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Discuss Hot water temperature problem in the Central Heating Forum area at

  1. fixitflav

    fixitflav Active Member

    The boiler just heats water. The hot water is a closed circuit and goes to the rads, or to a coil inside the HW cylinder, or both at the same time, depending on the system, controlled by a 3-port or 2 off 2-port valves. The coil in the HW cylinder heats the water which comes out of the taps. The cylinder stat determines when the boiler fires (and stops firing).
    The boiler manual sounds like one for a combi boiler, which provides HW direct, and has tap and rad icons to show you what it's doing. As you have a separate HW cylinder the absence of those icons is correct.
    • Agree Agree x 1
  2. chris watkins

    chris watkins Plumber Top Contributor!!

    The Tap symbol only applies if you have a combination boiler or a special probe which allows the boiler to control the cylinder but this is rarely used in this country.
  3. Chris*****

    Chris***** New Member

    Well now I understand the way it works everything becomes clearer. Many thanks for a great answer.
  4. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    It does in my humble abode lol
    • Like Like x 1
  5. YorkshireDave

    YorkshireDave Plumber Top Contributor!!

    Surly you mean on your "YorkyShiire Estate" Sir?
    We don't have humble abodes in Yorkshire - aka God's Own County!
    • Funny Funny x 1
  6. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Lol , you maybe right , when we moved in here my pal called it “ southfork “
    • Funny Funny x 1
  7. YorkshireDave

    YorkshireDave Plumber Top Contributor!!

    So, Yorkshire's version of JR? Or is it Sue Ellen?;)
    • Funny Funny x 1
    Last edited: Dec 23, 2018
  8. fronty

    fronty Member

    Any chance you can post a pic of your front panel - there are various different versions of the Vitodens 100, including a 4 pipe version that heats the hot water on a separate circuit (and doesn't need a cylinder stat).

    I have a Vitodens 100 too but it's a heat only boiler with 2 pipes, a cyclinder stat (set at 65) and 3 port valve, and no touch screen - I'm just interested in how you have yours set up as I have to run mine at near max to get decent heating and hot water. Boiler temp runs at a steady 72 degrees when it's modulating so all's good, but just feels weird having to have the temp dial on max (it's actually off the scale!).
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