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gas hose size - bore 9.5mm or 16mm?

Discussion in 'Plumbing and Central Heating' started by TofuSpaceship, 14 Feb 2020.

  1. TofuSpaceship

    TofuSpaceship

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    Hi

    we are having a Britannia range cooker installed.
    I am getting parts for the plumber to come round tomorrow to fix it.
    On SF they sell the standard hose with bayonet fitting (as recommended by manufacturer), which has a bore size of 9.5mm.

    Isn't that too tight for a range cooker which has 12kW gas Output?

    Should I go for a semi-rigid stainless steel, yellow-sleeved gas hose which has an internal bore of 16mm? But with compression fitting?

    We are having the cooker installed finally after 5 months without kitchen (and having had a crap cooker before that), I really don't want to find that the cooker is under powered.
    Or 9.5mm is more than enough and I should go for the easy route (bayonet)?

    Your help is appreciated!
     
    Last edited: 14 Feb 2020
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  3. footprints

    footprints

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    I would worry about anyone installing a gas cooker that wants the customer to supply materials, are you sure he is Gas safe registered?
     
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  4. TofuSpaceship

    TofuSpaceship

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    I found him on the register. He lives in the neighbourhood.
    It is already the 3rd plumber that asks for us to buy parts, so I suppose it is more common than I thought?
     
    Last edited: 14 Feb 2020
  5. TofuSpaceship

    TofuSpaceship

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    My appliance is 12kW, if I divide this by the ‘calorific value’ (CV) of the gas being burnt, which is natural gas =38.5MJ/m3.
    12/38.5=0.32 flow rate expressed in litres/sec, which equates 1.13 m3/hour.

    Now I just need to understand if the 9.5mm bore is enough?
    Can someone please advise?

    We have been living in squalor for five months, we are quite close to the end and I love for things to be done simply in the right way
     
  6. footprints

    footprints

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    OK if he is registered. I was a Corgi installer and would never get customers to supply, you have no idea where they sourced it (ebay) I used reliable suppliers so that way I was confident the stuff I was using was good quality.
    I would expect a standard Cooker hose to be fine, in fact if you saw the injectors for gas burners they are tiny often less than a mm in dia, in round figures a 9mm hose would have a cross section of more than 60 sq mm. (If I have my π r2 formula right :)) If still worried just give your installer a ring.(y)
     
  7. TofuSpaceship

    TofuSpaceship

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    I agree, I would think a CORGI who takes responsibility to sign things off on his/her own name, he/she would definitely want to know that the parts he/she is using are good qual.
    To be fair, in the past I supplied for plumbers doing pipeworks the cheapest SF fittings and pipework and had to return it all back because they wanted all HEP2O.

    I am sourcing them from SF anyway, so no cheapo stuff, as I stated I really want things to be done simply good, and I am not one to skimp on things to save me 10% of cash and have +50% more troubles.

    Thank you for your help @footprints , really much appreciated.
    I was going on a tangent trying to calculate the pressure drop and all that, I found a document which helps in that regard, but states that for copper size of 10mm x 0.6 (I assume 0.6 is the thickness of the pipe wall), the max flow that a 3m run can provide is 0.84 m3/hr.
    Now, the hose would be half the size, but looking at the progression of supported m3/hr for every 3m increase, I fear a hose of 9.5mm bore size is not enough?

    [​IMG]

    Taking on on your approach instead Footprints:
    I have the manual of the cooker under my eyes. I read the "NAT GAS INJECTOR" for every burner of the cooker has numbers like 97, 117, 130 and 150.
    Would these be equivalent to sizing in mm, i.e. 0.97mm, 1.17mm etc.?
    I calculated the 9.5 bore hose to have 70 sq. mm. section, so your formula is pretty bang on!

    Thank you again
     
    Last edited: 14 Feb 2020
  8. TofuSpaceship

    TofuSpaceship

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    I am perhaps over-complicating this.
    Reading the manufacturer instructions for the hose with the bigger bore size, it is not OK to be installed with free-standing cookers. :mad:

    Well.
    9.5 will it be then.

    Still would be great to have your guesses on what are the numbers next to the injectors type in the cooker manual referring to.
     
    Last edited: 14 Feb 2020
  9. footprints

    footprints

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    Jets are sized using a numbering system one of those weird sizings may have been based on thous of an inch in the old days. Engineers are a law unto themselves why else would a 2BA spanner be bigger than a 4BA!
    As I said don't stress about it if you are worried ring your installer he will not mind he wants to turn up and have the right bits as much as you.;)
     
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  11. durhamplumber

    durhamplumber

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    Very very weird ....Especially when they can make more money buying their own parts
     
  12. durhamplumber

    durhamplumber

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    How long is the run?..What diameter are the pipes?
     
  13. durhamplumber

    durhamplumber

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    No such thing anymore
     
  14. TofuSpaceship

    TofuSpaceship

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    the run from the tee (feed to the T is 28mm pipe over a run of 20m effective length) is probably 3 or 4m of effective length in 15mm copper pipe
    Then it would be connected to cooker with 1/2 inch hose which SF claims it has 9.5mm bore size; length of hose is 1m
     
    Last edited: 14 Feb 2020
  15. TofuSpaceship

    TofuSpaceship

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    it does beg the doubt. However in my case, I can see why they have done it: bought parts from SF for a certain amount, plus the quote for gasman to do all the gas work and boiler (labour only), the total was a decent sum, not too large not too small. As we know and trust the man, not worth the hassle shopping round.
    After the first day of work, turns out many more parts are needed, bringing the original material bill to 3 times as much.

    Having had the actual final total that we spent from the gasman directly as a quote of labour + parts, we probably would have shopped round.
     
  16. durhamplumber

    durhamplumber

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    Is this at the gas meter?
     
  17. durhamplumber

    durhamplumber

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    Freekin jeezez .......you are only having a cooker installed..WTFff goes on...Is this a wind up?..Mr Wobbe number!
     
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