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Thread: Hot water sensor battery

  1. #1
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    Default Hot water sensor battery

    A heads up in a way for those who use Evohome for hot water as well central heating (i.e. not using a condensing boiler). It seems there is no low battery warning given when the batteries run out in the sensor. All you get is a message on the panel saying it does not have a connection anymore. This morning I was greated with just that message on the panel but nothing to say the batteries were done, just that there was no connection. In the app there was no temperature readout. I guessed batteries as what were in were the original ones from December 2014. I replaced them. Had to rebind the sensor and then the relay and all is back to normal. It would help though to have a warning like we get with the HR92s when the batteries in those are failing. I think a diary note is needed to replace the hot water sensor batteries every 12 months! Unless my boiler packs up and needs replacing before then - it's 19 years old.

  2. #2
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    Quote Originally Posted by G4RHL View Post
    A heads up in a way for those who use Evohome for hot water as well central heating (i.e. not using a condensing boiler). It seems there is no low battery warning given when the batteries run out in the sensor. All you get is a message on the panel saying it does not have a connection anymore. This morning I was greated with just that message on the panel but nothing to say the batteries were done, just that there was no connection. In the app there was no temperature readout. I guessed batteries as what were in were the original ones from December 2014. I replaced them. Had to rebind the sensor and then the relay and all is back to normal. It would help though to have a warning like we get with the HR92s when the batteries in those are failing. I think a diary note is needed to replace the hot water sensor batteries every 12 months! Unless my boiler packs up and needs replacing before then - it's 19 years old.
    Thanks for the 'heads up'. Out-of-interest, how do you get at the batteries in the transceiver? I couldn't find a guide.

    Edit: Managed it!!
    Last edited by HenGus; 5th June 2016 at 02:44 PM. Reason: addle info

  3. #3
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    I have just changed the batteries on my HW sensor as they have been in over years. The slightly confusing bit is that after replacing the batteries, all seems well. The controller turns on the HW and a temperature is displayed (which I knew to be incorrect). After carrying out a full re-bind the correct temperature is now displayed.

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    Yes, I found I had to rebind the sensor to the relay and then the relay to the Control Panel. It seemed taking the batteries out for a couple of seconds interfered with the connection. Since then though I have had several faults showing up saying that contact has been lost with the central heating relay yet it hasn't for all is functioning as it should. I have never done just a hot water reset and re-bind. When I set it all up I went through a complete sequence as if all was a fresh installation. That I wanted to avoid this time. The times showing when the panel has lost contact with the heating relay are not times when anything would be calling for heat.

    It would be helpful if fault reports also appeared in the app and not just on the control panel. Particularly if away from home.
    Last edited by G4RHL; 5th June 2016 at 06:40 PM.

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    I have just remembered that the parameters also need to be re-set; that is, max temp and differential.

  6. #6
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    I got a comms fault reporting on the on panel for hot water when I changed it out the panel earlier in the year and ultimately replacing the batteries cleared the issue. Agree it would be useful just to have had a low battery warning as I did end up going round the houses to work out what was actually wrong.

  7. #7
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    Changing HR92 batteries is pretty starightforward for anyone not familiar with the Evohome system. I just wonder how a family member would deal with a CR92 battery change. Honeywell should consider providing some maintenance information in their user documentation. It really should't be necessary to call an installer just to change two batteries. I appreciate that the information is in the information guide but I confess that I didn't know that the water heating BDR etc had to be re-set.

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    To those saying you had to rebind the sensor to get it working again after replacing the battery, I doubt this is actually true - I think you're all just being a bit impatient waiting for the devices to automatically sync up again.

    Wireless devices on the Honeywell system communicate fairly infrequently and at scheduled intervals to save battery life by turning off the receiver when not in use. When the batteries are replaced the device will get out of sync with these scheduled transmissions, it can take a while for them to resynchronise - sometimes in excess of an hour. Putting the batteries in and expecting them to be communicating and in sync in a few minutes is not going to happen.

    I notice that if I switch off the power to my boiler wiring centre (which naturally also disconnects the power to the BDR91) for any extended period of time such as a few hours, that after turning the power back on it can take anywhere between about 5 minutes and well over half an hour before the relay comes back on - even though the controller was scheduled to call for heat the whole time that the power was off. And that is with a mains powered device like a BDR91, so battery powered devices can take longer.

    Personally I would fit the new batteries and come back in an hour or two and only then try rebinding if it is not synchronised yet. I highly doubt that Honeywell have designed the unit to lose its bindings due to flat batteries. None of the other devices like DT92 or HR92 lose their bindings due to flat batteries, although they can take a fair while to sync up again if you just fit the batteries and leave them alone.
    Last edited by DBMandrake; 6th June 2016 at 12:28 PM.

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    I would be very pleased if that is the case. Yesterday, I had the batteries in and out in 15 seconds max. The controller showed that the timing schedule was intact and the HW came on 15 minutes later. I then waited 20 minutes to see an increase in temperature but nothing happened. After a full reset/rebind, the temperature increased as I expected. You might be right but it would be helpful to have something, in my view, in the user guide. The guide has a page on changing the batteries in the Controller and HR92s but nothing about the HW kit.

  10. #10
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    Even with the batteries out for only 15 seconds the device will be powered down and lose sync with the controller.

    I doubt that 20 minutes would be long enough to ensure that it had time to resynchronise. Remember that the hot water kit is both an actuator (relay) and a temperature sensor - these are separate devices as far as binding and communication goes and will have different communication schedules.

    Hence why communication with the actuator was working but sensor updates were not yet being received, which would cause the temperature to appear not to be updating. (For a while) I think given a bit more time (maybe an hour) you'd find that temperature sensor readings would start updating again.
    Last edited by DBMandrake; 6th June 2016 at 01:30 PM.

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