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

  1. #171
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    Quote Originally Posted by bruce_miranda View Post
    If you look up another thread of mine, you'll see that I have recorded a whole range of OT requested temperatures. But in my set up the low temperatures are not used a lot. Having said that the OT bridge used 34C for about an hour today. See graph attached of the OT temperature and the Boiler's flow (max set to 70C)

    Attachment 880
    For your house it might never need to use the really low temps as the heat loss vs heat input was just enough to keep the temps where they needed to be. No point limiting what the boiler can modulate down to though as some houses where 45C is just enough to maintain heat conditions this might be too much heat input and cause overshoots. The bigger the range means there is more control and thus bigger gains for comfort and efficiency if the boiler can use it. In my house I know for sure that 35-40C flow temp keeps the house at a consistent level in spring autumn but in winter it might need to go upto 45C but then modulate between 40-45C.

  2. #172
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    At the moment with how I have the room temperatures set and the warm temperatures it is only calling for heat on a couple of zones. During the day while the house is empty these zones are set to 16 Deg and change to 21 Deg in the evening and first thing in the morning. On both zones the zones overshoot by a couple of degrees and they don't appear to be getting better control from day to day - the control is basically the same each day with overshoots and worse temperature control of zones.

    Bedroom 1.jpg

    Landing.jpg

  3. #173
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    Hi there, I'm new to the forum, but came to this thread after investigating options for Opentherm on a Vaillant EcoPlus boiler. Although my use case is slightly different (I'm trying to sync it with a Nest gen3), I'd be interested in hearing peoples views on this, and how it differs to the EvoHome implementation, as I'm having some issue with the Nest setup, and may look to switch this out if EvoHome doesn't have the same problems!

    My setup:
    Vaillant System boiler
    In-direct hot water tank (megaflo cylinder).
    Zone valves on upstairs / downstairs heating circuits, and on the hot water feed via. the cylinder, and cylinder stat.
    I've wired up my Nest in a hybrid scenario, as per-one of the other posts earlier in this thread, with a 240v feed into the Vaillant 240v input, alongside the Opentherm inputs onto the VR33 board (I've not linked the 24v pins on the boiler). My reasons for doing this were that without this, I can't see how the zone valves would operate and how the boiler would ever shut down in a hot water demand scenario, where the cylinder stat had reached temperature and caused the zone valve (and therefore the 240v to the boiler coming off the back of the zone valve) to drop.. to me the boiler would just keep on running unless I'm missing something here?
    Anyway.. this all works fine for heating, and I can see the boiler fire on heating demand, and D.009 registers a variety of temp's for the demanded flow temp based on inputs from the Nest.
    However, for hotwater - the Nest seems to keep the demanded flow temp down at only 10deg, which means the boiler doesn't flick on or heat the water :-(
    Instead of putting D.009 upto a reasonable value as I'd expected (e.g. 75 deg say - as it does at the start of a heating cycle where there's high demand), the Nest seems to instead push down a change to another Vaillant attribute (I think it's D.0021) which changes Cylinder Charge required from no to yes.
    Nest's implementation seems to be therefore different to EvoHome (can someone confirm please- Evohome triggers a change to D.009 for both Heating and/or hot water?).
    Is anyone aware of anything I can do to change this way of working, otherwise it appears I'll need to step back from Opentherm with Nest, as it doesn't seem compatible with the Vaillant VR33 in the hot water scenario.
    I'm not sure what the Cylinder Charge function is meant to do, or why Nest is changing this attribute vs. increasing the demanded flow temperature. The behaviour is the same even if I attempt to keep the heating under opentherm control, and the hot water on an on/off setup - since this will flick a 240v input into the boiler ok, but the D.009 registered flow temp demanded by Nest still sticks down at 10degrees?
    Anyway - realise it's not the exact nature of this thread, but I'd be interested in others thoughts around this based on their setups here, and whether an EvoHome could fix this setup. Thanks Jonathan

  4. #174
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    Quote Originally Posted by tapgrove View Post
    Hi there, I'm new to the forum, but came to this thread after investigating options for Opentherm on a Vaillant EcoPlus boiler. Although my use case is slightly different (I'm trying to sync it with a Nest gen3), I'd be interested in hearing peoples views on this, and how it differs to the EvoHome implementation, as I'm having some issue with the Nest setup, and may look to switch this out if EvoHome doesn't have the same problems!

    My setup:
    Vaillant System boiler
    In-direct hot water tank (megaflo cylinder).
    Zone valves on upstairs / downstairs heating circuits, and on the hot water feed via. the cylinder, and cylinder stat.
    I've wired up my Nest in a hybrid scenario, as per-one of the other posts earlier in this thread, with a 240v feed into the Vaillant 240v input, alongside the Opentherm inputs onto the VR33 board (I've not linked the 24v pins on the boiler). My reasons for doing this were that without this, I can't see how the zone valves would operate and how the boiler would ever shut down in a hot water demand scenario, where the cylinder stat had reached temperature and caused the zone valve (and therefore the 240v to the boiler coming off the back of the zone valve) to drop.. to me the boiler would just keep on running unless I'm missing something here?
    Anyway.. this all works fine for heating, and I can see the boiler fire on heating demand, and D.009 registers a variety of temp's for the demanded flow temp based on inputs from the Nest.
    However, for hotwater - the Nest seems to keep the demanded flow temp down at only 10deg, which means the boiler doesn't flick on or heat the water :-(
    Instead of putting D.009 upto a reasonable value as I'd expected (e.g. 75 deg say - as it does at the start of a heating cycle where there's high demand), the Nest seems to instead push down a change to another Vaillant attribute (I think it's D.0021) which changes Cylinder Charge required from no to yes.
    Nest's implementation seems to be therefore different to EvoHome (can someone confirm please- Evohome triggers a change to D.009 for both Heating and/or hot water?).
    Is anyone aware of anything I can do to change this way of working, otherwise it appears I'll need to step back from Opentherm with Nest, as it doesn't seem compatible with the Vaillant VR33 in the hot water scenario.
    I'm not sure what the Cylinder Charge function is meant to do, or why Nest is changing this attribute vs. increasing the demanded flow temperature. The behaviour is the same even if I attempt to keep the heating under opentherm control, and the hot water on an on/off setup - since this will flick a 240v input into the boiler ok, but the D.009 registered flow temp demanded by Nest still sticks down at 10degrees?
    Anyway - realise it's not the exact nature of this thread, but I'd be interested in others thoughts around this based on their setups here, and whether an EvoHome could fix this setup. Thanks Jonathan

    Evohome and hot water kit will be perfect for this application I have it at home on my ecotec plus 615 system boiler. I also have vr33 or adapter and Honeywell OpenTherm bridge
    I work for Resideo, posts are personal and my own views.

  5. #175
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    Quote Originally Posted by tapgrove View Post
    Hi there, I'm new to the forum, but came to this thread after investigating options for Opentherm on a Vaillant EcoPlus boiler. Although my use case is slightly different (I'm trying to sync it with a Nest gen3), I'd be interested in hearing peoples views on this, and how it differs to the EvoHome implementation, as I'm having some issue with the Nest setup, and may look to switch this out if EvoHome doesn't have the same problems!

    My setup:
    Vaillant System boiler
    In-direct hot water tank (megaflo cylinder).
    Zone valves on upstairs / downstairs heating circuits, and on the hot water feed via. the cylinder, and cylinder stat.
    I've wired up my Nest in a hybrid scenario, as per-one of the other posts earlier in this thread, with a 240v feed into the Vaillant 240v input, alongside the Opentherm inputs onto the VR33 board (I've not linked the 24v pins on the boiler). My reasons for doing this were that without this, I can't see how the zone valves would operate and how the boiler would ever shut down in a hot water demand scenario, where the cylinder stat had reached temperature and caused the zone valve (and therefore the 240v to the boiler coming off the back of the zone valve) to drop.. to me the boiler would just keep on running unless I'm missing something here?
    Anyway.. this all works fine for heating, and I can see the boiler fire on heating demand, and D.009 registers a variety of temp's for the demanded flow temp based on inputs from the Nest.
    However, for hotwater - the Nest seems to keep the demanded flow temp down at only 10deg, which means the boiler doesn't flick on or heat the water :-(
    Instead of putting D.009 upto a reasonable value as I'd expected (e.g. 75 deg say - as it does at the start of a heating cycle where there's high demand), the Nest seems to instead push down a change to another Vaillant attribute (I think it's D.0021) which changes Cylinder Charge required from no to yes.
    Nest's implementation seems to be therefore different to EvoHome (can someone confirm please- Evohome triggers a change to D.009 for both Heating and/or hot water?).
    Is anyone aware of anything I can do to change this way of working, otherwise it appears I'll need to step back from Opentherm with Nest, as it doesn't seem compatible with the Vaillant VR33 in the hot water scenario.
    I'm not sure what the Cylinder Charge function is meant to do, or why Nest is changing this attribute vs. increasing the demanded flow temperature. The behaviour is the same even if I attempt to keep the heating under opentherm control, and the hot water on an on/off setup - since this will flick a 240v input into the boiler ok, but the D.009 registered flow temp demanded by Nest still sticks down at 10degrees?
    Anyway - realise it's not the exact nature of this thread, but I'd be interested in others thoughts around this based on their setups here, and whether an EvoHome could fix this setup. Thanks Jonathan
    Forgive my ignorance but a few questions.
    If you have a single Nest, how are you opening the upstairs or downstairs CH valves?
    What is controlling the schedule for the HW?
    Vaillant boilers are able to have two separate target temperatures for max CH and max HW. What are your boiler knobs set to for HW? But that comes into play only when you have the relevant eBUS controls and you will see that on d.25. What I don't know is if once the boiler is set to HW heating mode, how is the target flow controlled. The Nest seems to almost be passing the responsibility of setting the target flow temperature when in HW only mode to something else.

    What I can confirm is that if you use Evohome then the controller is able to handle CH and HW heating modes separately and in combination. But then Evohome is assuming that your boiler is a simple single heat only boiler and doesn't have the capability of handling two different loads. So d.25 (Hot Water activation via eBUS control) is constantly set to 1 (Yes).

  6. #176
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    Quote Originally Posted by bruce_miranda View Post
    Forgive my ignorance but a few questions.
    If you have a single Nest, how are you opening the upstairs or downstairs CH valves?
    What is controlling the schedule for the HW?
    Vaillant boilers are able to have two separate target temperatures for max CH and max HW. What are your boiler knobs set to for HW? But that comes into play only when you have the relevant eBUS controls and you will see that on d.25. What I don't know is if once the boiler is set to HW heating mode, how is the target flow controlled. The Nest seems to almost be passing the responsibility of setting the target flow temperature when in HW only mode to something else.

    What I can confirm is that if you use Evohome then the controller is able to handle CH and HW heating modes separately and in combination. But then Evohome is assuming that your boiler is a simple single heat only boiler and doesn't have the capability of handling two different loads. So d.25 (Hot Water activation via eBUS control) is constantly set to 1 (Yes).
    In answer to the Q's:
    I have two nests - one for upstairs and one downstairs. These are controlling the relevant zone valves via the 240v outputs. The downstairs Nest is also set to control the HW scheduling, and opens the HW zone valve on the HW 240v output.
    In reality, I've never ever used the upstairs heating, as the house is very thermally efficient upstairs, and I've not needed it on this winter (since moving in) so I can ignore this at the minute.
    The boiler is all controlled through the LCD panel selections, but the CH and DHW set points are set at 65 degrees in the install menus.
    I've now managed to build an OPentherm gateway and plugged this into a Raspberry PI, so I can see whats going on with the OPentherm comms between the nest and the boiler.
    What I can see is that when HW is called for, the Nest triggers DHW enable to Yes, and also sends a DHW setpoint value (based on the value I set on the Nest thermostat controlling the water). d25 on the boiler flips, based on the DHW enable trigger.
    The control set point, which is controlled when CH is enabled and heat being asked for, stays down at 10 degrees though. The boiler therefore doesn't fire - it obviously ignores the DHW set point values in my system.. which seems fair given there's basically only one circuit through the boiler which controls both DHW and CH (with selection being then done in the system via the zone valves off a single circuit).
    I guess what I need to do is somehow get the CH control set point to reflect the DHW set point whenever the HW is being asked for.. this would then seem to fix my problem.
    I think I'm back to investigating whether I can do this through programming the OPentherm gateway!
    You've confirmed that Evohome takes a different approach, and assumes the boiler is a single load - and obviously controls it all via. just the single control set point regardless of whether CH or DHW is being asked for - unfortunately the Nest has split the two leading to my issues :-(

    Thanks for the inputs
    Jonathan

  7. #177
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    Quote Originally Posted by bruce_miranda View Post
    Forgive my ignorance but a few questions.
    If you have a single Nest, how are you opening the upstairs or downstairs CH valves?
    What is controlling the schedule for the HW?
    Vaillant boilers are able to have two separate target temperatures for max CH and max HW. What are your boiler knobs set to for HW? But that comes into play only when you have the relevant eBUS controls and you will see that on d.25. What I don't know is if once the boiler is set to HW heating mode, how is the target flow controlled. The Nest seems to almost be passing the responsibility of setting the target flow temperature when in HW only mode to something else.

    What I can confirm is that if you use Evohome then the controller is able to handle CH and HW heating modes separately and in combination. But then Evohome is assuming that your boiler is a simple single heat only boiler and doesn't have the capability of handling two different loads. So d.25 (Hot Water activation via eBUS control) is constantly set to 1 (Yes).
    I had a lot of similar questions bruce_miranda and I went on their FAQ section and honeslty it's really well done...
    But All the explanation from tapgrove are really good too but if you need more, for once, i have to say that their website is well done.
    I also had few problems at the beginning but now everything's working fine

  8. #178
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    Quote Originally Posted by Ro- View Post
    Do you know if it is possible to use the VR33 to connect Evohome with OpenTherm bridge to a Glow Worm boiler (Energy 30s)?

    Many thanks,
    Today I had a specialist Heating engineer around to service and set my boiler up because I was having an issue with the low burner. He said that my Vaillant ecoTec plus 438 boiler was actually a Glow Worm boiler simply badged as a Vaillant. So if I could use a VR33 on my boiler, you could try it and see how it goes. But first you need to check and see if you have an edge slot on the PCB that could take the VR33 connection.
    Last edited by bruce_miranda; 4th March 2017 at 02:55 PM.

  9. #179
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    Glow Worm is Vaillant's 'budget' brand. Some boilers have the same internals, but the Vaillant models have better user interfaces and diagnostics. Longer warranty too, usually.

    It's a bit like saying an Audi A3 is the same as a Skoda Fabia.

    P.

  10. #180
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    Quote Originally Posted by paulockenden View Post
    Glow Worm is Vaillant's 'budget' brand. Some boilers have the same internals, but the Vaillant models have better user interfaces and diagnostics. Longer warranty too, usually.

    It's a bit like saying an Audi A3 is the same as a Skoda Fabia.

    P.
    Ahahaha Love the comparaison
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