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

  1. #201
    Automated Home Ninja
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    Mar 2017
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    Quote Originally Posted by mdurkin View Post
    I’ve got to be honest, I’m pretty unimpressed with this behaviour. It’s not just in advance of the zone valves, it does it after the valves are closed as the zones shut down in the evening - I watched it this evening. It sat there with full demand via opentherm for a while with all the valves closed.

    I think my easiest option is to put back the ‘orange’ wire that is the feedback to the boiler (to pin 4 from memory) and remove the jumper on 3 to 4. This will shut off the boiler when no valves are open. I probably could find a switched output for the pump, but as my boiler is a system boiler, I don’t really want to looking for something that is designed to be self-contained within the boiler.

    I’ll probably put this back in place. Later when i get time I might wire a hot water priority - right now I see little modulation of heat, so it’s heating the water effectively. I thought I had read that evohome modulates up the heat during hot water demand. If that is the case hot water priority would be better so that the tank is heated as quickly as possible before switching back to CH only (and presumably a lower demand via opentherm). Call me a cynic, but does this actually work (different opentherm temperature demand when there is hot water heating requirements)?
    I also found this the case when using the boiler relay. I found that it was firing the boiler when there was no demand for long periods (up to 4 minutes) before and afterwards. See thread - http://www.automatedhome.co.uk/vbull...elay-behaviour

    I found as I had altered the Number of cycles and minimum on time that it was causing the boiler relay behave this way. After changing this I have found the issue seems to have reduced, and there only being a few seconds in delay between the boiler relay switching on and the heating valve BDR91 switching on.

  2. #202
    Automated Home Legend
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    Jul 2014
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    Yes it does work and it was my Hybrid OT method before I figured out I needed a jumper at 7-8. Remove the jumpers from 7-8 and use the valves to fire the boiler between 3 and 4. The Target temperature will still be varied by the OT but the boiler will fire via the traditional method.

  3. #203
    Automated Home Jr Member
    Join Date
    Jun 2016
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    11

    Default ...any further thoughts?

    Quote Originally Posted by paulockenden View Post
    Depends how the vote goes in June, I guess. But as long as we remain in the EU then fitting a part imported from the Netherlands really shouldn't affect a warranty claim, and like Top Brake says it would be an interesting day in court if they decided to refuse a claim.
    As I read this thread researching OpenTherm along with my new Valliant ecoTec 838/Evohome installation, I came across this post.

    Wondering if anyone's views have changed on what the installation of a VR33 might do to my 7 year Valliant warranty or if, indeed, the VR33 is now available in the UK (my Googling may be off today, but a search only came up with the source in the Netherlands). I am guessing the answer is as clear as everything else in this, ahem, cluster****.....?

  4. #204
    Automated Home Legend
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    Jul 2014
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    The VR33 is a part made by Vaillant. It's just not made available to the UK market.

  5. #205
    Automated Home Lurker
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    Aug 2017
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    I am considering buying the OT bridge for my Evohome system, however I need assistance in determining if my boiler will be a goer. I have a Glow Worm Flexicom 30 SX. The following states that the boiler is unofficially compatible when using the correct VR33 module:

    https://myboiler.com/opentherm/opent...pable-boilers/

    Further reading from the below article suggests that the compatible module will be a AWB OPENTHERM MODULE 0020036768.

    https://myboiler.com/opentherm/vaillant-opentherm/

    Can anyone confirm either way from the below image of the boiler's PCB if this is correct?

    20190616_182808.jpg

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