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Reverse boiler flush? (Viessmann Vitodens 100)

Discussion in 'Plumbing and Central Heating' started by MikeAustin, 20 Dec 2015.

  1. MikeAustin

    MikeAustin

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    Was initially 3, to match the one it replaced a few weeks ago. Now it is on maximum.
     
  2. Cgas

    Cgas

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    Obviously don't know size etc of your system but try knocking pump to 2. Had a similar problem on a glowworm cutting off at 52deg and showing f22 I think it was...ignition temp too slow or something along them lines. Glowworm pushed for either new pump or heat ex, pump was fine but running at 3 so knocked down to 2 and never heard back so gather it worked, was about 6 months ago.
     
  3. MikeAustin

    MikeAustin

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    This did not make a lot of sense to me but, as it was easy to check, I tried it anyway. Max temperature was reduced from about 60C to 56C. So I returned the pump to max.
     
  4. simond

    simond

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    Get that filter opened up.
     
  5. MikeAustin

    MikeAustin

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    What filter do you mean? That last picture was the old system. It was all removed in 2005 when the Viessmann was installed. My Magnaclean has been checked with every flush.
     
  6. Agile

    Agile

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    My experience is that virtually all blockages have been at restrictions, namely connections onto boiler HE, pump valves and motor valves etc.

    Also I have found sulphonic acid [ DS3 ] will often dissolve blockages not treated by citric acid.

    Tony
     
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  7. MikeAustin

    MikeAustin

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    Thanks Tony. I presume you use DS3 on components separately and DS40 for a running system? Have you found it effective when used without a powerflush?
     
  8. Agile

    Agile

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    No, I use DS3 in the system water.

    But it is not very soluble and needs to be at about 60 C to start to dissolve much at all.

    It all depends on what the blockage is and citric acid is suitable for most pure metal oxides but the DS3 is better when there is calcium present which is often the case when deposited in a boiler HE.

    Of course HCl is very good but forms corrosive compounds with copper which attacks steel radiators very well.

    HCl is fine used carefully on removed parts.

    A power flush is primarily for when there is a lot of dirt inside the rads. And it does not dissolve the rads unless you have added any acids to it.

    Tony
     
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  10. MikeAustin

    MikeAustin

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    Oh dear - not much good if my boiler is struggling to reach 60C !
     
  11. Agile

    Agile

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    Mike, how sure are you that the boiler heat exchanger is clear of air?

    As you know the HE is a horizontal spiral of stainless coil. So if the upper parts contain air this will reduce the area of water in contact with the metal.

    With the combi and system boilers there is a procedure to be done on installation using the valves underneath.

    On yours as its an OV boiler getting the air out of the top connectors is not so easy. You need to find a way of forcing water through it very fast and this is normally done using mains water to drive the air out.

    I was wondering if the air disasters TV program is must see for you or too close to work to interest you? Its my favourite one.

    If you get stuck then you could always call me on my mobile number.

    Tony
     
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  12. MikeAustin

    MikeAustin

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    It is a good point, but I have mains flushed it six times, so I hope that forces out air every time. I was not able to find how to bleed this boiler in the installation and service manual anyway.

    I watch it sometimes - it keeps me on my toes.

    That's a very kind offer. I will bear it in mind.
     
  13. Agile

    Agile

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    It is not just flushing in the sense of making the water move.

    But it needs a very good fast flow of perhaps 15 litres per minute plus to drive any air forward.

    Tony
     
  14. MikeAustin

    MikeAustin

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    There is no mention of clearing air from the heat exchanger in either the installation instructions, service instructions or fault finding. Nor is there any mention of filling the HE. Are you familiar with the Viessmann 100c and clearing/filling its HE? Or does anyone else know?
     
  15. MikeAustin

    MikeAustin

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    I am wondering if something has gone amiss with the PCB, so here is an outrageous suggestion.
    If my boiler is OK with HW but not with CH, it does not necessarily mean the boiler us OK, end of story. It only means it is OK with HW. Could I somehow swap the electrical connections round so the boiler thinks the CH is HW and vice versa? It would prove whether the PCB is OK.
    Is there something I am missing, apart from being a sandwich short of a picnic?
     
  16. 45yearsagasman

    45yearsagasman

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    I had an idea, but reading this thread it seems you've not followed much advice given by the professionals.
     
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