Nearly all manufacturers instructions require you to fit 22mm. gas supply to the boiler. These take preference
and so back to my original point that if you replace a 28kw combi with another 28kw combi there's a fair chance it will be fine, especially bearing in mind that the input will actually be lower on the new one.
it may be stupid tony but thats what WB GW and vaillant say
I'm not trying to do things cheaper
I will bet anything that you choose the lowest quoted price safe in the knowledge that any undersized gas supply will have to be upgraded at the (huge) expense of the installer when you complain to Corgi.
I cannot agree with that statement!
Almost all boilers fitted 10 years ago had undersized gas supply pipes.
Its stupid for a manufacturer to say that you need a 22 mm supply pipe without knowing the effective length!
If you have no more than a 1mbar drop from the meter in working pressure at your shiny new boiler then it does not matter what the size of the pipe is. It is true that quite often 22mm pipe is required to obtain this, but in my experience if you have a 28kw combi with the correct working pressure and replace it with another 28kw combi there's a reasonable chance it will be fine.
The diameter of the pipework (7) is 15 mm. Connect a
gas supply pipe of not less than 15 mm diameter to the
copper tail.
Note
Ensure the gas supply pipework is adequately
sized so that a 20 mbar gas pressure is available
at the boiler inlet at full flow rate.
I'm not trying to do things cheaper
Of course you are.
You have already decided what unrealistic price you want to pay without knowing any of the issues.
I will bet anything that you choose the lowest quoted price safe in the knowledge that any undersized gas supply will have to be upgraded at the (huge) expense of the installer when you complain to Corgi.
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