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Thread: Evohome reset learning on single zone

  1. #11
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    So I have now tried waiting (for over 3 weeks), deleting and then re-binding the zone and turning optimisation off for a week. Last night I turned optimisation back on and what should happen at 0430 this morning? The kitchen radiator came on. Any ideas?

  2. #12
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    I am guessing here but you could delete and rebuild 2 zones and switch the HR92s to see what happens.

  3. #13
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    Quote Originally Posted by guyank View Post
    So I have now tried waiting (for over 3 weeks), deleting and then re-binding the zone and turning optimisation off for a week. Last night I turned optimisation back on and what should happen at 0430 this morning? The kitchen radiator came on. Any ideas?
    this is as expected, it needs to go through learning process. if you want to set a limit to the preheat time you can set this
    I work for Resideo, posts are personal and my own views.

  4. #14
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    Quote Originally Posted by top brake View Post
    this is as expected, it needs to go through learning process. if you want to set a limit to the preheat time you can set this
    But every other zone is responding as I would expect it to. They are coming on at the correct time to achieve the correct temperature by the set point time, despite taking between 2 hours and 30 mins to achieve this.

  5. #15
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    Quote Originally Posted by guyank View Post
    But every other zone is responding as I would expect it to. They are coming on at the correct time to achieve the correct temperature by the set point time, despite taking between 2 hours and 30 mins to achieve this.
    I am not a plumber but it be that this particular radiator is just very slow to heat up? Might there still be an air lock in one the connecting pipes? Occam's Razor.

  6. #16
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    Hi

    Did you get this working in the end? What worked?

    I've got a similar issue - my bedroom rad comes on 1.5 hours before needed but hits target temp an hour before (ie after 30 minutes). Haven't changed much with the rad, though it's just only started coming on recently due to the colder radiator, so it might just not be well adjusting to different differentials. Do we think it should sort itself out eventually?

    Tom

  7. #17
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    Of interest the Nest thermostat has no way of resetting the learning facility - other than deleting all data and forcing it to start again, I can't understand why designers do that...when implementing a more simple rest would be relatively easy in software, probably not designed by real world designers/users

  8. #18
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    After trying all the suggestions above, I just gave up and left it. It was a good few weeks before I checked again as I didn't have the graphing of zones working then (and the baby was beginning to sleep a bit better!), so I don't know exactly when, but eventually it seemed sorted itself out.

  9. #19
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    It takes 12 hours at set point

  10. #20
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    Quote Originally Posted by happy days View Post
    It takes 12 hours at set point
    Not sure what you mean by that.

    I've found optimal start will only make an adjustment of at most about 15 minutes per day - so if your room was up to temperature an hour early then each following day it should in theory start an additional 15 minutes later each day until it was about right. I can see this behaviour in my graphs. It seems to target being up to temperature about 15 minutes before the scheduled time, to err on the side of being ready in time. Most of my zones are up to temperature about 15 minutes early.

    I too used to notice problems with Optimal start getting some rooms up to temperature way too early, like an hour or even an hour and a half early and seemingly not adapting as it should, however in recent times I have not noticed any problems with it, and whether that's due to fiddling around with the system configuration in the meantime (one zone that had this problem now uses a DTS92 instead of the HR92 sensor for example) or the March firmware update I have no idea. But when I recently checked my graphs to see when rooms were meeting their targets everything was fine.

    One thing that can confuse optimal start though, is rooms that struggle to reach their set points even with the radiator on full blast. Our hallway is a bit problematic like this - in colder weather the room will struggle to reach its 20 degree target even with the radiator going flat out, you can see in the graph the temperature rise is a curve that is asymptotic with the desired temperature - it will either only just make or not quite make the target.

    This will cause optimal start to come on earlier and earlier to try to meet the target but if it simply can't reach the target because the radiator output is insufficient (or flow temperature is too low) it will eventually come on as early as possible (the optimal start maximum number of hours setting) in a vain attempt to meet the target.

    The moral of the story is don't set your targets too high in rooms that are under-provisioned in terms of heat output or it will come on really early in a vain attempt to reach an unreachable target, for no real benefit. In our hallway I just drop the target set point to 18 or 19 in winter (and bump the flow temperature up a bit if necessary) so that it is able to reach the target, this prevents it coming on unnecessarily early.
    Last edited by DBMandrake; 14th October 2016 at 11:16 AM.

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