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Thread: How to use evohome with reversible heat/refresh heat pump?

  1. #1
    Automated Home Jr Member
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    Question How to use evohome with reversible heat/refresh heat pump?

    Hello

    I'm still using Evohome since more than 5 years and I'm happy with it.
    I'm going to replace my old boiler by an air/water heat pump (Erset C11) that is able to refresh in summer.

    I'm also replacing my radiators with a heat floor.
    I noticed that the heat floor controller HCC80 is compatible with heating/cooling, and also the single zone thermostat t87rf2 or DT90, but no mention on the evohome controller...

    Does anybody knows how it works?

    I want also to add in each bedroom radiator with integrated fan to boost the cooling effect, can I control it with the THR92?
    https://www.google.com/url?sa=t&rct=...0PVis6TMXQH89h

    Will it work also in cooling or the valve will close and prevent the system to work?

    Any help is highly welcomed!

    Eric

  2. #2
    Automated Home Legend paulockenden's Avatar
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    Heat pumps and underfloor heating (especially when heating a slab) are a bit like night storage heaters, but perhaps even more laggy. You need to predict when cold or hot days are going to happen and adjust the settings to suit. Evohome isn't designed for that - its control logic is designed around fairly fast moving (in a thermal sense) radiators. I'm not convinced that it's suited for a heat pump / underfloor system.

  3. #3
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    Not only that, Evohome only supports heating, it doesn't have any control logic for cooling, or switching a reversible system from heating to cooling.

    So totally unsuitable for the stated application.

  4. #4
    Automated Home Jr Member
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    Evohome HM80 does a great job of maintaining single zone UFH temperature compared to the BDR91 I used before.

    Temperature maintained within 0.2C over 4hrs this evening.

  5. #5
    Automated Home Jr Member
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    Quote Originally Posted by paulockenden View Post
    Heat pumps and underfloor heating (especially when heating a slab) are a bit like night storage heaters, but perhaps even more laggy. You need to predict when cold or hot days are going to happen and adjust the settings to suit. Evohome isn't designed for that - its control logic is designed around fairly fast moving (in a thermal sense) radiators. I'm not convinced that it's suited for a heat pump / underfloor system.
    That's a very good point, but it should depends how the system is architectured. If the HCC80 is the slave actuator of the evohome then it will work as you describe, but the HCC80 can be an autonomous underfloor controller, so I guess that it is responsible of the regulation loop (PID) and that the evohome is only configuring the temperature set point.
    I found a datasheet that seems to indicate it works like that with an older controller
    https://heatingcontrols.honeywellhom...on/pdf/955.pdf (last page)
    If it works like this it should work right?

    Many thanks for the answers.

    Eric
    Last edited by courcirc8; 26th December 2019 at 03:02 PM.

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