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Type: Posts; User: Johntheo

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  1. Replies
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    Its the boiler return temperature that determines...

    Its the boiler return temperature that determines the boiler efficiency and has to be down to ~ 55C before any condensing effect, 55C gives ~ 86%, 48C gives 90%, 40C gives 95% & 25c ~ 98.5% so if the...
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    Once the HW supply temperature falls to the mixed...

    Once the HW supply temperature falls to the mixed flow temperature then the UFH pump will be supplied only from here, it will pump it through the UFH loops and return it all to the boiler so boiler...
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    Thanks, understood, but the TMV will demand full...

    Thanks, understood, but the TMV will demand full flow from the boiler circuit and none from the UFH recirc due to the mixed temperature reduction so probably requires boiler circ pump running as well...
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    Is this how it works?. During the off cycles, the...

    Is this how it works?. During the off cycles, the boiler circ pump & the UFH manifold pump are running (with the UFH zone valve open).
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    Yes, of course. If I had Evohome installed...

    Yes, of course.

    If I had Evohome installed and had a spare HR92 laying around I would set it very high to get the boiler to fire continuously (assuming prolonged heating demand > boiler min...
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    But, once the target temps are all met then...

    But, once the target temps are all met then Evohome will still cycle the boiler even though the minimum heating demand may be well above the boiler minimum output.
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    Yes, but even if you have a boiler with a very...

    Yes, but even if you have a boiler with a very low minimum output, my understanding/query? is that the Evohome will still cycle it when all room temperatures are satisfied even when the boiler would...
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    If I'm interpreting how Evohome works then even...

    If I'm interpreting how Evohome works then even if the heating demand is > the minimum boiler output, it will keep cycling the boiler if all the rooms are within one deg of their setpoints?, it would...
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    So, if not overshooting the set temp then running...

    So, if not overshooting the set temp then running continuously, or at least longer before cut out??.
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    Think you can get a Viessmann vitodens 200?? that...

    Think you can get a Viessmann vitodens 200?? that will modulate right down to something like 1.9kw and is still capable of something like 36kw max output.
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    Agreed, but my reason(s) are still valid, the...

    Agreed, but my reason(s) are still valid, the minimum output of your boiler is 9kw, quite high, and its quite probable that your heating demand is less than this very frequently so flow temp...
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    Maybe the boiler is just bordering on shutdown if...

    Maybe the boiler is just bordering on shutdown if its minimum output is = or > the heating demand, boiler shutdown occurs on most gas boilers at flow temp SP+5C (to 8C). Obviously if the heating...
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    If you are replying to my post, then a room temp...

    If you are replying to my post, then a room temp of 20C with flow/return temps of 60C/40C, the rads will emit 51.5% of their rated output and if the room temp is/was 15C will emit 62.9% of their...
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    What is your measured return temperature with a...

    What is your measured return temperature with a measured flow temperature of 60C.
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