Originally posted by DBMandrake
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Ideal Vogue & Opentherm via Honeywell T6 Lyric (wired version)
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Originally posted by richardc1983 View PostI thought opentherm controlled the pump also.
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.
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Originally posted by dty View PostNo, 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.
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
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Originally posted by Strat789 View PostI 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
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.
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Originally posted by richardc1983 View PostIdeal 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 PCB’s 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?
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Originally posted by Strat789 View PostI 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.
If somebody could be bothered to cross-reference the message IDs, then this table would probably help: http://otgw.tclcode.com/matrix.cgi#thermostats
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Originally posted by blowlamp View PostDo 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?
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Originally posted by richardc1983 View PostIs this what it does? Hence constant cycling as boiler than can’t modulate quick enough.
Does your system modulate properly once it's close to its setpoint?
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Originally posted by blowlamp View PostDo 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?
Once the TSet Calculated equals TSet Max, it stays there until all the zones are within a 2C range of their target temperatures. The boiler TSet Calculated temperature then reduces. For most of this afternoon, with all 12 zones at their target temperature, the boiler has operated in a flow/return range of 52 to 55C/ 40 to 45C. The only time that TSet Calculated rose was when my wife increased a zone temperature by 2C. It fell back within 10 to 15 minutes.
No short cycling here when TSet Calculated was close to TMax Set. I appreciate that we are not talking like for like here. Different boilers and different controls - albeit, both Opentherm.
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Originally posted by Dan_Robinson View PostThe OpenTherm controller won't be able to affect the ramp rate of the burner.
My thoughts are that they have messed the boiler pcb up and are sorting it but not taking all the blame.
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Precisely.
Boiler logic varies, and the ignition rate is also different and can affect micro loads if the burner is chucking out 7kW into a rad that can only take 500w.
Some boilers have return sensors, others do not. There are also all sorts of different heat exchanges, burners, fans etc.
As such there is no way a universal controller would/should have direct control over the gas side of the boiler. It can/should only have influence over the flow temperature. The better boilers too will have their own ability to limit flow temp - Intergas being one, Vaillant another, where Tmax can be limited in the boiler software.Kind Regards - Dan Robinson (Jennings Heating Ltd)
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