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Thread: Random Niggly Issues

  1. #11
    Automated Home Legend
    Join Date
    Sep 2014


    It's probably the well known (?) HR92 bug where it sends a periodic set point update to the controller even if you don't adjust the control. I don't recall if it is every 30 minutes or every 60 minutes.

    If it happens to send this periodic update just after a set point change is scheduled but before the 4 minute set point update to the HR92 is sent, it gets interpreted as a manual zone override by the controller. For example:

    The set point is scheduled to go from 5 degrees to 20 at 6pm, (Assuming optimal start is disabled) but the 4 minute transmission from controller to HR92 to update it's set point isn't due until 6:03pm. Through bad luck the boot-up time of the HR92 means that it's hourly set point refresh to the controller is due to be sent at 6:02pm. The sequence of events is:

    6:00pm - controller displays the scheduled change to 20 degrees but it will not send this new set point to the HR92 until 6:03pm

    6:02pm - the HR92, still being set at 5 degrees sends its hourly set point refresh to the controller - informing it that it is set to 5 degrees. The controller interprets this as a manual override to 5 degrees because the current scheduled temperature is different - eg 20 degrees. (Even though it "knows" that it didn't send the set point update to the HR92 yet - that is the bug)

    The temperature displayed on the controller is now 5 degrees again with the pocket watch manual override icon since it received the override from an HR92. The override time lasts until the following set point.

    6:30pm - the controller now sends the most recent set point - 5 degrees, to the HR92. Now this becomes a zone override for the whole zone.

    The window of opportunity is at most 4 minutes because the HR92 has to send its set point update after the controller's schedule changes but before it has sent the change.

    The workaround is to simply do a battery out reboot of the HR92 to change it's hourly timer not to fall within one of these narrow windows of opportunity.

    The only problem with this is manual overrides made through the controller or phone app can also suffer the same fate of being "reverted" by this bug. I very occasionally see my manual overrides made through the controller of phone app being reverted to the old temperature a few minutes later but retaining the override end time. The interesting thing is that there isn't a lot Honeywell can do to properly fix the bug without a firmware update to HR92's.

    At most they can mitigate it. The mitigation would be something like:

    Controller reaches a set point change or a manual override at the controller is made. If, before it gets a chance to send that set point update to the HR92, it receives a set point change from the HR92 for the previous set point and the new set point has not yet been sent out, ignore this set point change. It's only a mitigation though, not a 100% fix.
    Last edited by DBMandrake; 15th November 2016 at 12:40 AM.

  2. #12
    Automated Home Ninja Mavis's Avatar
    Join Date
    Oct 2014
    North East


    Quote Originally Posted by paulockenden View Post
    I think I saw a random override the other day too. Just thought I'd probably messed something up, bit now seeing this I'm less convinced.
    That is the frustrating thing, the randomness and the not being sure if you have done anything.

    Thanks DBMandrake, another comprehensive clear answer that explains things (I like to know the whys and rationales).

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