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Thread: Evohome S plan plus underfloor heating

  1. #1
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    Default Evohome S plan plus underfloor heating

    Evening everyone,

    I have been reading these forums for a while gaining some great ideas for some renovation work Iím doing on my house, but am now a bit stuck. I have trawled through here and the rest of the web and can't find a definite answer to my query so am hoping for some help/ advice.

    I have a system boiler, manifold for the underfloor heating (5 zones) on the ground floor and radiators on the first floor. The system is set up with 2 two port zone valves, one for the manifold and one for upstairs heating.

    I have bought two BDR91 relay boxes, the HCC80R undefloor heating controller, the evohome controller and 4 HR92 radiator controllers. I was hoping that I could control all of this from one evohome controller, however, from what I have read, this is not possible, at least not in the way I would hope.

    For the underfloor heating, the configuration plan in the installation manual when using the evohome controller, suggests that it is the evohome controller that talks to the BDR91 (I assume when the BDR91 is set up as a boiler relay), however, it also appears possible that the HCC80R can talk directly to the BDR91 which I hope can be used to open the zone valve and then I can use the standard set up to configure and control each zone. Has anyone done it like this and is this the way it works?

    For the radiator heating, it looks like I would have to set up the second BDR91 as a Boiler Relay and then configure the system with the HR92's, however I think the implication of this is that every time the underfloor heating zones call for heat, this will also open up the upstairs heating. This isnít the end of the world, but Iím hoping to understand if there is a better way?

    The other option would be to buy another evohome controller, however, I would rather keep the controls central if possible.

    Hopefully someone can point me in the right direction of what i can do?

    Many thanks,

    Jono

  2. #2

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    Providing you are fitting HR92s to all of your radiators then there is no need to control the two heating 2-port valves independently once you've got the new controls installed as you now have zone valves for every room in the house instead. So you could use your Heating Demand BDR91 to operate the UFH and rads 2-port zone valves together (i.e. wire them in parallel to the one BDR), and then any room demand sees both 2-port valves open at once but the flow will only reach the rooms that are calling for heat.

    If you want to keep individual control of the heating 2-ports then your only solution with Evo is to separate the heating and UFH onto separate Evo Touch controllers.
    Sensible Heat
    SensibleHeat.co.uk

  3. #3
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    Thanks Sensible Heat,

    I guess the issue I had with wiring both in parallel is that I am still running water through the main upstairs heating ring when potentially, only the downstairs is calling for heat.

    But as you say, I could always get another Evo Touch controller for upstairs if I wanted to keep them separate.

    Cheers,

  4. #4
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    I have a similar system to the OP with the same question which I am attacking from a different direction.

    Just planning an install for a 4 zone S-plan plus setup where each zone is contolled by a two port motorized valve (top floor, middle floor, UFH on ground floor and Hot water). I am going to use an HCC80R to contol the underfloor heating but have both a 2 port valve and the boiler to activate. CH pump stealing heat from the HW means I want to close my 2 port valves when not in use.

    My intention is to wire a BDR91 relay as the actuator for each valve and leave boiler activation to the existing valve switch which closes when the valve is fully open as happens at present. This should allow me to have a single acutator trigger for each of the 4 zones.

    My 4 UFH zones on the ground floor would then be controlled directly from the HCC80R with the BDR91 opening the valve which triggers the boiler... will this work?

    This would give me 4 UF zones + middle floor + top floor + HW

    My existing UFH contoller (polypipe) can control the 2 port valve directly but I cant run mains through the relay on the HCC80R so need to use a BDR91 relay I think.

    Could someone confirm this is sensible before I buy all the parts and get an electrician in. Unfortunately there don't seem to be any Evohome installers near me (Stockton) so my plumber has recommended a sensible electrician.
    Last edited by OliB; 7th January 2015 at 01:20 PM.

  5. #5
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    You can run mains through the relay on the HCC80R (for the UFH motorised zone valve and UFH Pump), so do not need the BDR91 for this. What you suggest is fine and will work with BDR91's switching the motorised zone valves and the switch wires on the motorised valves giving the boiler demand instead of a demand relay.

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