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Thread: Unusual Evohome HR92 behaviour due to battery fault

  1. #1
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    Default Unusual Evohome HR92 behaviour due to battery fault

    Hi,

    I haven't actually been monitoring my Evohome system too closely recently as I've been spending so much time messing with software. However, I'd noticed occasionally over a couple of months that the HR92 in one room seemed to not be able to close the TRV when it had reached or exceeded the setpoint. The zone had large temperature under/overshoots and I tried reinserting the batteries, removing re-attaching to the TRV, but it still seemed to struggle to control the temperature. I'd also tried manually closing the TRV by turning the adapter and it seemed to close and open OK. Upon closer inspection, it appears that the batteries had a fault and although they showed 2 bars on the HR92 battery gauge, they were causing the HR92 to restart every time it attempted to switch on the motor, or part-way through opening/closing the valve. After inserting fresh batteries, the HR92 seems to be working perfectly.

    Dan

  2. #2
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    Check and increase the battery contact tension on the bottom contacts. I've had the same problem on two HR92's - spontaneous reboots when the motor tries to turn or when the device is bumped.

    It's caused not by faulty or low batteries but by a high resistance connection on the battery contact which is probably moved slightly when the body of the unit twists. New batteries will disguise the problem as the new batteries will have a higher under load voltage and might possibly have slightly different dimensions on the positive button on the battery that makes a better connection, but the underlying issue is the contacts, which are too soft and lose their tension over time.

  3. #3
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    Thanks for the info about the battery contacts, I'd forgotten about that issue. I've just tried increasing the contact tension, but it didn't seem to help and it continued to restart. Maybe the batteries' charge is too marginal, as I've also just tested them in another HR92 and it's done exactly the same thing.

  4. #4
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    Sounds like your battery is genuinely faulty then!

  5. #5
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    I know this is an old thread. But I just noticed that the controller now has an icon for zone low battery, not just a warning message.

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