Next GlowWorm 30CXi problem...

Discussion in 'Plumbers' Talk' started by Fada Mach, Nov 12, 2010.

  1. Fada Mach

    Fada Mach New Member

    Ok, it's basically running fine, but will go cold for a few seconds when drawing hot water - such as when in the shower...

    I've listened to what the boiler itself has to say about this, and what it does is to 'cycle' over a period of around 20 seconds. Ie: when the hot tap is on and the boiler has fired up, instead of the fan 'burning' at a steady rate to suit the water demand, it fires up high and then slowly slows down before slowly speeding up again. The time between two 'lows' is around 20 seconds. Sometimes the actual burner will shut off completely for a few seconds when it's a min speed - hence the chilly water - before firing up again.

    So, with DHW demand, should the fan/burner be at a fairly steady speed to match the demand (modulate like it does with the CH)? Or, is it normal for it to cycle like this?

    And why is it doing it? Water flow itself is fine, and inlet filter checked when I did the filling tap - clean as a whistle.

    Any ideas?

    Ta very much.

    (And even tho' installed it myself, I won't be going anywhere near internal gassy bits. I just like to 'understand' :))
  2. chris roast

    chris roast Member

    replace plate heat exchanger
  3. vokey

    vokey New Member

    Is the system clean ? i.e partially blocked plate heat exchanger,
  4. chris roast

    chris roast Member

    you could take of plate heat exchanger and flushed, but sometimes easier to replace with new,
  5. tomplum

    tomplum Active Member

    fada, (phew it took ages to post this, this site is slower than a post office queue), go to toms tips, flushing a system, do it my way, then run x400 throught the system for a few days, then flush my way again, add x100 and let us all know the results,
    this is a no bull, no gimmick method and if it dont work this whole site will know, and if it does work, and you don't hear from me . the powerflush manufactures have hit me
  6. Fada Mach

    Fada Mach New Member

    Kuuurrrryyyyssssst, Tom, you're right - slow beejeeessuussss.

    When I fitted the boiler I did flush the system pretty much as you show on yer tube; added x400 for a few weeks, removed all rads and flushed them through in t'garden and then connected a hose to one end of the circuit and ran it through for ages. Samples from the CH water show clear.

    However, the consensus above suggest it is the exchanger.

    I shall investigate how easy it is to remove the exchanger for a looksee and clean.

    (PS, Tom, I notice some **cough** twit called forpity'ssakes *cough cough* made some disparaging comments 'bout your geeeetar. And you didn't bite. Damn...)
  7. tomplum

    tomplum Active Member

    where is this remark ? point me
  8. Fada Mach

    Fada Mach New Member

    Eh? You must have started on yer 58 pints early...

    "toms top tips, how to flush a central heating system
  9. tomplum

    tomplum Active Member

    right ok get it now fada, i'm not unwindable, just a bit slow at times, but not as slow as this site, i did't click till i saw your utube account,
    maby you should before changing heat ex try the thermister, its only about a tenner, too many folks think , sludge and we're all doomed, its promoted by powerflush makers,(bit like religion) oh oh i opened a can o worms here,:)
  10. Captain Leaky

    Captain Leaky New Member

    Well I do agree with you about the powerflushing nonsense Tom Spot on birthday boy! DA, the thermister is worth a try.....unreliable combi's eh? ;)
  11. Fada Mach

    Fada Mach New Member

    Pah. I think it's done pretty well so far...!:)
  12. Captain Leaky

    Captain Leaky New Member

    It will be all downhill from now on ;)
  13. Fada Mach

    Fada Mach New Member

    No it won't - you ain't getting anywhere near it.
  14. So, is the DHW Thermistor the same as the 'Flow Switch Sensor' Part 2000801910?  Can this item be tested? A particualr resistance at a certain temp, for instance?

    Ta much.

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