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Thread: EvoHome how to have HW without CH?

  1. #1
    Automated Home Lurker
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    Feb 2020
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    Default EvoHome how to have HW without CH?

    Hi
    Having had the EvoHome for a while now and reading the very useful posts in this forum I'm still a little perplexed as to one particular issue.

    Let me explain.

    I have a S plan system to which I have two BDR91s connected - one connected to the CH valve (not the boiler fire control) and the other to the HW valve.

    Also, I have a non-EvoHome UFH circuit which I have on a separate valve with "learning" thermostat.

    I do not have the CH valve wedged open as per what seems to be the usual configuration.

    Why like this?

    Well, I have radiator valves which are not EvoHome controlled (TRVs) and I do not want them coming on when the HW is running.

    Having the boiler triggered by the valves just makes sense as that is the usual non-EvoHome way.

    The problem is that I still have the problem that I am trying to avoid i.e. the EvoHome fires the boiler for HW using the CH's BRD91 thinking it is "boiler control" as opposed to CH control and .........

    It seems like EvoHome assumes that the system is configured primarily for CH with EvoHome rad valves and then the HW valve is added on i.e. you must have boiler control and the HW addition just adds a new valve into the mix - no pun intended.

    Perhaps I should not have boiler control setup but then what fires the boiler for the CH?

    I've seen references to using a 3 * BDR91 setup and am wondering if that could help?

    FYI - the boiler I have is a system boiler with the pump integrated so I'm not sure if DBMandrake's solution is applicable or usable.

    Thanks in advance
    Mark

  2. #2
    Automated Home Ninja
    Join Date
    Mar 2017
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    Default

    You need 3 BDR91s to do what you require, or donít use one of the BDR91s as a boiler relay and use it just as a trigger for the CH MV and use the SL from the MV to fire the boiler.

  3. #3
    Automated Home Lurker
    Join Date
    Feb 2020
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    Default

    Hi
    Thanks for the reply.

    So, I am currently using the BDR91 as the trigger for the CH MV with the SL then going to the boiler as per normal S plan.

    I am very happy to add another BDR91 to the mix but what I cannot seem to find out is how this is then configured on the EvoHome.

    I presume that to start I simply use the "standard" config where the first BDR91 fires the boiler and the second then opens the HW MV.

    But if I wire the third BRD91 to open the CH MV where do I configure this on the EvoHome?

    Best regards
    Mark

    Quote Originally Posted by mtmcgavock View Post
    You need 3 BDR91s to do what you require, or don’t use one of the BDR91s as a boiler relay and use it just as a trigger for the CH MV and use the SL from the MV to fire the boiler.
    Last edited by Mlgibbons; 7th February 2020 at 07:55 PM.

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