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Viessmann Vitodens 100 Combi Issue

Discussion in 'Plumbing and Central Heating' started by It Don't Work, 14 Jan 2016.

  1. It Don't Work

    It Don't Work

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    I have a 4 year old Viessmann Vitodens 100 Combi boiler feeding an unvented hot water system and underfloor heating system.

    My issue is with the hot water circuit.

    When the hot water system switches on in the morning and the boiler fires up there is distinct rattle/judder which lasts a second or so and seems to come from somewhere between the boiler outflow and the motorised zone valve (Honeywell 4043 2-port). This occurs again with the first significant use of hot water (shower/bath) but will not occur again until the next on cycle (mid afternoon).

    The piping is secure at the boiler end and cylinder end, although I guess there could be a loose clip somewhere in the pipe run.

    Any thoughts? I was wondering if there might be some sort of pressure issue or perhaps a sticking valve resulting in a sudden surge of water in the circuit. Or could the coil inside the hot water cylinder be loose (Santon Premier Plus)?

    I am not a plumber!
     
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  3. muggles

    muggles

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    When was your cylinder last serviced? It should be done annually, as per the manufacturers' instructions. I suspect that the sound you're hearing is water dumping out of the pressure relief valve as the cylinder heats up
     
  4. It Don't Work

    It Don't Work

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    System was serviced a few weeks ago. No sign of water weeping from the drain. My mind keeps turning to a sticking zone valve at the cylinder end or perhaps a dodgy flow limiter at the boiler end.
     
  5. Agile

    Agile

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    You don't have a combi boiler!

    Why not call whoever serviced it if they can do repairs?

    Tony
     
  6. It Don't Work

    It Don't Work

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    You are right. It is not a combi (just looked and the correct reference is, I think, 100-W System). My engineer has looked into the problem and can't identify the source of the rattle/judder.
     
  7. Agile

    Agile

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    Is he deaf or just does not know how to find it?

    Tony
     
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