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Thread: Help!! Need advice re switching Evomhome from BDR91 to OpenTherm boiler control

  1. #11
    Automated Home Ninja Dan_Robinson's Avatar
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    Had fun working on these a year or so ago:

    20131217_105459.jpg

    20131118_131717.jpg

    Total blast from the past. Think they've been British Gassed by now though
    Last edited by Dan_Robinson; 24th January 2018 at 08:53 PM.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  2. #12
    Automated Home Lurker
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    Thanks very much for all the replies....

    So to summarise, any zone with an actuator / hr92 doesnít need a zone vale too, hence the engineer suggesting getting rid of those and putting in a 2-port purely for the hot water.

    What purpose does the bypass serve ? I ask as itís entirely likely that I could put TRVs on them so Iím keen to understand how that changes things.

    From a wiring perspective, presumably the CH bdr91 comes out completely and the switched live to boiler removed in favour of the OT connection ?

    Thanks again for the help.

  3. #13
    Automated Home Ninja Dan_Robinson's Avatar
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    Bypass is there to maintain a minimum flow rate through the boiler as circuits close down.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

  4. #14
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    Dan,

    Thanks for the explanation. So It sounds like a pretty reasonable recommendatio in that case.

    Presumably with the removal of the Valves on the CH loop that water just continually flows governed by the pump speed and heats / not radiators or UFH based on the HR92 or actuator setting, is that right ?

    Also I am considering changing to an unvented cylinder with a larget capacity, does this plan have any impact on that..or would there be any better ways to do it with that in mind ?

    Thanks again.

    Rob

  5. #15
    Automated Home Ninja Dan_Robinson's Avatar
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    Water will only circulate if there is somewhere for it to go. If all the valves are shut down, the the system will be off. If one rad opens, then water will flow to that valve and any "bypasses" in the system.

    Going unvented should materially affect anything, but save the immersion probe that comes with the hot water kit.

    Joule cylinders are our preferred option. Megaflow are over priced for what they are, however, they do have a dedicated place for the immersion probe to go. I just push it through the hole in the Joule Aquastat however.
    Kind Regards - Dan Robinson (Jennings Heating Ltd)

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