Current gas boiler has 15cm feed

Mankysteve

John_the_Boy wrote: »

In the end I had a pipe up the side of the house through the loft and down the back to the boiler. British Gas (expensive I know) include this as part of the price but I was quoted approx £600 - £1000 by a local gas fitter so in the end it was only a little dearer to go with British Gas.
Have to say they did a reasonable job in the end.

My parents had a new boiler installed by BG last year and yes while it was more expensive they where very happy with the job they did bar one thing they installed an RCD for the boiler in a odd spot at the top of the stairs, but i suspect that it was because of the boiler being in the bathroom the isolation switch need to be in easy reach.

keystone

ukjoel wrote: »

..........you dont need to upgrade from 15mm to 22mm unless there are issues with [STRIKE]water[/STRIKE] gas pressure. Also its possible that just replacing a portion of the pipework will often lift the pressure so its doesnt all need to be done.............

and

Firstly check if the gas pressure can be increased at the mains - if you only have a small amount of thin pipe it might just be ok, the larger the boiler the less chance this option will work.

No its NOT a pressure issue. The pressure at the end of 10m of 15mm pipe will be the same as the pressure at the end of 10m of 22mm pipe when fed from the same source.

Its all to do with flow rate which will be higher through the 22mm.

Cheers

gas4you

All gas appliances, in this case a boiler, burn a spefic amount of gas when on full power. In the case of a 30Kw combi for instance, this is approx 3m3/hr.

The gas pipe work has to be sized to give this flow rate and only a 1mbar drop in pressure across the pipe carcass from the meter to the appliance.

Increasing the working pressure at the meter will not overcome the problem if the pipe size is too small to carry the correct amount of gas with the 1mbar drop needed.

The greater friction that the smaller pipework will create, gives a secondary effect of reducing the inlet pressure to the appliance when it is on full.

Other gas appliances that use the same gas carcass also need to be taken into consideration.