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Discuss 15mm vs 22mm gas pipework for new boiler. in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Len

Currently have a very old open system gas boiler which services the hot water system, via a storage cylinder and a ring of 11 radiators.

Needs to be replaced and I have selected the registered installer to carry out the work. Others who quoted for the work mentioned that the gas feed would have to be upgraded to 22mm (based upon the visual inspection of 1.6m of 15mm pipe rising from the floor to the current boiler). Only one asked about the current pipe work feeding to this 15mm length.

The proposed condensing boiler to be installed is the Vaillant Ecoplus 618 which has an inlet gas pressure requirement of 20mbar on a 15mm connection.

The position of the new boiler is up in the loft which will require a 6mtr extension to the current gas pipe.

The feed from the street to the gas meter is 28mm steel reducing to 22mm copper and the outlet from the meter is 22mm copper back to 28mm steel that then goes under the floor (solid) across to the garage and then is fed up to a T in the floor below the boiler - a length of 4.3m. The T splits the gas to the 15mm for the boiler and then goes under the floorboards to feed a supply to the cooker which is not used.

My neighbour had his boiler moved to the loft about 2 years ago and the installer used 15mm pipe all the way.

Have read numerous feeds about 15mm vs. 22mm and the Corgi changes to the regulations and have got confused..

Will be seeing the installer shortly but need to understand what are the requirements for gas pipe and will I end up lifting the floorboards in the kitchen to allow the installer access to the T to change the pipe diameter.

I do not know the gas pressure into the house – but surely the size of the gas inlet pipe should be enough to feed the required mbar pressure required by the boiler?

Thank you reading this far and any guidance you can offer.

Regards
 
You'll need 22mm from the 28mm [1"] steel to the boiler, the important thing is there should be a max of 1mbar working pressure drop at the boiler [on all appliances ] from the meter working pressure. If more than 1mb the whole installation will need upsizing, but all should be ok with your installation.
The GS engineeer will know this.
 
is it a combi, do you know the output in kw? i almost always use 22mm becuase it needs that much gas!
 
The Vaillant 618 I will be purchasing is not a combi just a sealed condensing system boiler with a maximum output of 18Kwh.

It is smaller than my Neighbours Potterton (in kwh) but will be in the same position in the loft and have the same length of pipe runs - both gas, hw and ch. We both have power showers. I could not find a combi that would meet the demand plus all the other bits you would find in a house of 4 adults.
 
im not sure why you couldnt find a combi to satisfy your system? not that it matters, the 18kw is what matters. thats still quite an output for a domestic boiler, prob is , if they fit 15mm and check the gas rate and its down, its another job, id fit 22mm
 
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