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Thread: Using an unbound HR92 as a regular TRV

  1. #1
    Automated Home Sr Member
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    Default Using an unbound HR92 as a regular TRV

    The rad in the airing cupboard has an HR92 on it, but I just want the airing cupboard to have the opportunity to heat up whenever something else decides to fire the boiler. I thought the latest firmware update might let me do it, but I can't see how. If I unbind the HR92 will it work like a regular mechanical TRV?

  2. #2
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    If it's unbound can you just leave it at the temp you want?

  3. #3
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    Quote Originally Posted by IanIreland View Post
    If it's unbound can you just leave it at the temp you want?
    That's what I'm asking. I can't find anything to tell me whether the temperature comparison (set vs actual) and driving of the stepper motor is done inside the HR92 (and that it works even if unbound) or whether it needs the controller to command the stepper to move ... hoping that someone here does. If not I'll suck it and see.

  4. #4
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    Could you try it?

  5. #5
    Automated Home Jr Member
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    AIUI there is connection between the temperature sensor and the valve control stepper motor in the HR92.
    Far easier to put the original TRV sensor back on the valve if you still have it.

  6. #6
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    Why are you wasting money on an electronics device to do what the mechanical one would do?

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    Quote Originally Posted by DorrisMancer View Post
    That's what I'm asking. I can't find anything to tell me whether the temperature comparison (set vs actual) and driving of the stepper motor is done inside the HR92 (and that it works even if unbound) or whether it needs the controller to command the stepper to move ... hoping that someone here does. If not I'll suck it and see.
    Yes - if you unbind an HR92 (it will show unbound at the bottom instead of a zone name) it will operate autonomously as a manual TRV.

    No scheduling of course, set it to one temperature and it will stay at that temperature forever to the best of its ability, given that it can't call for heat from the boiler, so just like a mechanical TRV in that regard, just one that is a lot more accurate at maintaining that temperature.

    I actually bought a single HR92 and used it for a few months before I bought an Evohome controller, so I know this works.

    Be sure to delete the zone it was originally bound to in the controller (if it was the only HR92 in the zone) or rebind the other HR92's if there were other ones in the same zone to ensure that the controller itself also no longer believes that HR92 is bound - it's probably not enough to just clear the binding at the HR92 end.
    Last edited by DBMandrake; 28th March 2018 at 07:51 AM.

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