months and, yes, it is true that from time to time the odd zone can get above target temperature. In my experience, this is because the controller does not - and cannot - regulate the temperature of the CH water coming out of the boiler.
                        That's not actually true - if you use the OpenTherm interface with an OpenTherm compatible boiler it does specifically control the flow temperature of the boiler based on demand. If demand is high (cold rooms warming up and radiator valves fully open) it will run it at the maximum flow temperature that you have configured on the boiler to achieve the quickest warmup time. However when demand is low (zones all up to temperature and just trying to maintain their temperatures) it will reduce the flow temperature to the lowest temperature that will maintain the status quo. This helps a condensing boiler remain in condensing mode and minimises the possibility of temperature overshoots, especially if you have oversized radiators.

                        If like me you use a BDR91 instead of an OpenTherm interface the situation is not quite as rosy - it will try to modulate the flow temperature of the boiler using TPI. By default it uses 10 minute intervals (6 firings per hour) so it will fire the boiler anywhere between 1 minute and 10 minutes every 10 minute period to control the boiler duty cycle. If the boiler only fires for 5 minutes in every 10 minute period, it stands to reason that the total heat output of the boiler will be reduced, and therefore the average flow temperature will drop.

                        The problem is that this whilst better than nothing, is fairly imprecise because variables the controller can't know affect what flow temperature you end up with. If your boiler is set to 75 degrees but runs 2 minutes out of 10 and you only have one radiator open you might achieve a flow temperature of 60 degrees, but if you had 5 radiators open the heat loss of that many radiators might cause you to end up with a flow temperature of 40 degrees for a 2 minute firing...

                        I talk about this problem here: http://www.wordpress-1219309-4387497...me-explanation

                        Basically, if you can use OpenTherm, you should do so, it should give better control and also give savings on a condensing boiler.

                        Another complication of modulating the boiler flow temperature either via OpenTherm or TPI is that if a zone suddenly increases its set point by more than 1.5 degrees it will increase the heat demand to maximum, bringing the boiler fully on, this can lead to a temporary overshoot in other zones because the HR92's were balancing their valve openings against the current flow temperature only to have the flow temperature increase - now they need to throttle themselves down further, and during this adaption there may be a small overshoot.
                        In the 'good old days', the timer clicked ON and the hall thermostat demanded heat. Water circulated around the system and TRVs closed as the required temperatures were reached. Zoning allows heat to come on whenever and where ever it is demanded. In some zones, the CH water will be warming up: in some zones the water reaches the radiator at max boiler temperature (or as new as is possible).
                        This is not really correct - there is only one flow temperature as it comes out of the boiler at any given time. If the system is well balanced the water temperature entering each flowing radiator will be about the same, of course when the water flows through a cold radiator that water cools down as it comes out again so it does take time for the metal of the radiator itself to heat up, but a radiator will heat up much much quicker if turned on after the rest of the system including other flowing radiators is already hot - typically only a couple of minutes.

                        HR92's aren't any different to a conventional TRV as far as water flow is concerned, the main difference (apart from being more accurate, and remote controllable) is that they have the ability to "call for heat" from the evotouch which in turn calls for heat from the boiler, whereas a conventional TRV obviously can't do this.
                        It is in the latter situation, when most of my zones are effectively 'Off', that I see HR92 over-reads. It doesn't happen as much if the HR92 is just maintaining a zone temperature: in such situations, the usual over temperature is 0.5C. Personally, whilst I love gadgets, I am not sure that spending even more on Evohome is worth it from a comfort or energy saving/cost saving perspective.
                        Just because an HR92 measuring the temperature locally reports the temperature has gone half a degree over doesn't necessarily mean that the room as a whole has gone over temperature, especially if there is a lot of thermal mass in the room. You'll probably find that the temperature out in the room is not overshooting, at least that's been my experience.

                        Comment

                        • HenGus
                          Automated Home Legend
                          • May 2014
                          • 1001

                          #13
                          I am not a heating engineer: I can only report what I see on the controller. I appreciate that many here want more than it would appear Evohome can currently offer. My configuration is simple in that the BDRs control two motorised zone valves on a heating system with a 14 year old non-condensing boiler. The controller regulates the temperature in the hall/landing and stairs. Evohome is far from perfect, but my wife and I are very happy with the level of control and comfort that Evohome brings. That said, it is not a system that I would recommend for people focussed solely on saving energy.

                          As I write, I have a small radiator in my study which is set at 18C. The controller is currently showing a temperature of 20.5C. I can't say that I am losing any sleep over it.

                          Comment

                          • DBMandrake
                            Automated Home Legend
                            • Sep 2014
                            • 2361

                            #14
                            Originally posted by HenGus View Post
                            I am not a heating engineer: I can only report what I see on the controller. I appreciate that many here want more than it would appear Evohome can currently offer. My configuration is simple in that the BDRs control two motorised zone valves on a heating system with a 14 year old non-condensing boiler. The controller regulates the temperature in the hall/landing and stairs. Evohome is far from perfect, but my wife and I are very happy with the level of control and comfort that Evohome brings. That said, it is not a system that I would recommend for people focussed solely on saving energy.

                            As I write, I have a small radiator in my study which is set at 18C. The controller is currently showing a temperature of 20.5C. I can't say that I am losing any sleep over it.
                            I can beat you on the boiler front - 22 year old non condensing boiler. No zone valves, just a boiler relay.

                            Regarding your study, what is the temperature of the adjoining room, and is the door left open or closed ?

                            I agree about energy savings as well - unless you have several mostly unused rooms (which we do actually) then you won't save a huge amount off your energy bill via the Evohome, especially in ROI terms, but for me the purchase was always about comfort, control and convenience. The fact that we can turn the heating off when we go out and turn it back on remotely before coming home, and rooms that don't need to be on all day can turn themselves off at the right times probably does save some energy though.

                            And we quibble about small errors in temperature control, overlooking the fact that conventional on/off (non TPI) wall stats and manual TRV's are horrendously inaccurate... somehow when we get a system like the Evohome we expect perfection instead of just a significant improvement.
                            Last edited by DBMandrake; 18 January 2016, 11:56 AM.

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                            • G4RHL
                              Automated Home Legend
                              • Jan 2015
                              • 1580

                              #15
                              Originally posted by HenGus View Post
                              I am not a heating engineer: I can only report what I see on the controller. I appreciate that many here want more than it would appear Evohome can currently offer. My configuration is simple in that the BDRs control two motorised zone valves on a heating system with a 14 year old non-condensing boiler. The controller regulates the temperature in the hall/landing and stairs. Evohome is far from perfect, but my wife and I are very happy with the level of control and comfort that Evohome brings. That said, it is not a system that I would recommend for people focussed solely on saving energy.

                              As I write, I have a small radiator in my study which is set at 18C. The controller is currently showing a temperature of 20.5C. I can't say that I am losing any sleep over it.

                              Like others I did not go the Evohome route to save money specifically but more to have a more balanced heat round the house with full control on a room by room basis. That has been achieved. However, I think there has been a financial saving. I installed Evohome in December 2014. I eventually had it properly bound and configured in early January 2015. During 2014 I used 18,190.47 kWhs of gas. In 2015 I have used 17,150.79. A drop of 1,039.68 or roughly 5.716%. Weather wise the two years were not much different. However, in 2014 I was away toward the end of the year for 6 weeks, returning to install Evohome in the December. The drop in consumption is therefore more than the figures show for had I not been away the units used in 2014 would have been greater than the 18,190.47. 2015 we have only been away for a couple of nights on about 5 occasions.

                              Therefore it points to some saving as a result of using Evohome.

                              All fine but putting this into £s is not so fine. I was with British Gas and changed to Sainsbury’s Energy at the beginning of 2015. I know they are the same company but BG seems to want to undercut itself and Sainsbury's came up the cheapest on comparison sites. Sainsbury’s estimated my combined bill for 2015, based on 2014 consumption at £1140. A saving of £231.37. However, if I apply Sainsbury’s 2015 charging rate to the 2014 consumption my bill would have been £1408.30 which is £268.30 more than they estimated! I have asked them for an explanation!

                              Change time is here again and having checked three comparison sites I am told I will save up to £361 based on 2015 consumption. Do I believe them?!! What is worse they all correctly tell me what contract I am on with Sainsbury’s but the figure they say is the unit price is far lower than Sainsbury’s are charging. The comparison sites tell me my current charge from Sainsbury’s is 8.850p for electricity and 3.130p for gas. The actual charge is 16.76p and 4.13p respectively. I accept my latter figures include the standing charge but the latter would not make such a big difference. This then begs the question as to how good the comparison sites are. But then perhaps all this is something for another forum!

                              As for Evohome I remain pleased with it. It just works! I would like to be able to monitor more what is happening on my computer, presumably that is what the new HG180 will let me do.

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