Gas pipe sizing

Discussion in 'Plumbers' Talk' started by wwwdot, Jun 24, 2008.

  1. wwwdot

    wwwdot New Member

    Arranged for a gas fitter to install a combi in my son's flat. Boiler (Vokera Compact 29he) has been fitted but he has to come back to fit the flue as his ladders wouldn't reach the roof, hence gas supply has not been connected. The gas meter is about 40 ft away and piped up in 22mm running in the loft space. A living flame fire is taken off before the boiler. The fitter has taken a 15mm pipe off the 22mm in the loft and run approx 16ft including 8 90 degree bends up to the boiler.
    The feed for the hob is taken off this as well.

    Surely the boiler supply is undersized ?

    comments please

    wwwdot
     
  2. t26

    t26 New Member

    yes pipe should be 22mm to boiler
     
  3. Joelp1

    Joelp1 New Member

    22 might be undersized too over that distance/bends
     
    exbg likes this.
  4. t26

    t26 New Member

    gas engineer should be able to work out the size and suitability of all pipework
     
  5. Brid

    Brid New Member

    He will have to fill out the benchmark logbook when he commissions the appliance. It will show the gas rating (how many m3/h of gas the appliance burns) He may just copy this from the M,I's! See if he gets his stop watch out while he is at the meter while the hot water tap turned is on.
    Ask him what the working pressure of the installation is (19-23 mb). What ever the figure is, it should not be any more than 1mb less at the appliance inlet.
    You may then wish to get another gas engineer to check it after he as gone. This may save you getting egg on your face if he is correct and you are trying to tell him his job. On the other hand any money he has saved on any undersized pipework, he will have to put right, probably free of charge!
    Make sure he registers the Installation with Building control or through CORGI (he may charge you an extra fiver for that)
     
  6. wwwdot

    wwwdot New Member

    Thanks for that guys, I get a few boilers installed for people and my regular RGI always uses 22mm up to within 6" of the boiler gascock then 15mm This one is in London so have had to get someone locally. I think he is just trying to save a few bob on materials. I Will ask him direct before he fits the flue if he thinks its ok and gauge his reaction. To be honest not to impressed with his craftman ship either
     
  7. graceland

    graceland Active Member

    you could try ringing boiler manufacturer to confirm your doubts
     
  8. billybongos

    billybongos New Member

    I fitted a vaillant 37kw with the gas pipe 66ft / 20m away.

    did it ALL in 28mm pipework, (future proofing for gas cooker and gas fire). did all the gas pipe sizings extremely precisely.

    wondered why my drop to the boiler was ZEROmb
     
  9. Dick Puller

    Dick Puller New Member

    It may be OK with a 'zero' gas valve on a 'Band A' boiler.
    However, most need to be spot on dynamic pressure wise. But you are paying him as a Corgy/Capita RGI, if he's got it wrong then he's got to fix it.

    A lot of times we just fit 15mm to a combi, if it's on the low side, we just get Gas Network to change the meter regulator & bung their fitter a score for his trouble. Money always makes the paper work right, know what I'm saying son!!! Around here there's gas network guys that'll do you an illegal gas connection for £200, no questions asked, oh & never a gas bill either......LOL!!!
     
  10. wwwdot

    wwwdot New Member

    Hi Dick,

    Band B boiler, thanks for the info. He seems to have gone all round the houses to pipe it up hence the 8 elbows. His Father gave me the quote but the son did the work. I don't think its right but I'm not an RGI
     
  11. Water Systems

    Water Systems New Member

  12. Belfastboy

    Belfastboy New Member

    Here is the usual classic call to a warranty engineer. "My hot water is poor and the boiler runs all the time but the radiator don't get very hot."

    Let him install it, as him to put the gauge on the inlet test point and run the fire and boiler at high fire, the minium pressure at teh boiler inlet should be 20 mb but the compact can operate ok down to 18 before you start to affect the the burner pressure.

    Sound like he need a refresher course in pipe sizing.

    Question, did he leave it connect to the gas service without the flue attached??
     
  13. aphs

    aphs New Member

    I fitted a vaillant 37kw with the gas pipe 66ft / 20m
    away.

    did it ALL in 28mm pipework, (future proofing for gas
    cooker and gas fire). did all the gas pipe sizings
    extremely precisely.

    wondered why my drop to the boiler was ZEROmb

    So you fired a 37Kw boiler at full rate off 20 meters of 28mm gas pipe and had 0mbar drop across it. Utter ******.
     
  14. aphs

    aphs New Member


    A lot of times we just fit 15mm to a combi, if it's
    on the low side, we just get Gas Network to change
    the meter regulator & bung their fitter a score for
    his trouble.

    15mm gas pipe to a combi, Jesus wept, bet yer still using hairfelt lagging aswell. And after changing the governor that 5 mbar drop will still be? You guessed it a 5 mbar drop.
     
  15. aphs

    aphs New Member

    Had a woman phone me to query why I had to upgrade the gas pipe on a quote I gave her a few months ago. The existing boiler is in the loft roughly 25 meters from the gas meter existing supply is 22mm she wanted a 37CDi fitted in the same position but doesn't want gas upgraded due to the hassle. Can't fit it without upgrading the pipe says me, none of the other quotes I have received want to upgrade the gas pipe says she, and I have one from BG. I can't help they aint doing there job properly says me.

    Result some cowboy will have it running off the 22mm supply by now with 9mm lagging on the flow & return if she's lucky.
     
  16. billybongos

    billybongos New Member

    So you fired a 37Kw boiler at full rate off 20 meters of 28mm gas pipe and had 0mbar drop across it. *.


    Oh really?

    £10,000 says I'm right. Are you sure you can match that amount of money?

    I don't think so. why not message me, and come and see for yourself, SON!

    [Edited by: admin7]
     
  17. billybongos

    billybongos New Member

    aphs

    Everyone is wrong sometime or other. Unfortunately, its you this time... I wonder if you'd me man enough to admit it, or take up my challenge ;)
     
  18. tackleburger

    tackleburger New Member

    Did the guy arrive on a stage coach. Sounds like a chancer I'd be concerned about this and get it checked.
     
  19. doitall

    doitall New Member

    ******.


    Well aphs it's like this

    20m of pipe plus say 10 bends =25m.

    Now the bad news is 25m of 28mm pipe will deliver 5.4m³/h, now for the tricky part, 37kw converted to m³/h = 3.46m³/h.

    Conclusion buddy is 28mm will eat it.
     
  20. doitall

    doitall New Member

    wwwdot.

    Yes the pipe is very much undersized.

    The boiler is 2.7m³/h, fire say 0.8m³/h, cooker hod 0.7m³/h ish.

    So you need 28mm to the first branch, and possibly the second, then 22mm to with 1m of the boiler.
     

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