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Thread: Evohome set an override by itself - linked to comms fault?

  1. #1
    Automated Home Guru
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    Default Evohome set an override by itself - linked to comms fault?

    Noticed a comms fault on the panel this morning, for that zone it is showing an override of 20C set (normally 12 is the programmed value). Wasn't sure if this was a a reporting glitch so went to the room in question.

    The room has two HR92s and a dedicated thermostat unit. One HR92 was completely dead, the other and the thermostat were running fine.

    The radiator with the still-working HR92 was indeed on full blast. I actually have no idea how long this has been the case, if it's been heating an unused room long-term that's not good!

    Can anyone shed any light on this? The fact the main controller reports the override makes me think it's not a rogue HR92?

  2. #2
    Automated Home Legend paulockenden's Avatar
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    Perhaps the dead HR92 died when the room was last heating up, and just after sending a 100% heat demand?

  3. #3
    Automated Home Guru
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    If you have multiple HR92s in a zone you set one as master, but if you also have a thermostat is this still the case, or does the controller talk to the thermostat? If the latter, it should be controlling the still-alive HR92 at the last program?

    Doesn't explain the override on the controller either.

    Also - I never thought of this buy can you get email notifications of battery/actuator issues like you can service failure/restoration?

  4. #4
    Automated Home Jr Member
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    The override showing on the main controller when nobody set an override, is a well known problem. I get it fairly regularly on a system with 11 HR92s.

    If the central unit sends a temp setting to the HR92 but the HR92 doesnt get it -then when occasionaly the HR92s send their current temp setting to the central controller, the controller interprets the difference as a manual override and sets it accordingly.
    - this daft behaviour is because unbelievably Honeywell implemented a comms protocol without units acknowledging each other.

    - this normally sorts itself out when the central controller sends the next set point to the HR92 (assuming it gets it) so unlikely its been heating the room for a long time.

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