15mm gas feed to valiant eco 428 bolier ok?

[steve121964]

IS it ok to run a 15mm gas feed approx 35ft to a valiant eco plus 428 open vent boiler?

[ambassabuild]

Im sure you will get a more detailed answer, but you will require 22mm gas feed, I may be wrong but have you the right number eco 824 not 428, let the corgi guys give you the diffinitive answer.

[steve121964]

thx for the reply anyway. Defeco 428 boiler. The only reason i ask is that it is one of the few boilers with a 15mm gas inlet feed pipe,kinda suggesting to me that a 15mm feed is sufficient, but this flies in the face of most of the comments i have read about other boiler installations.
Any advise greatly appreciated.

[heathfield]

Is any other appliance connected to the gas pipe, like a cooker? If so, with a 15mm pipe, turning on the cooker could produce a low pressure wave that travels up the pipe and results in the boiler going out. A 22m pipe will act as a gas reservoir in such a case, reducing the effect of the presure wave. Best get in a Corgi registered installer for advice on your system.

[terence7556]

this sort of question is best left to the installer, who will carry out a pipe sizing exercise, based on other appliances, if any in the property. if you have other appliances and a boiler then they may not work safely as enough gas will not reach them to work safely or efficiently
i would not consider using 15mm in my property for that length of run, w/o even considering the resistance offered by bends or fittings. there is also a possibility that you may have to start with 28mm at the meter and then reduce down to 22mm and then 15mm depending on usage in the house
this is an area where you need an experienced person to assess it, at the property.there are too many variables to provide you with a safe answer at the moment

[steve121964]

Thanks to all those who replied. Good common sense answers........much appreciated. Still curious to know why a respected brand like Vaillant would offer 15mm gas inlet and expect you to reduce downto that size when it seems that almost every other boiler manufacturer has a 22mm gas inlet as standard. Just curious but its got me wondering.....................

[terence7556]

i have an ideal classic fan flued boiler and the gas inlet pipework to the valve is 15mm, but the boiler is 11 years old.
i think that the 22mm inlet size is the norm for combi,s

[steve121964]

thx for the reply terry.
Boiler i am considering is not a combi but a new condensing unit for an open vent system.

[gucciman]

combis need a minimum of 22 mm gas supply because they burn so much gas when heating the hot water.

i cant give this as gospel without examining the installation in person but a 15mm gas supply is usually sufficient for a system boiler especially if yours is only 24kw. (it will depend on how many appliances are branched off it)

the main problem is when the householder has an old system boiler changed for a high powered combi and the installer doesn't bother changing the 15mm gas supply, happens a lot believe me.

as said before your installer can confirm for you the size of pipe needed.