Gas pipe size

Discussion in 'Plumbing and Central Heating' started by longdogs, 4 Oct 2014.

  1. hi

    just had a boiler service and gas safety check. Everything was fine and our combi is apparently 99% efficient, so all good news.

    One thing that did come up was that the gas supply pipe to the boiler (which is in the loft) is undersized. It' currently run in 22mm and should apparently be in 28mm. The run is about 8mtrs from the meter.

    My question is: Is this a requirement which has changed in recent years? We had the boiler fitted about 9 years ago, so did the installer install it incorrectly or is it just that the goal posts have moved as usual?

    Thanks
     
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  3. Dan Robinson

    Dan Robinson

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    The size would have been wrong from day one.

    Just that this chap noticed it when he did his checks. So browny points for him.


    He probably classed it as NCS if the boiler is working properly..... certainly not 99% - he needs to change a setting on his analyser ;).
     
  4. Agile

    Agile

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    Your boiler is not 99% efficient, probably about 90% if condensing or 80% if not.

    The 99% reading is a figure produced by the instrument but it is not the overall efficiency!

    Sensible of the engineer to measure the pressure loss of the gas pipe but wrong in my view to try to make you over happy by saying its 99% efficient when it is not!

    Tony
     
  5. gas112

    gas112

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    What kw size of boiler is it ? this is what determines pipe size re distance
     
  6. It's 23.3 Ideal Evo HEC22/30
     
  7. So, being totally naïve about gas, what is the problem with pipe sizing if the boiler has been working ok for about eight years? Is it not performing as well as it could be?
     
  8. picasso

    picasso

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    I cant see the pipework being under sized unless you have other appliances on the same run.
     
  9. Dan Robinson

    Dan Robinson

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    What exactly did the guy say?

    Performance could be affected. Safety COULD be affected it all depends on how undersized the pipe work is.

    The main thing to bear in mind is that when you need a new boiler (which considering what a ****box your boiler is, won't be too long), you WILL need to upgrade the pipe.

    As it stands at the moment you should be fine.
     
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  11. No other appliances on the same run
     
  12. Everything passed ok, I think it was just an observation. As for the ****box, I agree, all combis are ****boxes - bring back backboilers :LOL:

    We hope to move house next year so someone else can sort it out :LOL:
     
  13. picasso

    picasso

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    2.4m3/h on 8 meters of 22mm copper should be well within the 1mb drop even with an allowance for fittings, sometimes fitters dont take the drop across the gas valve into account.
     
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  14. Agile

    Agile

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    To a large extent in most cases it is slightly academic.

    The criteria we have to work to only allow a pressure drop of 1.0 mbar maximum.

    When it is only up to 3.0 mbar it rarely affects boiler operation although it is three times the maximum allowed.

    Copper tube is expensive and a prime example of how some will cut corners to save their installation costs.

    Tony
     
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  15. I agree. I am a plumber (not gas) and would imagine the cost of running 28mm would be horrendous
     
  16. CombustionGuy

    CombustionGuy

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    I picked a length of 28 up last week it was 14.67 in vat with a massive discount ( retail was 33.45 per 3m )
     
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