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Boiler Gas Supply - 15mm or 22mm ?

Postby malctoy » Wed Mar 12, 2008 11:04 am

Hi everyone... I am considering replacing my 25 year old Glow-worm open vent heat only boiler which is currently supplied by 15mm (1/2inch).

I am interested in the Vaillant Ecotec plus 428 and one installer is saying that I need a 22mm supply up to 1metre from the boiler and then a 15mm connection. I always understood the gas pressure was the main issue and I can understand 22mm would give greater pressure.

I can't find on any site any recommendations for this and I am reluctant to proceed as major re-piping would mean major disruption to the house.

The boiler is the only gas appliance in the house.

Your advice would be greatly appreciated lads !
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Simply Build It

Postby htg engineer » Wed Mar 12, 2008 11:46 am

The installer is right - it should be a 22mm gas supply.

It's not just how many appliances connected to the gas pipe that affects the pressure. You also have to take into account the length and condition of the pipework, the number of bends and fittings etc.
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Postby malctoy » Wed Mar 12, 2008 12:02 pm

Thanks for that HTG ! Much appreciated !

The supply into the house is 22mm but to discover how far that is from the boiler would cause major disruption such as under tiled floors, carpeted floorboards etc that isn't an attractive thought !

The old Glow-worm Space Saver boiler is 15mm supply and have you any idea what the consequences would be if a new Vaillant Eco Tec 428 was connected with 15MM ?

Thanks in advance for your help !

Malc Toy
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