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Thread: evohome & outside temp & window sensors

  1. #1

    Default evohome & outside temp & window sensors

    Hi All

    Hoping to give some clarity on a few things.

    Windows sensors
    You do not need to buy the window sensors with the HR92. We get this question a lot. The older TRV's (especially in Europe, where there are compliance rules) had the option of a wired sensor which would detect if the window was open. The HR92 does not need this as it has a fuzzy logic computer which after learning the signature of the room can detect the same 'effect' an open window or abnormial ventilation is occuring. This setting can be tweaked in the deep settings of the HR92.

    Outside Temp
    Due to the optimisation routines, learning and rooom by room sensing & control - any outdoor weather sensing is redundent, other than to provide insight. There is a legacy optional add on sensor - but this has no impact on how evohome operates. This is because you have to understand that in the 'old' days the learning capabilities, room by room sensing and the clever boiler throttling that can be achieved, were not available. A sudden cold weather front coming in, is irrelevant. What is relevant is the room temperature and how evohome achieves the target temperature. It could be -5 dropping to -10 but your house could be insulated well, so at what point does evohome decide to act? On neither actually - its what happens inside the home is what it cares about. There is a direct correlation to the outside temp and the inside of your home. But the inside of your home has a different heatup/cool down signature to any outside measurement. If your rooms inside the home drop below X then it will act. Or a new schedule is due to kick in and it knows that it needs to achieve Y, then the optimisation will kick in. Based on the signature of the room, even if a cold snap comes in, the evohome will act based on what it knows it should do to recover. IT is constantly monitoring. It could be suddenly -5 and snowing outside, but due to insulation your room could be comfortable for many hours. There are settings for the optimisation - ie have mine limited to 2 hours pre start for instance, which is more than enough ( a highly insulated room might be 1hr) .

    It is interesting to note in Germany, most of their houses operate with outside weather control on their heating. The market is starting to adopt evohome with no boiler control (becuase it would be too intrusive to remove the weather control and set evohome up to control the boilder), and evohome controls the system in exactly the same way, but without the boiler 'firing'. Their systems can detect valves opening remotely on the heating system, so this generates the 'demand' for heat. So they get the SmartZoning and let the boilders operate as normal. (They especially like becuase of the balancing nature - ie a cold day but sunny on one side of the house) In the UK (and other countries) we dont have this system, which doesnt matter as evohome is capable of controlling the heat source, via a BDR.

    I hope this helps - In summary It would be impossible for a fully embedded evohome system that had learned the home and was SmartZoned to be 'caught by surprise' by any weather temperature shift. The weather (and forecast) appears on the app to provide additional information to the user.

    (PS Humidity is a big factor on how people 'feel' - Whilst I see my system tells me on days like today its 21 degrees, it feels colders due to the 93% humidty, so yes of course treat yourself to a 'burst' of comfort if needed, but usually the temp is correct. )
    Last edited by Rameses; 26th November 2014 at 09:45 AM.

  2. #2
    Automated Home Guru
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    Thanks for this very useful insight into the evohome. For those of us with a "techy" background, this sort of addition to the evohome documentation (in a "techy" appendix perhaps?) would be invaluable.
    Cheers

  3. #3

    Default

    Understand. Let me post up some other resources. Standby
    getconnected.honeywell.com | I work for Honeywell. Any posts I make are purely to help if I can. Any personal views expressed are my own

  4. #4
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    A couple of questions if I may
    1) Windows sensors - I have the HRUK80. Do these respond to the window open? I have them set on the controller but cant say I have ever noticed them shutdown as I normally have to go and manually shut down the valve when the off-spring leave a window open
    2) On average, how long does evohome home take to "learn" a zones optimisation requirements? I have had previous thermostats with optimisation in which I found the optimisation multiplier. Each day it would optimise once in the morning and if it missed it added 1 to the multiplier. As I discovered the house had a multiplier of around 35 in early winter, to get to the correct optimisation value it took 35 days!! As soon as the weather changed and it started missing again it would add 1 to the number. In deep winter the multiplier was 50. So that took another 20 days of misses to get to the correct optimisation. When the weather warmed up the reverse happened. I would imagine evohome home uses much more sophisticated algorithms but am curious as to the approximate learning time. My new system has been in 2 weeks and it has taken this time to start hitting the temps on time. Does this sound about right? The HR80s on the rads are the same units I had in when I had the previous mark I monochrome evohome controller for 2 years. I have just upgraded to the Mark II colour controller and believe the optimisation is in the controller and not the HR80s. Therefore, the new controller would have to re-learn the zones optimisation requirements? (I hesitate as something I read when first installing the Mark I unit made me think that the HR80 carried out the optimisation logic unit but as a computer programmer it didn't seem the logical place to me)

  5. #5

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    1) Yes it does (sorry read the question wrong first time) - but it doesnt have the extra parameters, to allow to tweak it. Hr92 does have these.
    2) 7-10 days. I remember exactly when it happened - it was odd it felt like the house got 'balanced' and the motors become barely noticable.
    Last edited by Rameses; 27th November 2014 at 02:22 PM.
    getconnected.honeywell.com | I work for Honeywell. Any posts I make are purely to help if I can. Any personal views expressed are my own

  6. #6
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    Quote Originally Posted by Rameses View Post
    1) Yes it does (sorry read the question wrong first time) - but it doesnt have the extra parameters, to allow to tweak it. Hr92 does have these.
    2) 7-10 days. I remember exactly when it happened - it was odd it felt like the house got 'balanced' and the motors become barely noticable.
    Thanks, I need to get an extra few rad controllers now that I have the extra 4 zones to play with so will try the 92s. The optimisation time sounds about right then for my new unit and yes it all did suddenly feel balanced yesterday as you observed with your set up

  7. #7
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    Red face Deep Setting of HR92, or any Evo part for that matter

    Hi Rameses,

    I see you'd posted about "deep settings" of the HR92 but I couldn't follow your references to "see posts elsewhere"... sorry!

    Are there any "deep settings" ? I've been looking for the missing manual on Evohome rather than all the standard published Honeywell literature, and I can't find any guides on a service-level setting for any Evo components. Of course there are all the usual parameters that can be set, but is there really a lower level for technical staff. I've seen that linux guys are programming their own devices to go deeper, but I'd like to stick to the standard components for the moment.

    I really want to lock TRVs off for the whole duration when windows or doors are opened, and the window-function only works for 30 minutes, from memory. This means I have to use a BDR relay to use physical wiring techniques for each of these rooms to get the hard level of control needed to make the occupants realise that there is only ever heating when windows and doors are shut !

    Also the single/multi-room options on the controller do not allow for multiple temperatures to be set all under one time-zone. When the house is partly occupied by a work-at-home person on three mornings a week then that "Work-Zone" should ideally control the downstairs loo at 15 as well as the study at 21. And yes, we'd like to avoid the faff of defining two zones for the purpose and then having to copy the times/days from Loo-Zone to Study-Zone !!

    Such things....

    Do you think there is a deeper level of control than the standard manuals suggest ?

    Cheers,

    George.

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    So, if a zone is programmed to be 20C in 3 hours time and the zone is currently 14C, Evohome optimised start will behave exactly the same regardless of whether the weather is (a) 5C outside (having suddenly plunged) and the wind is howling or (b) 16C outside (having suddenly warmed up) and still? I would have thought that it would take much longer to warm by 6 degrees in the first scenario than the second, because the heating has to work just to maintain the existing temperature in the zone.

  9. #9
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    Quote Originally Posted by Rameses View Post

    It is interesting to note in Germany, most of their houses operate with outside weather control on their heating. The market is starting to adopt evohome with no boiler control (becuase it would be too intrusive to remove the weather control and set evohome up to control the boilder), and evohome controls the system in exactly the same way, but without the boiler 'firing'. Their systems can detect valves opening remotely on the heating system, so this generates the 'demand' for heat. So they get the SmartZoning and let the boilders operate as normal. (They especially like becuase of the balancing nature - ie a cold day but sunny on one side of the house) In the UK (and other countries) we dont have this system, which doesnt matter as evohome is capable of controlling the heat source, via a BDR.
    The weather control often acts at the boiler changing the maximum setpoint, that's the maximum water temperature the boiler would provide. My boiler has it installed (I'm in Italy, not in Germany), I just have to turn it on at the boiler (now I turned it off because it seems to be clashing with the OpenTherm control, on an on/off control system it should be fine). In such a configuration you could set up your boiler to be "always on" (provided you have a good bypass valve) and the internal thermostat would stop the burner as all radiator valves are shut. So, unless you have a noisy boiler (as I do ... ) you can do without boiler control.

    "Old style" zoned systems had no need for a boiler relay since the heat demand was usually picked up from the zoning valves, that used to have an end-run switch. This kind of set-up would benefit from weather compensation, as usually the zone valves were driven by independent programmable thermostats that didn't "learn" room signatures.

    You can easily retrofit such a system with EvoHome using BDR91s to control zone valves (and some Y87RF or DT92 as temperature sensors), or switch to a radiator controlled system (based on HR92s), but the latter is more intrusive, you'll have to lock zone valves in the open position. No big deal would be to add a BDR91 to control the boiler in such a scenario (just attach it to the old valve switch).

    I followed these two steps to adopt my EvoHome, and added another step in which I replaced the on/off boiler relay with an R8810 OpenTherm gateway. Now I have a fully modulating, radiator controlled system. The OpenTherm interface will be the subject for another post...

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