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

  1. #131
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    I have got this to now work in a "Hybrid" set-up.

    For some reason my boiler, a Vaillant ecoTec Plus 438 open vented, won't fire up simply via eBUS issued by the VR33 (assuming it is issuing that command). I use the term eBUS because the VR33 is nothing but an OpenTherm to eBUS converter. However the VR33 does seem to be talking to the boiler. When I install the VR33 module I can see the boiler d.90 change from 0 (eBUS unidentified) to 1 (eBUS identified). Also when I remove the OT jumper on the VR33 module the target temperature as seen in d.09 goes down to 10C. When I put in the jumper the d.09 jumps to 70C, which is what I have set the maximum temperature to be on the boiler knob.

    When I connect the Evohome Opentherm bridge the d.09 changes based on heat demand. Values I saw were 90 when there is HW demand, 53 when there is normal CH demand, 74 when there is a lot of CH demand, 40 when there is low CH demand. Pressing the Evohome Opentherm bridge button toggles the target between 90 (on and full) to 10 (off).

    So I knew the heat modulation was working between Evohome and the boiler. But I still couldn't fire the boiler up when there was demand.

    Luckily I had not changed the old zone valve wiring and that was still in place. So I connected the 230V heat demand wire back to terminal 4 on the boiler (as it would have been in a normal 230V S plan set-up).

    So now the actual boiler firing is triggered via the old S plan wiring (micro switches in the motorised zone valves) and the various BDR91 controlling the motorised valves themselves. But the target temperature to get to is set by the OpenTherm bridge.

    It all seems to work just fine and didn't cost me any more. All the original safety features are still intact and I didn't need to change the wiring a lot. Infact even to move to using two BDR91 to control the motorised valves, I simply swapped the old honeywell timer to two BDR91, one for HW and the other for CH.

    I'll report back in a little while how things are looking but a massive thanks to top brake, StuartG, Paul and Richard for getting me this far.

    I guess if I wanted a complete eBUS boiler firing then I'd need to invest in a Vaillant wiring centre but for the moment I cannot see the need to do so. The main aim for me going down the Opentherm route was to get the boiler to modulate based on demand, and I think that purpose has been satisfied.

    P.S. I'd be very keen to know how StuartG's boiler works completely on eBUS when Vaillant themselves insist that the wiring centre is required. I'll put this down to the age of the boilers and mine having some kind of the limitation to only talk eBUS via the wiring centre.
    Last edited by bruce_miranda; 11th April 2016 at 01:46 PM.

  2. #132
    Automated Home Legend top brake's Avatar
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    Quote Originally Posted by bruce_miranda View Post
    Are any of you using the VR65 or VR66 wiring centre?
    According to Vaillant you will need a wiring centre to use ebus controls with the 400 and 600 series’ ecoTEC boilers.

    I dont have this. I simply have a 230v Honeywell S plan wiring box.
    no i do not have vr65 or vr66
    I work for Resideo, posts are personal and my own views.

  3. #133
    Automated Home Legend paulockenden's Avatar
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    Have you tried bridging terminals 3 and 4 (which I think should force the boiler to 'on')? Is the opentherm stuff then able to switch it off when not needed?

    P.

  4. #134
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    You can buy an ebus to usb converter and query the boiler from a Raspberry PI or similar using ebusd - I am using it to monitor flow/return etc.

  5. #135
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    I've been following this thread closely.
    I have a brand new 2016 ecoTec Plus 835 ErP

    Despite Vaillant telling me & my installer it will never work.
    We followed the quite frankly simple steps, you very helpful people have provided here.
    We installed the VR33, bound the wireless bridge it really was as simple as that.

    * Remove 240v thermostat wires
    * Install module, plug in cable from X31 on mainboard to X32 on module.
    * Bridge burner off
    * Bridge RT24
    * Wire from OT T to Wireless bridge
    * Turn everything on & bind

    I've read people have issues binding modules & valves but I got everything bound first time.

    Here it is working. I guess we'll see how it performs over the coming weeks/months.
    Thanks to all who contributed to this thread

    2016-04-11 23.24.16.jpg
    2016-04-10 22.08.37.jpg
    Last edited by pixxelbob; 12th April 2016 at 12:18 AM.

  6. #136
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    Quote Originally Posted by paulockenden View Post
    Have you tried bridging terminals 3 and 4 (which I think should force the boiler to 'on')? Is the opentherm stuff then able to switch it off when not needed?

    P.
    I didn't leave the boiler in this bridged configuration for long. Maybe I should have done. What I did see was the boiler was on even when there was no call for heat and stayed on. It fired until the max temperature was reached and then just cycled. You could see the icons on the boiler saying there was a call for heat.

    Also to be perfectly honest, I prefer my Hybrid system. Because that way I am sure that the boiler is being fired by a zone valve only after it opens. I didn't like the fact that zone valves and boiler firing were going to be controlled independently in an ideal set-up (am old school and not at least when RF communications is involved). I did notice that the Opentherm bridge was quicker to react to a change that the BDR91s getting their command to open.
    I now have a system that could always act as a non Evohome system, should it need to. I just need to put the time clock back and turned off.
    Last edited by bruce_miranda; 12th April 2016 at 10:27 AM.

  7. #137
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    Does Evohome still do TPI when the boiler is being controlled in this way?

  8. #138
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    What do the light-blue quarter-circles on the Evohome controller mean? I've never seen that before...

  9. #139
    Automated Home Legend paulockenden's Avatar
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    Quote Originally Posted by rotor View Post
    What do the light-blue quarter-circles on the Evohome controller mean? I've never seen that before...
    Where on the controller?

    http://www.automatedhome.co.uk/vbull...on-colour-mean

  10. #140
    Automated Home Legend top brake's Avatar
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    Quote Originally Posted by rotor View Post
    What do the light-blue quarter-circles on the Evohome controller mean? I've never seen that before...
    this is in the screen saver, means that the set points are low temp range
    I work for Resideo, posts are personal and my own views.

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