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Thread: Evohome + HGI80 & Domoticz users - zones calling for heat functionality?

  1. #21
    Automated Home Legend paulockenden's Avatar
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    Thanks Dan.

  2. #22
    Automated Home Legend paulockenden's Avatar
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    This is odd: one of my rads apparently got a 325.1 degrees set point a couple of days ago!

    image.jpg

    Rad isn't actually on though, or showing this rogue setpoint.

    P.

  3. #23
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    Hi Paul,

    That's an odd one, I've not seen that happen before with the setpoint values. The 325.1 is the value that the Evohome system uses for missing data and I've seen it occur with the zone temperature. Is the device one of the standard zone temperature sensors or one of the additional 'All Sensors' ones? I'm guessing that it's probably one of the 'All Sensors' ones which are updated directly from messages sent from the sensor and this might be a bug the code where it's not correctly handling the heating-off state. I'll take a look at the code and see if I can track down what might cause this condition.

    Dan

  4. #24
    Automated Home Legend paulockenden's Avatar
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    You've got it. One of the rads had accidentally be knocked into the off position (easy to do when the 'off' quick-action is set, and so the rad setpoints are all 5 degrees). It only takes a small nudge, and of course once set to off it won't be reset by the next schedule change. It would be better if 'off' required a more positive action.

  5. #25
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    Thanks Paul for spotting this bug. I've updated the code to set the setpoint value to 0 when the HR92 has been set to Off so they should plot OK. The update should make its way to a beta in the next few weeks.

    Dan

  6. #26
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    Should it not graph 5 degrees instead of 0 in OFF mode ?

    Although I have not tested to confirm it, reading the Honeywell documentation suggests that although OFF mode ignores set point changes from the controller, it still maintains a frost protect set point of 5 degrees internally - eg if the room temperature falls below 5 degrees the valve will still open and also wirelessly call for heat from the boiler.

    So in that regard OFF and 5.0 are the same, the only difference being whether remote set point changes will be ignored or not.

    I don't think it's possible to defeat the frost protect minimum set point of 5.0 degrees in any way through the user interface, short of unlatching the HR92 from the valve body.
    Last edited by DBMandrake; 18th June 2016 at 03:28 AM.

  7. #27
    Automated Home Legend paulockenden's Avatar
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    Off at the controller is 5 degrees. But I think off at the HR92 is off. At least, it's different to setting a 5 degree local over-ride.

  8. #28
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    Thanks, I really appreciate the feedback. I hadn't thought through the possible effect of the change. After further testing, I'm relieved to say that the 0s were totally ignored by the HR92, just as you thought and kept on being reset. I'm going to leave these values unchanged and users will have to post-process extracts when graphing. I'm going to take a look at the Domoticz code to see if I can remember where the formatting is applied as I'd like to display these flags as Off rather than the real value in some of the Domoticz screens. I've messed with this formatting in the past, but can't quite track it down at the moment.

  9. #29
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    For reference, the Evohome missing and off temperature values/flags are as follows:

    Missing temperature value: 327.7 (raw 0x7FFF)
    Off setpoint temperature value: 325.1 (raw 0x7EFF)

    You'll only encounter the raw values if you're messing with the messages sent between Evohome devices, any extracts from Domoticz via JSON etc will report the converted decimal values which are just the raw values divided by 100 with no rounding.

  10. #30
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    Quote Originally Posted by paulockenden View Post
    Off at the controller is 5 degrees. But I think off at the HR92 is off. At least, it's different to setting a 5 degree local over-ride.
    Looks like you're right. I performed a test with an HR92 placed in the freezer to cool it down to see what would happen...

    For the test to work the HR92 still needs to be clicked onto its base (with the black wheel) so I removed that from the radiator as well and set the HR92 to OFF. Sure enough it did not turn on the boiler or open its "valve" even at -10 degrees.

    So anyone setting their HR92's to OFF needs to be aware that this disables frost protection for that room, although to be fair so does the O position on manual TRV's... The difference is its far too easy to accidentally turn an HR92 to OFF when you really just want 5 degrees with frost protect as it is only one click of the wheel further than 5 degrees, whereas on a manual TRV there is usually a lot of rotation past * before you reach O.

    To avoid this it would have been better if you had to turn the wheel to 5 degrees then stop for a moment and turn it again to reach OFF, but since this would require a firmware update for the HR92 (via USB ?) I doubt we'll ever see that at least as an update to existing units.

    Amusingly, I discovered the Honeywell system cannot measure negative temperature properly, giving me an array of weird results once the temperature dropped below 0 degrees... (Also the LCD display started to fade and become quite slow below about -5, but that is typical of this type of LCD)

    The phone app cannot display negative temperatures at all - as soon as it went below 0 the app just displays --. The evotouch attempts to show negative temperatures however the lowest reading I saw was -1.5 even though I know it had got down to about -10. Also sometimes the evotouch reported 99 degrees, then a few minutes later would be reporting -1.5 again.

    The HR92's temperature display gave even more bizarre results - I saw readings including "d9.3", "E0.3", "E2.3" along with the word FROST as the temperature changed. So either those are error codes or the HR92's firmware was never written to cope with negative readings.
    Last edited by DBMandrake; 18th June 2016 at 09:19 PM.

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