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Glow Worm 30sxi - Noisy Ignition

Discussion in 'Plumbing and Central Heating' started by evilweasel, 9 Sep 2011.

  1. evilweasel

    evilweasel

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    Hi Folks

    First post - I've searched to see if this one's already been covered, but can't find anything, so here goes...

    I have a 5yo 30sxi boiler that provides CH and HW via a megaflo cylinder. All has been well for the last few years or so, but recently I suffered from the burner gasket breakdown issue, which killed the internal expansion tank. I replaced the tank, and the gasket (the burner cover had slightly warped but a good tighten on the flange nuts closed it off), and all has been well for 10 months or so.
    Now the latest issue is this - on ignition, there's a distinct 'flutter' or shudder even, that can be heard all through the house. I have read that a poor mixture can cause dodgy ignition, so I've just opened the covers and checked the fan, and gas valve voltages. The manual states that both should be at 24v. The valve is at 13v and the fan at 30v. Methinks that something is amiss, as I thought gas pressure was modulated by fan speed so I'd expect both these values to be within limits. My understanding was that on demand, both levels should be 24v and fan speed was controlled through the additional wires on the fan connector.

    Has anyone else had experience of this?

    Could it be the gasket failing again, causing the poor mixture?

    Could the fan and valve voltages point to another issue, or are they normal?

    Am I completely off the mark?

    Many thanks

    John
     
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  3. Beerlover

    Beerlover

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    Get a new burner door and a RGI - you are dangerous, hope the boiler isn't.
     
  4. evilweasel

    evilweasel

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    Thanks for that - but I think 'dangerous' is a bit strong... I have no problem in employing the services of a RGI but firstly, I'd like to be well informed on what's wrong, and secondly have at least explored the possibility of repairing an issue myself.

    The burner door really was just very slightly warped - and sealed perfectly in the end. There's no evidence of condensate in the inner casing of the boiler, so I'm pretty sure it's still sealed.

    I wonder if anyone could comment on the fan and valve voltages, as they appear to be out of spec?

    Many thanks
     
  5. Youllneverguess

    Youllneverguess

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    Well is must be fine then :!: :eek:
     
  6. evilweasel

    evilweasel

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    Sorry - let me clarify... By 'no evidence of condensate' I mean there's no condensation in the inner casing - which as far as I can tell means that the burner door seal is good.

    Apart from one rather blunt and another condescending reply I've got no useful information at all so far regards what the root cause of the issue may be. I hope that someone can perhaps make a more constructive response than the ones so far.

    Here's hoping

    [/b]
     
  7. monoxide62

    monoxide62

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    What does the FGA say?
     
  8. evilweasel

    evilweasel

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    Thanks!

    Unfortunately I don't have one, so don't know. Based on what I've read, I saw that one possibilty behind the 'flutter' on firing was poor mix. Then I checked the fan and GV voltages, and they looked out of spec. For all I know the combustion could be spot on - and the fault is something else entirely.

    Do you know if the fan and GV voltages should vary?

    Sorry I haven't got any more info for you.
     
  9. 45yearsagasman

    45yearsagasman

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    EW, no responsible member on here will give you advice on the faults and how to repair your boiler.
    You neither have the test equipment or the knowledge to ensure your boiler is safe to operate.
     
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  11. transam

    transam

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    Its a wind up!!! IMO ;)
     
  12. evilweasel

    evilweasel

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    Not a wind up, just an engineer (albeit from a different discipline) looking to understand the root cause of a problem with the aim of being better able to make an informed decision on how to proceed.

    It seems pretty clear now that the level of advice available on this part of the forum is directly proportional to the regard in which the OP's abilities or knowledge is held, and I appear to have reached my level....

    All I'm trying to do is find out what the possible causes of my issue are - and so far, I've done some research that would point me in the direction of combustion mix, and have also discovered some voltages that appear out of spec.

    I'm not naive enough to expect chapter and verse on exactly how to pull my boiler apart and replace bits, left right and centre, just looking for advice on what might be the likely causes.

    And I'm still really interested to know if 13v on the GV and 30v on the fan is normal.

    Cheers
     
  13. Youllneverguess

    Youllneverguess

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    Only the manufacturer can tell you if the voltage deviation you have is in or out of spec and this info is not likely to be common knowledge.

    Unless you have an FGA all your tinkering is nothing more than dangerous. You being an engineer has little to do with it.

    You have pretty much ascertained the possible courses. Be happy with that.
     
  14. Agile

    Agile

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    Its difficult for me to guess at what kind of engineer you could be when you dont seem to appreciate that the combustion conditions of a boiler are measured with a flue gas analyser and not a voltmeter!

    The forum rules which you are deemed to have read before posting here clearly say that........

    Tony
     
  15. evilweasel

    evilweasel

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    Thanks to those who gave the helpful and informed comments - let's be clear, I'm going to employ the services of a RGI, based on your advice. I don't have the tools or qualifications to effect a repair myself.

    But - generally speaking - it would have been nicer to have had that advice without all the negative stuff that came along with it.

    Unfortunately, the domestic plumbing and heating industry has occasionally been marred by a minority of traders taking advantage of customers by overcharging for minor repairs, or by carrying out unnecessary work. In truth, my motivation is to mitigate the small possibility of that happening, by understanding exactly what the required service intervention might be. I hope now that I'm better equipped to do just that.

    And to the last post - you're clearly a well respected and prolific contributor to this community and I would not even think to call into question your expertise or experience - but please..... I just wanted to know if the problem was electrical or not, and stated some voltages that might assist in diagnosing the issue. I really do know that all that carbon, hydrogen and o2 burning up is of course going to need something more complex than a DVM to analyse combustion efficiency.

    I'll leave you to keep guessing as to what kind of engineer I am though, and in future I'll make sure to keep an eye on the forum rules too - just like everyone else!
     
  16. Youllneverguess

    Youllneverguess

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    Tantalised, we are not. How many DIY'ers do you think come on here saying "I'm an engineer in [insert some unrelated field of your choosing] so I know enough to play with things I haven't got the experience or equipment to test reliably." over the course of a year?

    If you get an RGI, then all you have done is succeeded in getting enough information to annoy the a*se off him by looking over his shoulder and asking questions whilst he is trying to work things out in his own way.

    As you say the unscrupulous ones are in the minority!
     
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  17. transam

    transam

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    so to sum it up ? u do not trust who ever u are going to engage to look at your boiler ? as they are likely in your opinion to rip u off ? maybe ?

    Have u never had your boiler serviced ?
     
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