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Thread: Central Heating randomly turning on when it should be off

  1. #41
    Automated Home Legend
    Join Date
    Sep 2014


    The Kitchen...

    You don't say whether 7c is the set point, measured temperature or both. I'm going to assume it is only the set point, if so what was the current measured temperature ? You also don't say if you have one or multiple HR92's in the Kitchen zone. I'll assume one.

    If it happens again go into the menu on the HR92 and change option 10 to 1, then note down what the valve position is. Refer to my graph here:

    A heat demand of 7% implies a valve position of about 43%, so if you find the valve position is actually 0 (fully closed - which it should be if the set point is more than 2 degrees below the measured temperature) then the problem is either a lost comms message from the HR92 to the controller, or the HR92 is misbehaving and not sending heat updates properly.

    I've had the latter happen to me on occasions - where the HR92 otherwise works normally and the signal is strong but it doesn't seem to send heat demand updates to the controller properly - they get "stuck" permanently on a previous value. I've had this problem even mean that I turn the HR92 up and it opens the valve but won't fire the boiler... (as the heat demand is still stuck at 0)

    For this problem the solution for me was to remove the batteries from the affected HR92's to reboot them.

    If the cause is a lost comms message then the heat demand will eventually right itself and the boiler will go off (after maybe 30 minutes) as the HR92 will send another heat update, but it may keep happening from time to time if there is intermittent comms.

    So my suggestion would be to remove and refit the batteries in all HR92's in the affected zone, (while you're there make sure the connection is good, battery contacts are a weak point in the HR92) and see if it happens again. If it does, note down the heat demand at the controller and the valve pin position reported by the HR92 and let us know.

  2. #42
    Automated Home Sr Member
    Join Date
    Jan 2012
    East Sussex


    Many thanks for the tips and all your assumptions were correct.

    The Kitchen rad was quite cool so I think the valve was shut plus my poor boiler makes a different noise when all the HR92's are shut (I guess the bypass valve or just the pump feeling unhappy).

    Thus started with the easy option of removing the AA's for a while.

    I shall see what it does tonight...

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