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Thread: Evohome single zone with BDR91 zero or very near zero overshoot anybody

  1. #1
    Automated Home Jr Member
    Join Date
    Oct 2020
    Posts
    19

    Default Evohome single zone with BDR91 zero or very near zero overshoot anybody

    Hi Folks, I have been running Evohome in a single zone configuration driving a BDR91 and using the HCF82 remote sensor for a year. The sytem works fine except for temperature overshoot which is a major issue for me. It always oveshoots by somwhere between 0.5 & 2.0C. My configuration is about as simple as it gets yet Evohome refuses to learn/accept I do not require overshoot and I do not need more heat when the set point has been met. My alternative non Smart thermostat using simple TPI leaves Evohome for dead on temperature control & overshoot. There are many threads on this subject with lots of folk thinking oveshoot is a design feature while others see it as design failure, I am of course in the latter camp. So is there anyone with a similar simple set up to mine that does NOT suffer from overshoot and poor temperature control ... If so I would much appreciate your story !

    Other possibly relevant info and thouights

    Well insulated house
    Boiler return tep 55oC
    Thermostat that gives great control & near zero overshoot is Drayton Digistat (outstanding piece of kit)
    Of course Evohome is overkill in my configuration BUT is a configuaration that Honeywell recommends.
    Are my expections on overshoot and stable control to high or do I need to continue with my far cheaper unit to get the performance I require.


    I look forward hearing your success stories in taming the Overshoot !!

  2. #2
    Automated Home Jr Member
    Join Date
    Jan 2019
    Posts
    25

    Default

    I canít necessarily comment on the accuracy/resolution on the Drayton Digistat as I have never owned one.

    I can talk about my experiences with Evohome though.

    I have 12 zones and the temperature control accuracy varies by zone. Itís is relatively poor (+1.5 deg) in areas where the thermostats are not installed in optimal locations, I.e behind curtains etc. but significantly better in more open areas. Also after overshooting it then quickly adjusts to the set point and maintains it in a stable fashion.

    A degree or two on start up really doesnít bother me, itís the zoning that I care about.

    The problem with any learning device is that of the conditions are not steady state I.e the weather changes or doors that are normally closed are open, the learning isnít going to be accurate

  3. #3
    Automated Home Jr Member
    Join Date
    Oct 2020
    Posts
    19

    Default

    Thanks for sharing your experience and good to hear you are happy with your system. If I had 12 zones and managed to contain overshoot to 1.5 deg I think I would be happy as well but 1 zone and +2 deg just sucks. The Drayton unit is pretty much perfect yet has to learn nothing to manage that but of course is not Wifi connected with all the advantages that brings (when the servers are up & running)

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