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Thread: Heating Partial Load

  1. #21
    Automated Home Jr Member
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    Quote Originally Posted by bruce_miranda View Post
    Viessmann doesn't play nicely with Evohome and Opentherm. Do you have OT?
    No. The Vaillant doesn't play nicely either. I've just got the BDR91 wired directly into the boiler at the moment. Apparently using the OT interface sold in the Netherlands will void the warranty on the boiler, so I am not using it

    Wouldn't it be a greater priority to have the boiler able to modulate to a very low level instead of prioritising Opentherm compatibility?

    Also this Viessmann has integrated weather control, so it will automatically modulate the flow temperature and doesn't theoretically need Opentherm if I understand things correctly
    Last edited by rs1987; Yesterday at 10:12 PM.

  2. #22
    Automated Home Legend paulockenden's Avatar
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    Why not go Intergas?

    Your landlord will love it because they tend not to go wrong, so fewer callouts.
    Your heating engineer might hate it for the very same reason though!

    Plays well with Evohome using OpenTherm.

    P.

  3. #23
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    Quote Originally Posted by paulockenden View Post
    Why not go Intergas?

    P.
    Because I'll still have the same problem and be out of pocket by a few thousand pounds. Intergas boilers all have minimum heat outputs in the 7kw - 8kw range, which is even higher than my existing Vaillant 938. It's this high minimum rating that is causing the boiler to go into anti cycle mode constantly on low heating loads, as even 6kw is too high in most cases.

    The Viessmann has the lowest minimum rating on the market, able to modulate 17:1 down to 1.9kw.

    The Viessman has very good inbuilt weather control, which obviates the need for Opentherm surely?

  4. #24
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    Quote Originally Posted by rs1987 View Post
    Because I'll still have the same problem and be out of pocket by a few thousand pounds. Intergas boilers all have minimum heat outputs in the 7kw - 8kw range, which is even higher than my existing Vaillant 938. It's this high minimum rating that is causing the boiler to go into anti cycle mode constantly on low heating loads, as even 6kw is too high in most cases.

    The Viessmann has the lowest minimum rating on the market, able to modulate 17:1 down to 1.9kw.

    The Viessman has very good inbuilt weather control, which obviates the need for Opentherm surely?


    The Intergas Xclusive and Xtreme models modulate down to ~ 3.5 kW.

    OpenTherm is a two-way comms protocol that can control many boiler functions. If you want to closely control CH flow temperature via a separate thermostat as you would with a weather compensated system, then you need a protocol like OpenTherm to do it.
    Last edited by blowlamp; Today at 12:45 AM.

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