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Thread: What would you like to see in evohome? (have your say)

  1. #271
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    That's a great explanation, thank you!

  2. #272
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    Here's something I'd like to see...

    When using OpenTherm, instead of blindly requesting 90C for "hot now, please", allow the maximum to be configurable in the controller, and separately configurable for hot water and heating. Firstly, it would solve the problem some people are having with boilers (such as Viessmann) which ignore the boiler max setting in favour of the OT request. Secondly, it would allow people to have their condensing boilers working much more efficiently - I'm happy to have the highest flow temperature my boiler can achieve when heating the hot water cylinder, but when heating the radiators, I may want to limit the flow temperature to, say, 65C in order to maximise the time the boiler can condense for.

  3. #273
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    Quote Originally Posted by dty View Post
    Here's something I'd like to see...

    When using OpenTherm, instead of blindly requesting 90C for "hot now, please", allow the maximum to be configurable in the controller, and separately configurable for hot water and heating. Firstly, it would solve the problem some people are having with boilers (such as Viessmann) which ignore the boiler max setting in favour of the OT request. Secondly, it would allow people to have their condensing boilers working much more efficiently - I'm happy to have the highest flow temperature my boiler can achieve when heating the hot water cylinder, but when heating the radiators, I may want to limit the flow temperature to, say, 65C in order to maximise the time the boiler can condense for.
    You could extend this concept even further by providing a good weather compensation system entirely in software that integrates properly with zone heat demands.

    You have an internet connected device which knows your street address (in your TCC account) and which has access to online weather data including temperature for your location. (Currently available only in the iOS/Android app, but there's no reason why the controller couldn't obtain this temperature reading for your location as well)

    Take this weather report temperature and apply a standard weather compensation algorithm (offset and slope adjustment) that can be tweaked in the system settings to match your house and use that to calculate the maximum permissible flow temperature for the current outside temperature. Then take your heat demand figure from the various zones and scale the requested heat demand within the maximum permissible flow temperature determined from the outside temperature.

    So the heat demand of the zones still modulates the flow temperature as it does now, however the temperature range and maximum is scaled down based on outside temperature - warmer weather results in the flow temperature for any given heat demand being scaled down proportionally.

    Once the controller has access to an outside temperature reading the code to do all these calculations is pretty trivial and it could certainly be added in a software update to the controller.

    These are the kind of innovations that Honeywell needs to implement to keep ahead of the competition, or keep up with the competition for that matter. There is so much more that could be done just with a software update.
    Last edited by DBMandrake; 29th June 2017 at 12:15 AM.

  4. #274
    Automated Home Legend paulockenden's Avatar
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    Trouble is, zone temps are managed by the TRVs, not the controller. It just sends targets.

    If the controller micro-managed the TRVs rather than giving them autonomy such things would be much easier.

    Talking about weather comp here, obviously. I totally agree with the ability to set Tmax for Opentherm.

  5. #275
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    My wish list:
    1. Support for more than 12 zones per controller (other solutions support 30), I don't want to have to buy another controller.
    2. Future-proof hardware, I'm annoyed I have to buy the WIFI controller version to get firmware upgrades and new features.
    3. Room thermostat with floor probe for use with WUFH - this is a huge hole and causes a lot of confusion when speaking to WUFH suppliers and deciding on floor coverings.

    It would be useful if a sticky was added to the top of the forum with a list of the requests, as it's a slog to go through 28+ pages.

    Heath

  6. #276
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    Quote Originally Posted by HeathU View Post
    My wish list:
    1. Support for more than 12 zones per controller (other solutions support 30), I don't want to have to buy another controller.
    Yes I would have wanted more - at least 14 or more unless there is some sort of controller to HR92 limitation - I have 17 HR92s controlling 21 rads. Never mind the 3 sundry rads I left on manual.

    It would be useful if a sticky was added to the top of the forum with a list of the requests, as it's a slog to go through 28+ pages.

    Heath
    I've asked Rameses before if there could be a schedule of the proposed software fixes and updates so that forum users can see what's in the pipeline. He thought the idea was worthy of thought but nothing came of it. Not that difficult to create but I agree with Heath - 28+ pages of requests and comments needs condensing into a simple sticky/schedule for reference only - no comments.

  7. #277
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    The ability to use wall stats in multi-room zones.

    I have 24 rads. 5 of these are in a single zone called "downstairs" which comprises several rooms that we never close the door between, so it doesn't make sense for them to be on separate schedules, etc., and also helps us squeeze 24 rads into 12 zones. However, the rooms have different thermal characteristics, so I have the zone configured as a multi-room zone so that each rad can look after itself.

    It would be nice to be able to put wall stats in the rooms and bind them (possibly directly, rather than via the controller) to HR92s so that the HR92s still continue to work independently of each other, but get their temperature readings from the wall stat in the room rather from their own built-in sensors.

    Of course, simply allowing more zones would also overcome this as I could have each of the rooms in its own zone with a local wall stat.

    Better yet... (from a software engineering object modelling perspective) separate the concept of schedules from zones. Then I could have a "downstairs" schedule associated with 4 rooms. For my specific use-case I would still need more than 12 zones for this to be useful!

  8. #278
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    Zone names longer than 12 characters. I mean, come on...

    Master Bedroom
    Guest Bedroom
    etc.

    I use "Master Bedrm", but that totally confuses Alexa because whatever I try and say, it hears "master bedroom" (of course) and then can't match it to any zone.

  9. #279
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    Quote Originally Posted by paulockenden View Post
    Trouble is, zone temps are managed by the TRVs, not the controller. It just sends targets.

    If the controller micro-managed the TRVs rather than giving them autonomy such things would be much easier.

    Talking about weather comp here, obviously. I totally agree with the ability to set Tmax for Opentherm.
    I think you're misunderstanding how weather compensation works Paul.

    You don't have to do anything per zone with weather compensation, no "micromanagement" of TRV's is needed - all weather compensation would do is scale the system wide maximum heat demand flow temperature based on outside temperature using a defined relationship. (Which includes slope and offset adjustment to match the characteristics of the house)

    This scales the maximum possible heat output available on all radiators in a way that is proportional to outside temperature. A cold outside temperature allows a high maximum flow temperature, a warm outside temperature allows a lower maximum flow temperature.

    This sets the maximum heat output available at a given radiator, however individual TRV's can further reduce the heat output from their own radiator by reducing the flow through the radiator - just as they do now. Furthermore, low heat demand from all the TRV's in the house can further reduce the flow temperature below the weather compensation calculated maximum.

    Rather than weather compensation setting a cap on the maximum flow temperature (clipping) it would be better if it scales the flow temperature down proportionally - as was discussed in another thread (?) recently.

    The kicker is that it's SO easy to implement with the existing hardware. As long as the outside temperature is known (whether by internet weather report or an actual outdoor sensor) you simply take the heat demand that is calculated for the OpenTherm bridge today, and scale the demand down based on the outside temperature reading before sending it to the bridge. In the UI you'd need to add an option to turn it on and off, adjust slope and offset, and possibly show the current outdoor temperature and requested flow temperature so that the settings can be optimised for the house. While you're at it you might as well throw in a manual maximum flow temperature setting as well, as apparently many boilers need it.

    The right way to think about weather compensation is that it automates what we do now manually - we turn our flow temperatures up in the winter and down in the summer. But it does it on a continuous basis so the flow temperature is always optimal for the conditions.

    That means being able to heat up sufficiently fast if there is a cold snap, and not overshooting constantly if the weather gets unusually warm. Ideal flow temperatures even differ between early morning and evening in spring/autumn, but nobody adjusts it manually twice a day, whereas weather compensation would do that for you.
    Last edited by DBMandrake; 30th June 2017 at 01:12 PM.

  10. #280
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    Quote Originally Posted by DBMandrake View Post
    I think you're misunderstanding how weather compensation works Paul.
    Not really. I was thinking how weather comp would work best with a system like Evohome.

    As you say, traditionally it dials back the flow temperature of the boiler on warmer days, but that's useless for Evohome because the HR92s (or whatever) have 'learned' how to heat a room based on the flow temp they see from the boiler. Start to mess with that and things will get really messy. A bit like how if you adjust your boiler stat you'll start to see overshoots and more ocscillations than normal for a few days on your temp graphs.

    No, with Evohome I think if weather compensation were to be done it would need to be at zone level.

    That way it could take account of how sunny weather affects south facing zones more (thermal gain), whereas cold weather is more likely to affect rooms on the other side of the house.

    But this would require either the controller to micromanage the TRVs (so much more RF comms), or else pass the predicted weather for the next 6h (say) to the TRV, and let it use that to adjust demand. But I suspect the HR92 doesn't have the processing power to do that.

    P.

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