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Thread: Evohome - large temperature overshoots

  1. #11
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    Quote Originally Posted by willcurrie View Post
    I'm not using the optimisation as it doesn't suit my system. For the first few days I has some big overshoots but it soon settled down and now generally is spot on.
    Thanks. I hope my system does the same as I'm having massive trust issues with it at present. Came home tonight and my house is a bit on the toastie side. Heating is set to 21, but all zones (8 of them) were 21.5 and above. All rooms downstairs were 23 and it feels uncomfortable.

    Seems there's a lot more effort to get this system working than I'd hoped. I guess I need to play around with Optimised Stop, Temperature Offset on the HR92s and maybe changing temperature to 20 instead of 21 (as a last resort).

    I have thermometers in my rooms downstairs, and with the old fashioned heating system with standard thermostat set to 21 in hallway, all rooms seemed to maintain a nice 21. Now I just keep seeing them at 23.

    I'm beginning to lose confidence with this kit which is a shame as it's taking all the fun out of having it installed and this whole kit cost me a lot of money (for me anyway)

  2. #12
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    I'd suggest setting your room targets a touch below your ideal then leave it to bed in for a few days. once it's settled down you can try some of the other settings. Change one thing and evaluate the change over a few days then move onto the next. You will be happy with your system in a few days once it's happy with your house.

  3. #13
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    I would not loose confidence. It works and it works well. Just make sure everything is all properly set. I switched off optimisation as there seemed to be little advantage to it, it was bringing heating on too early and often would short cycle. The system does work well.

  4. #14
    Automated Home Legend paulockenden's Avatar
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    Quote Originally Posted by f1arp72 View Post
    All rooms downstairs were 23 and it feels uncomfortable.
    Are the rads in radiator cabinets, or do they have furniture pushed up against them? Is there a free flow of (normal room) air around the HR92s?

    If not you might be better off with a DT92 controlling the room temp rather than relying on the rad valves.

    P.

  5. #15
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    Optimisation as far as I know does not influence the precision of how a room is heated. It changes when the systems comes ON or goes OFF. But it shouldn't make a difference in precision.

    @paul: I would expect the HR92's to heat too quickly when there's no free air flow, which would actually cause undershoots instead of overshoots.

    @f1arp72: I hope leaving it running/learning for some time will fix it for you. I have personally tried Evohome 18 months (2 winters) and it has always continued to overshoot big time for me (only to cool down and then overshoot again). I have given up on it myself and am using a very simple cheap thermostat now, that keeps everything nicely around the desired temperature. However, there's other folks here who don't have these problems, so it might start working fine for you as well!

  6. #16
    Automated Home Ninja Mavis's Avatar
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    Now spring is here, our sitting room (south facing) gets a lot hotter but the heating still comes on. I think, as someone else has mentioned there should be the facility to have different season schedules. In winter, I have found that room temperatures are much more straight forward in the winter as the external temp and sun heat on windows are very low. Now it is spring the sun radiation has a bigger influence in the room

    I have optimisation still switched on and the OPT Off at this time of year kicks in at least three quarters of an hour before the setpoint so the heating 'switches off' around 9.40pm (with a night setpoint of 10C at 10.30pm) There is no noticeable difference in the temp.

    I now have my IFTTT geofencing recipe switched on all the time (to turn on Economy Mode when I leave the house and on when I return - I work Mon to Fri) and the rest of the family have not complained that the house is too cold. I guess I should really change the schedule so that there is only a burst of heat in the morning and then around 6ish in the evening.

  7. #17
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    Quote Originally Posted by erik View Post
    @f1arp72: I hope leaving it running/learning for some time will fix it for you. I have personally tried Evohome 18 months (2 winters) and it has always continued to overshoot big time for me (only to cool down and then overshoot again). I have given up on it myself and am using a very simple cheap thermostat now, that keeps everything nicely around the desired temperature. However, there's other folks here who don't have these problems, so it might start working fine for you as well!
    @eirk: So have you abandoned the Evohome system completely then and replaced with an old fashioned thermostat?

    @Mavis: I agree outside temperatures are now possibly having an effect but we've not reached 23 outside yet, and last night it definitely wasn't that warm outside when I got home? I guess under "old" conditions I'd have heating switched off now and wouldn't be "worrying" about what my heating system is doing


    I just can't get my head around this system. Woke up this morning and was told by Evohome that both rooms downstairs were 19. However, standard thermostats I have sitting in each room were showing 22 and 21 meaning the rooms did not require heating. However, Evohome came on and started heating them. Surely there can't be a 3 degrees difference between the height of a table top thermostat and the floor where the rad valves are ??

    If I was to guess given on how the room "felt", I would believe the 22 of the thermostat as opposed to the 19 of the Evohome rad !!

  8. #18
    Automated Home Legend paulockenden's Avatar
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    Quote Originally Posted by f1arp72 View Post
    Surely there can't be a 3 degrees difference between the height of a table top thermostat and the floor where the rad valves are ??
    Why not put your old fashioned thermostat near (or even standing on top of) the rad valve?

    P.

  9. #19
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    @f1arp72: Have you perhaps inadvertently adjusted the Temperature Offset on the HR92 TRVs? It's parameter 8 in the Parameters menu. If you have Parameter 8 set to -3, then this would explain your symptoms. I would then try returning back to 0 and then monitor it for a couple of days.
    In my experience the HR92s do a good job of estimating the temperature, but can struggle when a room takes a while heating up. In those cases it will over-read. I solved this in one of our rooms by adding a DT92E room thermostat. I haven't seen them under-read however, unless the Parameter 8 is set to a negative number.

  10. #20
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    Quote Originally Posted by paulockenden View Post
    Why not put your old fashioned thermostat near (or even standing on top of) the rad valve?

    P.
    Yeah, I thought of that and will give it a go tonight. Thanks

    Quote Originally Posted by Bazinga View Post
    @f1arp72: Have you perhaps inadvertently adjusted the Temperature Offset on the HR92 TRVs? It's parameter 8 in the Parameters menu. If you have Parameter 8 set to -3, then this would explain your symptoms. I would then try returning back to 0 and then monitor it for a couple of days.
    In my experience the HR92s do a good job of estimating the temperature, but can struggle when a room takes a while heating up. In those cases it will over-read. I solved this in one of our rooms by adding a DT92E room thermostat. I haven't seen them under-read however, unless the Parameter 8 is set to a negative number.
    Thanks for the suggestion but no, parameter 8 is untouched and set to zero. I think this may be to do with the fact the rad valve isn't in the greatest position (in lounge under window) so I'm probably getting the colder air coming through window and falling on to rad valve? I do like the idea of maybe switching to a DT92E if I can't find another solution. Would I have to delete the zone then recreate with DT92E. I presume I have to somehow bind the DT92E to the HR92 ?

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