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Thread: Evohome Wiring Layout for Independent Zone Control

  1. #1
    Automated Home Lurker
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    Default Evohome Wiring Layout for Independent Zone Control

    Good evening,

    I have spent some time researching this subject but am yet to find a robust answer, so I'm turning to the knowledgable community on the topic of Evohome wiring! Its my first post, so be nice...

    I am in the process of designing a new heating system for our house renovation which is currently underway, and plan to install Honeywell's Evohome system. The system will include 3 zone wet underfloor heating, central heating with HR92 TRV's in all rooms and hot water via an unvented cylinder.

    The plan is not to use Honeywells HCC90R UFH controller, but a Heatmister UH4 instead. My understanding is that this means the 3 BDR91's for the corresponding 3 UFH zones wireless thermostats are wired as zone valves to the Heatmister UH4 wiring centre. Fine until this point...

    However the twist is that I want to utilise the Evohome controller as a thermostat for one of the UFH zones. This would mean wiring the corresponding BDR91 into the associated zone on the wiring centre - but what about the radiator wiring? If the Evohome controller is the red box in the proposed wiring layout below, and wired to both the zone for the UFH and the radiator terminal, then how can independent control for these be maintained?

    i.e if the UFH zone calls for heat then the radiator zone valve will open (not a problem as the HR92 TRV's will be shut) but if a radiator calls for heat then the UFH zone will be opened? This is where I am stuck.

    Apologies if I have misunderstood something or this is answered elsewhere, but I have been pulling my hair out over this! I want to ensure I understand the system correctly before committing to purchase and install.

    Many thanks
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    Last edited by Hopelet01; 15th October 2020 at 08:26 PM.

  2. #2
    Automated Home Sr Member
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    Iím sorry but I canít seem to view your diagram.

    Why use Heatmiser at all? If you donít want to use HCC80 you can instead control each zoneís actuator by a BDR91. Then use a T87RF, DTS92 thermostat or EvoHome itself as the sensor in each zone. Simple.

    You use another BDR91 or OpenTherm bridge as your boiler control.

    And the hot water kit BDR91 controls the hot water valve, opening it and shutting any CH valve if you want DHW priority heating.

  3. #3
    Automated Home Lurker
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    Hi Kevin,

    Thank you for your response and apologies for the delay in coming back to you.

    You have simplified it one stage further beyond what I thought possible - good suggestion. The only reason I am using the Heatmister is to have a physical connection to the boiler, and means all electrical connections are made within the same unit. Just preference on my part.

    The main take away for me is that my proposed layout is feasible

    The wiring diagram I plan to install is shown on pages 6/7 of the manual below:

    https://www.underfloorheating.co.uk/...127465/UH4.pdf

  4. #4
    Automated Home Sr Member
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    I think the recommendation according to the installation manual, when you have HR92s, is to have a wirelessly connected BDR91 or R8810 boiler control, not a wired connection.

    You can still use your UFH wiring centre for controlling the actuators and pump.

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