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Thread: Evohome BDR 91 time on/off

  1. #1
    Automated Home Jr Member
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    Default Evohome BDR 91 time on/off

    Hi

    I have an Evohome set up( wifi controller) BDR91 with 7 radiators ( no hot water) all working fine ( except when Honeywell servers go down) I am logging temps with Domoticz via web API ( I have no programming experience) and all look good.

    Under switches tab in Domoticz I see EvoTouch, which I assume is the base controller but cant seem to do anything with it.

    Is there any way to log when boiler switches on and off?

    Many thanks

    Mick

  2. #2
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    If you were using an HGI80 or similar then under the Switches Tab you would see at least 2 relays called CH Valve and Boiler. These track the Heat Demand that is being sent to the BDR91. This isn't visible via the Web API. Heat Demand is different to the actual switching of the boiler, which is actually performed using TPI. As it turns out, I have just submitted a PR to the Domoticz project to create additional Zone Relay devices that actually attempt to track the Switching On/Off of the BDR91 i.e. stay in step to the LED Green light.
    Another thing to note is boiler being switched on is different from Flame being On. So generally Heat Demand > BDR91 TPI > Flame On. Sadly, all of this can only be tracked via sniffing the radio signals and not accessible via the web API.

  3. #3
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    Quote Originally Posted by bruce_miranda View Post
    Sadly, all of this can only be tracked via sniffing the radio signals and not accessible via the web API.
    It would be really nice if Honeywell were to expose the web API and make it more functional so that 3rd party tools like Domoticz could add value. This would greatly improve the product by surrounding it with an ecosystem of capable software. One wonders why they've not done so already.

  4. #4
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    To be fair to Honeywell, their HGI80 is meant to be the way approved 3rd parties integrate with Evohome. The Web API is actually not approved but they can't stop it.

  5. #5
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    Bruce_miranda

    Many thanks for your explanation its much appreciated. I have looked for an HG180 but they seem to be a bit thin on the ground do you know of anything similar?

    Thanks again

    Mick

  6. #6
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    At the moment, if I had to recommend another RF capture device it would have to be the NanoCUL or an RFBee. You will have to load some custom firmware on it, which a few of us are developing. If you don't have OpenTherm then the firmware is pretty stable. The OT Bridge is the only device that is causing some issues.

    P.S. I am looking to get rid of a few of my RFBees + UARTBees. PM me if you are interested. I'll load up the firmware on it before I send it out, so you will be up and running straight away.

  7. #7
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    Quote Originally Posted by bruce_miranda View Post
    If you don't have OpenTherm then the firmware is pretty stable. The OT Bridge is the only device that is causing some issues.
    I've been thinking about adding OpenTherm to my setup. What problems are you encountering with the OT bridge? Is there somewhere where you are discussing this?

    Thanks.

  8. #8
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    there is no problem with the OT Bridge itself. It's just that the DIY radio interfaces have the most problems with messages sent out by the OT Bridge. Having said that the success rate is quite high, so nothing to worry about

  9. #9
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    Quote Originally Posted by bruce_miranda View Post
    there is no problem with the OT Bridge itself. It's just that the DIY radio interfaces have the most problems with messages sent out by the OT Bridge. Having said that the success rate is quite high, so nothing to worry about
    Great, thanks. As you've had your OT bridge in place for a few years now, is it something you would recommend based on your experience (I have a Vaillant condensing system boiler, and my DHW is also controlled by evohome)?

  10. #10
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    I have only ever had OT on my Vaillant. I never used Evohome with a BDR91 boiler demand. So I have nothing to compare against. But the fact that I see low Target Flow temperatures when all my zones are at their setpoint gives me hope that I am running a theoretically more efficient system.

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