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Thread: Evohome alternative to HCC80R for Opentherm ?

  1. #1
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    Default Evohome alternative to HCC80R for Opentherm ?

    First time poster.
    I have a combi boiler with a S Plan plus config with 3 zone valves, one upstairs, one downstairs (rads) and one downstairs wet UFH, which is one circuit with itís own pump.
    I am in the process of installing Evohome, currently upstairs only, BDR91 switched live connected to the zone valve. Iím going to do the same with the zone valve for the downstairs radís but I havenít yet got a plan for the UFH for which I know Iíll need a Evohome thermostat.
    I am planning to replace the boiler next year with one that has an Opentherm interface and at that point will buy a R88 Opentherm bridge, rewire and remove the BDR91ís.
    My question is about the UFH, because it has its own 240v pump, it seems like my only option is to get an HCC80R but itís really pricey (approx. £320). Is there any cheaper option out there ? I guess what I need is the ability for the thermostat to have a call for heat to the Evohome controller (which then sends a message to the OT bridge connected to the boiler) whilst simultaneously switching on the pump.
    The boiler will probably be a Veissmann Vitodens 100, I donít know what outputís it has but I guess if it could control the pump externally then that could work expect it would run when there was any call for heat, not just from the UFH.

  2. #2
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    I'm running my UFH pump controlled by a BDR91 relay and as temperature sensor T87RF. However, I don't like the proportional control done on the pump, pump will make it but the relay definitely not.

  3. #3
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    Iím actually just in the process of getting UFH. 2 zones and so Iím going to get HCC80R.

    Iím no expert here, but I believe a single evohome controller can only independently control 2 BDRs (CH and DHW). If you have HRís on all upstairs rads you could bind both BDRs to the CH (both in bind mode when binding the CH BDR), so on any call for heat both would open. You could then wire in the pump in parallel to the UFH BDR, so turning on the pump

  4. #4
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    I wasn't aware that you could bind two BDR's to the controller - I might give that a go for a different issue where I have two zone valves but I'm vaguely aware that this mightn't be a great idea with the TPI functionality of the HR92's. Doesn't solve the Opentherm issue but there's another long thread on the EVOHome Shop forum about the merits of OT and Vitodens 100 which I need to fully digest as maybe that it's not a great option.
    https://theevohomeshopforum.co.uk/vi...ee26e6521b1f7f

  5. #5
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    I moved from a BDR91 controlling my UFH to a HM80 which is actually better suited for the purpose.

    But there is a software hack that I have tested that works pretty well when you use the BDR91 with the UFH. Basically I wait for a Heat Demand that is > 0% but < 100% and then issue a 100% Heat Demand message instead, the BDR91 then reads that and TPI never triggers.
    It's a pity we cannot pair the BDR91 in HW mode, to a CH zone because HW does not do TPI by design.

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