DO I need to increase my 22mm gas inlet pipe

[tehranman]

I'm new to this forum so appologise if this si a stupid question.

I am in the market for a new condensing boiler and have had 2 quotes. The first engineer recommended a Worcester Greenstar 24Ri to replace my 20 year old Olympic(50k BTU). He said that I would need a new 22mm gas inlet pipe running from the gas meter. My present pipe is 15 mm (I think). Anyway I had BG round for a quote and they said I would not need an increaded size pipe. Who is telling the truth? BG recommended a Glowworm HXI.

I'd rather not have to have a new gas pipe installed but the BG quote was just silly money.

Any advice would be much appreciated.

Cheers.

 

[scatmanjohn]

Two different boilers...they may both be correct.

 

[JB Gas]

WB say the RI needs a 22mm connection because the gas connection on the boiler is in 22mm, WB say it should be that size all the way. The hxi has a 15mm connection, dependent on gas pressures and flow rates supply can be left in 15mm.

 

[doitall]

24 Hxi 2.58 m³ h/hr

24Ri 2.6 m³ h/hr

Therefore, unless you're meter is within 3m of the boiler with no bend, tees or other appliances, the gas pipe will need to be a minimum of 22mm.

 

[Gasguru]

The gas pipe size has NOTHING to do with the connection on the boiler.

The size of the pipework is calculated to give a maximum pressure drop of 1 mbar from meter to boiler and is based on the pipe length, no. and type of fittings, the gas flow rate requirement and any other appliances on the run.

Some current combis will require 28 or even 35mm pipe.

Ask to see their calculations if they think you can get away with 15mm

Many boiler manufacturerers say 22mm since they know the boiler will have half a chance of working and they are fed up with customers (and installers) telephoning the support desk with problems with undersized supply pipework.

 

[corgiman]

must say that doitall has nailed this one

 

[JB Gas]

BG do not normally fit 24hxi as they have got the 330 which is an hxi which has the ability to vary the output using the fan speed. The 24RI will moderate itself down to the load required as it can be fitted on 22mm system pipe work as long as the load does not require 28mm pipe work but regardless of how close the boiler is to the meter WB say all pipe work must be in at least 22mm. The issue here is if correct gas rates can be achieved with 15mm even on a 18ri with a 22mm gas connection WB will say it is wrong and that will affect your warranty.