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Thread: Evohome Opentherm - tearing my hair out!

  1. #41
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    Quote Originally Posted by paulockenden View Post
    I use SmartThings to trigger various things (save current mode when the burglar alarm is set, switch to eco, push the previous mode back when the alarm is unset, for example). Never seen it cause spurious heat demands, but I don't think I've ever used custom mode.

    P.
    SmartThings with Evohome? Or am I misunderstanding? Probably the latter.

  2. #42
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    Just like some of us use IFTTT or Domoticz to trigger stuff on Evohome, Paul uses Smartthings. I really wish IFTTT could obtain feedback from Evohome too, that way a lot more could be acheivement, rather than simply one way instructions. But at least now with webhooks, many IFTTT actions can be hung off a single trigger.

  3. #43
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    Quote Originally Posted by G4RHL View Post
    SmartThings with Evohome?
    Yup. I was on the original beta, but ended up using David Lomas's (codesaur) third party integration. It isn’t perfect, but it usually works.

  4. #44
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    Morning all,

    hope everyone's enjoyed the sun! What an odd bank holiday

    So, I'm coming to the conclusion that EvoHome is just bad when it comes to keeping temps normal when it's not quite cold enough. After lots of watching the boiler and temps what I'm seeing is that a zone may be at setpoint, but to keep it there EvoHome may set it's pin at 15/100, this isn't enough to actually let any water through (even though each TRV has had weeks to get that right), but in all honest I don't expect them to be that accurate. The issue however is that EvoHome I don't believe shows a % draw at this level for any lentgth of time, to 'keep' a rad at setpoint I'm guessing that it just asks for a quick burst of heat every 10 mins, the annoying thing is that it keeps asking for 50degrees+ rather than taking any real advantage of OpenTherm.

    The ideal of OpenTherm seems to be a long way off with EvoHomes implementation of it. It seems to feel like OpenTherm is a delicate instument that you can play well, and EvoHome is a drunk in a bar on a piano, ocasionally hitting something gentle, but often just smashing all the notes..

    I'm still not happy about this, so want to dig more... does anyone know if I get an HGI80 can I use it just to monitor all EvoHome traffic? Or will it have to replace the wifi controller as master?

    thx

  5. #45
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    Quote Originally Posted by billytkid View Post
    Morning all,

    hope everyone's enjoyed the sun! What an odd bank holiday

    So, I'm coming to the conclusion that EvoHome is just bad when it comes to keeping temps normal when it's not quite cold enough. After lots of watching the boiler and temps what I'm seeing is that a zone may be at setpoint, but to keep it there EvoHome may set it's pin at 15/100, this isn't enough to actually let any water through (even though each TRV has had weeks to get that right), but in all honest I don't expect them to be that accurate. The issue however is that EvoHome I don't believe shows a % draw at this level for any lentgth of time, to 'keep' a rad at setpoint I'm guessing that it just asks for a quick burst of heat every 10 mins, the annoying thing is that it keeps asking for 50degrees+ rather than taking any real advantage of OpenTherm.

    The ideal of OpenTherm seems to be a long way off with EvoHomes implementation of it. It seems to feel like OpenTherm is a delicate instument that you can play well, and EvoHome is a drunk in a bar on a piano, ocasionally hitting something gentle, but often just smashing all the notes..

    I'm still not happy about this, so want to dig more... does anyone know if I get an HGI80 can I use it just to monitor all EvoHome traffic? Or will it have to replace the wifi controller as master?

    thx
    I still think that you might be asking too much of your system. As Honeywell developed the Opentherm protocol and designed Evohome, one would expect these two bits of kit to play nicely. The great unknown is how have the various boiler manufacturers designed their boilers to work with Opentherm when the protocol itself is a bit like Woolworth's 'pick and mix'. As reported many times on this forum, boilers from various boiler manufacturers end up with different results when under Opentherm control. For example, on my boiler, manual setting of the max CH flow temperature appears to be disabled under Opentherm.

  6. #46
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    The HGI80 is simply used to interact with the controller. It's not designed to replace it, although it can, but I wouldn't recommend that. So yes, by all means get an HGI80 to monitor traffic, but these days with the Heat Demand displayed on the controller the business case for that purchase is weak. Also you will need Domoticz, and I can tell you now that the OT Heat Demand implementation on Domoticz is not right, simply because Dan doesn't have OT.

  7. #47
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    Also bear in mind that you are also using a VR33 which is converting from OT <-> eBUS. Studying the Heat Demand is fine but at the end of the day, it's what your boiler sees and does that matters.

  8. #48
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    Quote Originally Posted by billytkid View Post
    So, I'm coming to the conclusion that EvoHome is just bad when it comes to keeping temps normal when it's not quite cold enough. After lots of watching the boiler and temps what I'm seeing is that a zone may be at setpoint, but to keep it there EvoHome may set it's pin at 15/100, this isn't enough to actually let any water through (even though each TRV has had weeks to get that right), but in all honest I don't expect them to be that accurate.
    If the pin travel reported by the HR92 is sitting at 15 then there won't be any water flowing through the radiator and there won't be any heat demand sent to the boiler for this zone. The radiator will be cold, and this all implies that the room is maintaining it's set point without any heat from the radiator - what's wrong with this ? Sounds like it's working as expected to me ?

    If the weather is warm and the set point can be reached without any heat from the radiator, why would you want the radiator to be warming up ?
    The issue however is that EvoHome I don't believe shows a % draw at this level for any lentgth of time, to 'keep' a rad at setpoint I'm guessing that it just asks for a quick burst of heat every 10 mins,
    No, if the pin position of the HR92 is only 15, it will not ask for any heat from the controller, and the controller will not ask for any heat from the boiler, unless some other zone is requiring heat. There is no "quick burst of heat every 10 mins" from a zone that is below a 30 pin position.
    the annoying thing is that it keeps asking for 50degrees+ rather than taking any real advantage of OpenTherm.
    What was the heat demand shown in the diagnostic screen when the boiler reported 50 degrees ? And are you certain that is the requested flow temperature, and not the current flow temperature of the boiler ? If it's actually the measured flow temperature then the issue is probably just that the boiler can't modulate it's output down low enough when only one or two radiators are drawing a small amount of heat. So the Evohome might ask for 40 but the temperature ends up creeping up to 50 due to the lack of modulation. (And then at some point the boiler will shut off if it can't modulate low enough, so the boiler will end up cycling on and off even though the Evohome might be asking for a low, constant flow temperature)
    The ideal of OpenTherm seems to be a long way off with EvoHomes implementation of it. It seems to feel like OpenTherm is a delicate instument that you can play well, and EvoHome is a drunk in a bar on a piano, ocasionally hitting something gentle, but often just smashing all the notes..

    I'm still not happy about this, so want to dig more... does anyone know if I get an HGI80 can I use it just to monitor all EvoHome traffic? Or will it have to replace the wifi controller as master?
    An HGI80 with Domoticz can monitor all traffic including heat demands across the system, it does not "replace" the wifi controller as a master.

  9. #49
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    If all your rads are at 15/100 there should not be any Heat Demand at all. Is the setting screen actually showing Heat Demand for any zone where the pin is 15/100? Are you in a position to track the Flow Temperature requested, compared to what you are measuring the actual Flow Temperature to be?

    On my 438 boiler, I have fixed my max KW output to be 18KW (note my boiler doesn't have the AUTO) - and I can see my boiler modulating between 5.1KW and 18KW. If I kept it on it's max of 38KW, then it only modulates between 6.8KW and 38KW. So in setting my max to 18KW, my boiler appears to behave like a 418 which can modulate to a lower load. Might be worth trying that.

    Another option might be to rent my recent purchase for a short while. An OT gateway. Or get your own. That will allow you to track not just the Requested Flow Temperatures but also the Actual Flow and Return temperatures of the boiler, because the VR33 is reporting these back to the OT Bridge. You can then graph this data in Domiticz and see what is going on. The only thing missing is catching the Heat Demand messages. For that you will need to either buy an HGI80 or build one.

  10. #50
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    hi all,

    thanks again for the replies, hugely appreciated.

    I agree at position 15 there shouldn't be any heat demand, but I am seeing some. I've ordered an HGI80 to try to get to the bottom of this, this should arrive for the weekend.

    @DBMandrake - re the calling for heat point. It's a good question, I'm monitoring the flow and return temps from the pipe directly into Domoticz so this could be an overshoot in theory, but take a look at the attached. The boiler is able to modulate to 45degrees when it wants.

    @bruce_miranda - I've set my partial load to 20KW, down from 35KW, I can go lower. However... how does the boiler know what is partial v full load? Does it just look for a delta between flow/return to make this choice? I set my boiler to Auto partial load and the DHW didnt get hot quick enough, as I assume it changes KW based on these values.
    Where can I get an OT gateway? I'd happily plug this in, I use Domoticz for running my house anyway.

    Also, here is another graph from today:
    chart (1).jpg
    It does seem to again 'blast' for heat then stop, then do it again, rather than go slow and long. Or, could this be (looking at flow/return temps) the boiler waiting for F/R to balance? It sees happy when return stays at 40 degrees, but is odd it takes an hour to get to this point of being happy. But then, again, EvoHome keeps calling for heat even after it's hit the temp - shouldnt it know it was close enough and pull back?

    Thanks all

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    Last edited by billytkid; 8th May 2018 at 04:51 PM.

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