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Thread: Evohome firmware 02.00.19.31 Beta Trial - Exclusive for Automated Home Members

  1. #621
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    So what is the point of having 0.5 increments, if its not going to work then it should 1.0 increments.
    I would think that getting the 0.5 to work is not a big problem. When I wrote software for Southampton University I would have been ridiculed for such a bug.

  2. #622
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    Quote Originally Posted by philchillbill View Post
    It's a quirk. Bumping the setpoint by 0.5 deg is useless as the controller just magically reports a current temp rounded up to the next half degree after you make the setpoint change. Magnificent UI design by Honeywell.
    What actually happens is the raw measured temperature is biased up to half a degree towards the setpoint and the result is then rounded (up or down) to the nearest 0.5C for final display.

    So for example if the set point is 20C and the true measured temperature is 20.1C, the measured temperature is biased down to 20C (biased towards the set point up to a maximum of 0.5C) and then rounded to the nearest 0.5C - so reports 20C.

    If you then change the set point to 20.5C it will now bias the measured temperature up to a maximum of 0.5C above the true temperature. True temperature is 20.1C and set point is 20.5C, this is then rounded and you get 20.5C.

    If you turned the set point up to 22C while the measured temperature was 20.1C it would bias it to 20.6C then round it up to 21C...

    This "fake temperature display" is independently simulated by all devices - the over the air protocol (and the web API) always reports the true temperature to two decimal places without any rounding or biasing, and the individual devices like DTS92 and HR92 apply this algorithm themselves before displaying the temperature on their screens.

    So adjusting the set point half a degree is not "useless", as it does indeed increase or decrease the ultimate room temperature by half a degree (it will take a while though) however I agree that the measured temperature display on the Evohome system is misleading in the way that it rounds the temperature towards the set point to disguise fluctuations around the set point. And one side effect of this is that the display temperature sometimes shifts half a degree as soon as you adjust the set point, and before the room temperature actually changes.

    I wish it didn't, unfortunately it is baked into the firmware in all the non-firmware upgradeable devices like HR92's (and others like DTS92 that pre-date Evohome) so they couldn't remove it from the controller and Phone app without introducing discrepancies with the readings on other devices...
    Last edited by DBMandrake; 11th November 2020 at 03:52 PM.

  3. #623
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    Quote Originally Posted by clarkie View Post
    So what is the point of having 0.5 increments, if its not going to work then it should 1.0 increments.
    I would think that getting the 0.5 to work is not a big problem. When I wrote software for Southampton University I would have been ridiculed for such a bug.
    The room temperature will actually change if you make a 0.5C adjustment, however with small adjustments it make take a while. (15-30 minutes)

    The immediate change in displayed temperature is an artefact of how the system biases the displayed temperature in the direction of the setpoint as in my previous post. It's just the way the system is designed and I wouldn't get too hung up on the absolute accuracy of the displayed temperature. Just consider the displayed temperature approximate.

    The system does use the true two decimal place measured temperature when it comes to actually controlling the output of the radiator though, so it will try to very accurately regulate the temperature, and in some rooms it can achieve as good as +/- 0.2C or so if you're using a remote sensor.

  4. #624
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    Quote Originally Posted by DBMandrake View Post
    The room temperature will actually change if you make a 0.5C adjustment, however with small adjustments it make take a while. (15-30 minutes)

    The immediate change in displayed temperature is an artefact of how the system biases the displayed temperature in the direction of the setpoint as in my previous post. It's just the way the system is designed and I wouldn't get too hung up on the absolute accuracy of the displayed temperature. Just consider the displayed temperature approximate.

    The system does use the true two decimal place measured temperature when it comes to actually controlling the output of the radiator though, so it will try to very accurately regulate the temperature, and in some rooms it can achieve as good as +/- 0.2C or so if you're using a remote sensor.
    So you're trying to display the same reading on the display as is displayed on radiator valves.

    I have remote temperature devices in all my rooms not really bothered with what the radiators valves are saying.

    So for a test I turned the heating up by 1.0C and within a short while the radiator started to heat up.
    Turning up 0.5C had no effect unless I waited approx 30 minutes.

  5. #625
    Automated Home Sr Member philchillbill's Avatar
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    Quote Originally Posted by DBMandrake View Post
    What actually happens is the raw measured temperature is biased up to half a degree towards the setpoint and the result is then rounded (up or down) to the nearest 0.5C for final display.

    So for example if the set point is 20C and the true measured temperature is 20.1C, the measured temperature is biased down to 20C (biased towards the set point up to a maximum of 0.5C) and then rounded to the nearest 0.5C - so reports 20C.

    If you then change the set point to 20.5C it will now bias the measured temperature up to a maximum of 0.5C above the true temperature. True temperature is 20.1C and set point is 20.5C, this is then rounded and you get 20.5C.

    If you turned the set point up to 22C while the measured temperature was 20.1C it would bias it to 20.6C then round it up to 21C...

    This "fake temperature display" is independently simulated by all devices - the over the air protocol (and the web API) always reports the true temperature to two decimal places without any rounding or biasing, and the individual devices like DTS92 and HR92 apply this algorithm themselves before displaying the temperature on their screens.

    So adjusting the set point half a degree is not "useless", as it does indeed increase or decrease the ultimate room temperature by half a degree (it will take a while though) however I agree that the measured temperature display on the Evohome system is misleading in the way that it rounds the temperature towards the set point to disguise fluctuations around the set point. And one side effect of this is that the display temperature sometimes shifts half a degree as soon as you adjust the set point, and before the room temperature actually changes.

    I wish it didn't, unfortunately it is baked into the firmware in all the non-firmware upgradeable devices like HR92's (and others like DTS92 that pre-date Evohome) so they couldn't remove it from the controller and Phone app without introducing discrepancies with the readings on other devices...
    The danger in showing a faked value for a 'current' temperature that the system will take 30 mins to reach is that a different house member may see the faked temperature and adjust back downwards again, thinking that it's already warmer than it actually is. You can get accustomed to quirky behaviour over time and work around it, but that does not mean it's good UI design.

  6. #626
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    Quote Originally Posted by philchillbill View Post
    The danger in showing a faked value for a 'current' temperature that the system will take 30 mins to reach is that a different house member may see the faked temperature and adjust back downwards again, thinking that it's already warmer than it actually is. You can get accustomed to quirky behaviour over time and work around it, but that does not mean it's good UI design.
    Oh I totally agree. I think it's a mistake but it's one they're stuck with for as long as they support all legacy Ramses compatible devices since those have the silly bias algorithm built into their non-upgradeable firmware.

    My reply was mainly to correct the notion that making a half degree adjustment doesn't do anything - it does and I do it all the time. And the system does try its hardest to keep the true temperature very close to the set point, despite its slightly "faked" temperature display. A couple of our zones once up to temperature manage to stay within +/- 0.1C if not disturbed (doors opened/closed) as measured using the web API or an independent thermometer, which is extremely good and 20x better than what a mechanical TRV can achieve.

  7. #627
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    Also if you can read the radio signals, it gives you two decimal places temperature readings, which are then further subjected to the adjustments mentioned above.

  8. #628
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    Another test today bedroom radiator stone cold. Display indicates 17.0C domoticz indicates 17.3C.
    Turn the heat up to 17.5C a few minutes later display indicated 17.5C system summary bedroom requesting 0% heat.
    Waited 30 minutes radiator stone cold 0% heat request.
    Waited 60 minutes radiator stone cold 0% heat request.

    So can you tell me what temperature difference is required to heat the radiator.
    Is the temperature difference compared against the setpoint and the actual temperature or the "fake" temperature?

  9. #629
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    What were the domoticz measured room temps at the 30m and 60m points? Was it cooling or staying constant?

  10. #630
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    Didn't change stayed at 17.3C.
    Just a thought could you not display the fake temperature all the time.

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