Originally posted by paulockenden
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Opentherm + EvoHome + Viessmann 111-W overshoots
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Originally posted by bruce_miranda View PostDo either of these two boilers bear the OT logo on them?
Are you saying what I think you're saying: if it hasn't got a logo it's potentially not Opentherm certified?
Does your Vailliant have an Opentherm logos?
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Vaillant isn't OT certified and nor is ATAG, if I am not mistaken. However Vaillant have made the VR33, an interface board, that allows communication with an OT device.
I am wondering if by not using the official OT logo they can argue that they aren't fully OT certified. But offer some OT capabilities via their own controls.
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Originally posted by bruce_miranda View PostVaillant isn't OT certified and nor is ATAG, if I am not mistaken. However Vaillant have made the VR33, an interface board, that allows communication with an OT device.
I am wondering if by not using the official OT logo they can argue that they aren't fully OT certified. But offer some OT capabilities via their own controls.
Clearly no engineer on the design team actually used the product at their own home with OpenTherm or they would have discovered the issue.
It seems almost like wilful ignorance and apathy at this point. I'm glad I don't have an affected boiler because I would be hopping mad if I'd paid a couple of grand for a boiler that "supports" OpenTherm only to find that it doesn't work properly and the manufacturer doesn't seem to care one iota...
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Despite the fact that OpenTherm is a creation of Honeywell, it seems to me that the common factor with all these OpenTherm boilers problems is their Honeywell controllers - I just find it strange that all the 'problem boiler' manufacturers seem to be making the same mistake.
Currently, my Remeha iSense controller is showing an outside temperature of 12 degrees whilst requesting a flow temperature of 24.2 degrees - this is to maintain an internal level 18 degrees. So for me, OpenTherm works just as one would expect
Our Intergas HRE 36/30 boiler is weather compensated & OpenTherm controlled, but be aware that the iSense is ONLY OpenTherm with no other connection/control options. I wonder if this makes it better optimised, rather than having to be a universal solution in the way, say, Evohome has to be.
Martin.
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Hi Martin,
Your system does indeed look good from what you're saying, although Opentherm to be fair is just the protocol, and Honeywell seem to have favoured fast warm up times for rooms in their Algorithms/implementation of Opentherm to get rooms up to temp quickly then settle down the flow temps to maintain.
Unless the boiler explicitly allows for weather compensation at the same time as Opentherm control(like yours or a Vokera boiler), its not going to be possible even though it makes sense. it's not integrated with EvoHome for example. (I.e. EvoHome doesn't know about it if it does work independently)
What's your system like with cold rooms, say 3 degrees or so away from set point temp? Does it just use the weather compensation to set a max ch flow temp for getting up to temperature, and then Opentherm modulation takes over from there when within a degree or so of the setpoint?Last edited by StephenC; 3 May 2017, 04:06 PM.
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Originally posted by paulockenden View PostI suspect that if you did try to wire in weather comp to the boiler along with Evohome control it would COMPLETELY screw the latter's learning algorithms.
I'm not sure it always would. It would really depend on the heating compensation curve and gradient vs heat loss and radiator sizing balance.
For example:
If the weather compensation is configured to balance heat loss, radiator sizing, then the learning will have no job to do or very very little, as the radiator temps will adjust up/down to compensate for higher/lower heat loss. If the learning therefore determines EvoHome needs 1hour to warm a room up by 1.5 degrees C, the learning algorithm should figure out daily that the same duration in all seasons/weather is needed. It will be constantly learning reactively in case though for the next heating period to get better (hit set point in time)
That said, a finely balanced wether compensated System is from what I can see (from reading up and crude experience of weather compensation now) aimed at 24/7/365 maintenance of indoor temps, not setback and heat up periods without weather compensation where learning would be relevant. i.e. learning is a crude alternative to weather compensation where it is not available.
Does that make sense? (Thats my logic from what I've seen, and am happy for others with different/better experience to add their thoughts/views)
For what it's worth, I still see even with the issues I've had, that Opentherm is theoretically the better approach and weather compensation is pretty dumb, but basic and probably doesn't cause installers many issues.Last edited by StephenC; 3 May 2017, 06:11 PM.
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It's effectively two feedback loops in one system, both seeking the same goal.
That's normally a recipe for disaster, as they'll both fight each other.
I know that strictly speaking weather comp isn't a feedback loop, but the weather is so random it'll behave like one for much of the time.Last edited by paulockenden; 3 May 2017, 06:11 PM.
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Originally posted by paulockenden View PostIt's effectively two feedback loops in one system, both seeking the same goal.
That's normally a recipe for disaster, as they'll both fight each other.
I know that strictly speaking weather comp isn't a feedback loop, but the weather is so random it'll behave like one for much of the time.
Hi Paul,
I hear you, but I guess I've not used it for long enough to give a more experienced answer other than it seems ok so far....the issue I had was extended setback of rooms taking far too long to warm up because outside was warmer at the time of warmup. That didn't work.
They (should) cancel each other out most of the time, and should mitigate the risk somewhat however, but as I said above some situations don't work.
What are your thoughts to that consideration?
Again to be clear, I believe WC is flawed for anything other than 24/7/365 temp maintenance (which is fine if that's your objective) and this is why I really want to get Opentherm working!Last edited by StephenC; 3 May 2017, 07:03 PM.
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When weather compensation and OpenTherm are used together, I see weather compensation as a kind of 'master volume control' that determines the overall heat requirement & limit of the building at a particular point in time, whilst OpenTherm takes care of delivering that requirement in an efficient way. I look at weather compensation as being higher in the chain of command, because in essence, when it says outside is warm enough, it turns off the heating.
Martin.
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Originally posted by bruce_miranda View PostDo either of these two boilers bear the OT logo on them?
I'm expecting if it was on the boiler to be on the outside or near the OT connections to be clear, so nothing obvious that I can see.
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