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Thread: Evohome + Opentherm v Evohome + Boiler Outside Weather Compensation

  1. #71
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    Quote Originally Posted by bruce_miranda View Post
    Ok stay with me for a little longer because I am again confused.

    Firstly the Sundials - System Devices have been removed from the new Wifi evohome controllers.

    Lets assume you had two radiators and one HW cylinder. These were previously connected via an S Plan system.

    The HW motorised valve opened when the HW was needed. The CH motor valve was opened when the radiators were needed. These were generally controlled from a 2 channel time clock.

    Now you were upgrading to evohome.

    You put two HR92s on the radiators. You put the HW kit in.

    How would you connect the two BDR91s in a way that when the HW was needed, it would open the HW zone valve and fire the boiler. And when either of the two HR92s needed heat, it would open the CH zone valve and fire the boiler?

    I thought the only way to do this was to wire the HW BDR91 to the HW zone valve and bind it as the HW acuator.
    Wire the CH BDR91 to the CH zone valve and bind it as the Boiler Demand relay. The reason being, there is was no single acuator for all heating demands coming from the various HR92s except for using the Boiler Demand Relay function.
    I am waiting with interest for the answer as well. If I go into the new Device Settings, there are 3 options: Boiler Relay, Opentherm and None. None does nothing, and I do not have Opentherm. With Boiler Relay configured, the motorised valve opens when I turn up the target temperature, and the motorised valve closes when I turn the target temperature down. With HW set to On, the motorised valve for the HW opens and CH valve stays closed.

  2. #72
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    Quote Originally Posted by HenGus View Post
    I am waiting with interest for the answer as well. If I go into the new Device Settings, there are 3 options: Boiler Relay, Opentherm and None. None does nothing, and I do not have Opentherm. With Boiler Relay configured, the motorised valve opens when I turn up the target temperature, and the motorised valve closes when I turn the target temperature down. With HW set to On, the motorised valve for the HW opens and CH valve stays closed.
    And this is how I thought it was supposed to work. That was until people said there is a way to configure the BDR91 to open the CH zone valve for ANY heat demand from the various HR92s, WITHOUT using the System Devices->Boiler Demand->Boiler Relay option.

  3. #73
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    Quote Originally Posted by bruce_miranda View Post
    And this is how I thought it was supposed to work. That was until people said there is a way to configure the BDR91 to open the CH zone valve for ANY heat demand from the various HR92s, WITHOUT using the System Devices->Boiler Demand->Boiler Relay option.
    I recall having this discussion with my Honeywell-trained installer. There were two options: one, was to de-activate the CH zone valve, remove it or disable it in the OPEN position. Two, was to use the existing CH zone valve controlled via the BDR. I think that he went for Option 2 because it was easier to do. I recall as he flashed through the settings he mentioned boiler on times and cycle rates. No mention was made of a third way and I can find no reference to it in the installation guide. Heating and HW have been working fine for 5 days now.

  4. #74
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    @HenGus Can you please confirm how your system is wired and bound.

    As I understand your HW BDR is bound as the HW acuator and that switches on the HW zone valve, which in turn fires the boiler via the wired junction box.

    Your CH BDR is bound as a System Device->Boiler Demand->Wireless Boiler Relay. That switches on the CH zone valve, which in turn fires the boiler via the wired junction box.

    But as if you are sure that the CH zone valve doesn't open when your HW only is requesting heat then surely there is a difference between using a Wireless Boiler Relay as opposed to an OpenTherm Bridge. @top brake is sure that the OpenTherm bridge fires the boiler for ANY heat demand rather than what you are seeing where HW and CH are being opened independently.

  5. #75
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    My system is as you describe. Two motorised valves and 2 BDRs. The HW BDR was part of the HW kit connected to an unvented system. When Paul suggested that something was amiss, I went up stairs with controller in hand and turned on the HW. The BDR light illuminated and the valve opened. The HW valve remained shut. I repeated the exercise with the Htg BDR and the valve motored and the HW valve remained shut. At this point, it got tricky as both outlet pipes were hot.

    I have just been up again. The HW is ON on the Evohome timer and the BDR green light is ON. The Htg BDR green valve is OFF and the CH motorised valve is closed. As I type, the Hot water has just reached temperature, the BDR green light has gone OFF and the motorised valve has closed. The pump and boiler have shut down.

  6. #76
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    Quote Originally Posted by bruce_miranda View Post
    I thought the only way to do this was to wire the HW BDR91 to the HW zone valve and bind it as the HW acuator.
    Wire the CH BDR91 to the CH zone valve and bind it as the Boiler Demand relay.
    NO! Please see the diagrams I posted earlier. You've described something half way between the conventional and alternative methods.

    The 'official' way is to wire the CH BDR91 to the CH zone valve, as you've described, but then bind as as the heating demand valve, not the boiler relay.

    Alternatively, wire that BDR directly to the boiler, and bind it as a boiler relay. But if you do this you MUST latch the CH valve open.
    Last edited by paulockenden; 4th April 2016 at 06:06 PM. Reason: Typo

  7. #77
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    Quote Originally Posted by paulockenden View Post
    NO!

    The 'official' way is to wire the CH BDR91 to the CH zone valve, as you've described, but then bind as as the heating demand valve, not the boiler relay.
    But HOW? That's the question I've been asking for a while now. Please tell me which menu in the new Wifi evohome system should I use to bind the CH BDR91 as a heating demand valve which will trigger when ANY radiator needs heat. As mentioned the Sundial option has been removed from the System Devices.

  8. #78
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    Quote Originally Posted by paulockenden View Post
    NO! Please see the diagrams I posted earlier. You've described something half way between the conventional and alternative methods.

    The 'official' way is to wire the CH BDR91 to the CH zone valve, as you've described, but then bind as as the heating demand valve, not the boiler relay.

    Alternatively, wire that BDR directly to the boiler, and bind it as a boiler relay. But if you do this you MUST latch the CH valve open.
    So where exactly is the 'heating demand valve' setting in the wifi Evohome set up menu?

  9. #79
    Automated Home Legend paulockenden's Avatar
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    In guided setup it asks you to bind them both (along with the temp sensor).

    you chaps may have your CH BDRs double bound - as both CH relays *and* boiler relays.

    This is incredibly common, and Richard mentions it on his evohomeshop pages.

  10. #80
    Automated Home Legend paulockenden's Avatar
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    Alternatively I think you can do it from the System Devices menu. Set boiler control to none, and then go through the Stored Hot Water configuration.

    Don't forget to clear the existing bindings on the BDRs (15 second press).
    Last edited by paulockenden; 4th April 2016 at 06:16 PM. Reason: More bloody typos

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