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Thread: Ideal Vogue & Opentherm via Honeywell T6 Lyric (wired version)

  1. #91
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    Quote Originally Posted by DBMandrake View Post
    Not really.

    If you specify a target flow temperature using OpenTherm the boiler will modulate the burner kW output as necessary to meet and maintain that requested flow temperature.

    If you were to specify a target burner output in kW directly using OpenTherm (which I don't think it can do anyway) the flow temperature that you ended up with would be all over the place depending on the load presented by the radiators, so wouldn't provide any useful control.
    So what do you think ideal are on about then?

  2. #92
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    I read "Burner Output" as the Trigger to fire the burner. How can an OT determine what size the burner output should be? It should just demand a certain flow temperature and maybe have control of when the Burner fires.

  3. #93
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    I thought opentherm controlled the pump also.

  4. #94
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    Quote Originally Posted by richardc1983 View Post
    I thought opentherm controlled the pump also.
    No, the boiler controls the pump.

    My Vaillant will quite happily run the pump without the burner if the demanded flow temperature suddenly drops - i.e. it will circulate the hot water already in the system to meet demand until enough heat has been lost that it needs to fire up the burner again.

  5. #95
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    Quote Originally Posted by dty View Post
    No, the boiler controls the pump.

    My Vaillant will quite happily run the pump without the burner if the demanded flow temperature suddenly drops - i.e. it will circulate the hot water already in the system to meet demand until enough heat has been lost that it needs to fire up the burner again.
    I looked at the OpenTherm Specification: the Master OT Plus (Opentherm Bridge, T6 and Evohome etc) can request control of the Slave (Boiler) Flow rates and the Set Temp. as required. There isn't anything in the Spec. about control of the Slave gas flow.

    Also, in the Specification, it describes the difference between OT Plus (OT/+) and OT Lite (OT/-) - the main difference is: if no (OT/+) handshake is sent back from the Slave to the master (after a control request from the master) the master goes into OT/- mode ie the Boiler is treated as dumb ....a simple on/off system that responds to heat requests from the Master OT.

    In OT/+ Mode: there is loads of monitoring/control data is passed back from the Slave to the Master eg Modulation (status is on/off) Return temp etc etc

  6. #96
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    Quote Originally Posted by Strat789 View Post
    I looked at the OpenTherm Specification: the Master OT Plus (Opentherm Bridge, T6 and Evohome etc) can request control of the Slave (Boiler) Flow rates and the Set Temp. as required. There isn't anything in the Spec. about control of the Slave gas flow.

    Also, in the Specification, it describes the difference between OT Plus (OT/+) and OT Lite (OT/-) - the main difference is: if no (OT/+) handshake is sent back from the Slave to the master (after a control request from the master) the master goes into OT/- mode ie the Boiler is treated as dumb ....a simple on/off system that responds to heat requests from the Master OT.

    In OT/+ Mode: there is loads of monitoring/control data is passed back from the Slave to the Master eg Modulation (status is on/off) Return temp etc etc
    So confusing as this was what originally ideal said:

    The issues they have noticed are, target temp not being reached again due to cycling, overshoot of target temperature due to too high a flow temp and cycling & the boiler off dial not turning the boiler off. Boiler is behaving worse than a standard on off boiler.

    An example of this in my house is: House was sat at 20c at 7.30 this morning when set point was 22c, it had come on at 5am, flow temp was 45c and it was cycling on and off to get the rads hotter to 70c had to turn set point to 24c.

  7. #97
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    Quote Originally Posted by richardc1983 View Post
    Ideal have replied;

    I have spoken to our R&D team again on this query.

    From speaking to them it is apparent that Honeywell opentherm devices control both the flow temperature and the burner output, whereas most only operate the boilers flow temperature.

    This is causing the boiler operating mode to be overridden and hence the issue.

    I have again chased the PCBs needed for your boiler today and am assured they will be with us very soon when I will be in touch again.

    Do you think Ideal might be referring to the way Honeywell OpenTherm devices operate at full burner output until they are within a degree or two of set temperature, at which point they then start to request a specific control flow temperature?

  8. #98
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    Quote Originally Posted by Strat789 View Post
    I looked at the OpenTherm Specification: the Master OT Plus (Opentherm Bridge, T6 and Evohome etc) can request control of the Slave (Boiler) Flow rates and the Set Temp. as required. There isn't anything in the Spec. about control of the Slave gas flow.
    I believe all Evohome does is request the set temperature, but I can’t be certain. I have all the components to build an OpenTherm gateway, but haven’t found the time to do it yet. Once I do, I will know for certain.

    If somebody could be bothered to cross-reference the message IDs, then this table would probably help: http://otgw.tclcode.com/matrix.cgi#thermostats

  9. #99
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    Quote Originally Posted by blowlamp View Post
    Do you think Ideal might be referring to the way Honeywell OpenTherm devices operate at full burner output until they are within a degree or two of set temperature, at which point they then start to request a specific control flow temperature?
    Is this what it does? Hence constant cycling as boiler than can’t modulate quick enough.

  10. #100
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    Quote Originally Posted by richardc1983 View Post
    Is this what it does? Hence constant cycling as boiler than can’t modulate quick enough.
    I think the idea is to get the house nominally up to temperature as quickly as possible.
    Does your system modulate properly once it's close to its setpoint?

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