15 or 22mm Gas Pipe

[Kewat66]

Hi All,
Just trying to get some clarification on the 15 or 22mm gas connection. I have a colleague who insists on getting all his installs changed to 22mm. I have also had confirmation from clients that BG insist on this as well but I was working under the rule of pipe run with bends and other gas appliances at max being under 1mb drop from meter to boiler?
Most boilers appear to have 22mm connections but I am fitting a Glowworm flexicom this week that has 15mm gas connection, so do you always follow manufacturers instructions but hat applies when not mentioned in the MIs?
Thanks
Kewat66

 

[AWheating]

i worked on a HA job where they decided to fit isars because they had a 15mm connection and would work on 14mb inlet pressure. I refused to connect them up on the existing carcus and told the clerk he was an idiot and did not understand the regs and pipework sizing. As you can imagine i was removed from the job because i knew what i was doing and could not convince them that the size of the gas connection on the boiler has no real relevance to the actual gas supply needed.

 

[Richie_77]

Dont WB let you have a 2.5mb drop between meter and boiler?

 

[smtplumbing]

At the end of the day I upgrade all my boiler installs no problems. I learned the hard way one time so lesson learned

 

[Heating-eng]

Lameplumber,
yes this week i have had 3 quote installs following on from BG where they have stated all pipe work must be upgraded but in 2 of the quotes i worked out the runs were fine and within the correct tolerance. When i checked with a gas friend he backed them up, always changed to 22mm and insisted i was wrong! Just wanted clarification as this area seems a bit grey with MIs etc. If the MIs insist follow them if not you the pipe run calculation.

read instructions for boiler ,most WB boilers need 22 mm min

 

[GasmanxxxR1]

Dont WB let you have a 2.5mb drop between meter and boiler?

No, 1mb between meter and boiler, 1.5 mb between boiler and test nipple

 

[Heating-eng]

No, 1mb between meter and boiler, 1.5 mb between boiler and test nipple

All pipework for gas needs this, most boilers need at least 22mm even some of the heat only boilers need 22mm

 

[Reg Man]

Consultancy I got called in for on block of 50 flats. All design pipe sizing on original drawing was very border line. All pipe runs were long from communal meter room to each flat, run in track pipe buried in the carpeted corridor floors. Installer had decided to save money on materials by dropping down one size, bearing in mind 75metres of 40mm Tracpipe costs about £2K, he saves about £300 to 400 every 75metres. Result is working pressure differentials of up to 9 mbar on some runs, the boilers keep breaking down. Cost of all the corrective work must have been £100's of K's. I hope someone had good insurance.

 

[Killy Bing]

WB says no less than 22mm at any point in the gas run

 

[Heating-eng]

WB says no less than 22mm at any point in the gas run

no they don't, they say no smaller than the boiler connection, some will work on a small amount of 15mm. Not combis

 

[GasmanxxxR1]

WB says no less than 22mm at any point in the gas run

Depends what boiler, RIs can have 15mm now

 

[Heating-eng]

Depends what boiler, RIs can have 15mm now

even 22mm is too small sometimes, been to quite a lot on 22 with undersized gas.
need to do your pipe sizing correctly at the quoting stage.

 

[AWheating]

i dont really get this use of the statement's "this manufacturer said this" and "this manufacturer said that".

it does not really matter what they suggest, a 15kw worcester or 15kw baxi or a 15kw whatever, no change in what is required. what matter's is you design/size the pipework correctly.

Most of what manufacturers state in there instructions is used by engineers as an excuse from my experience. If your using manufacturers instructions to help you decide or excuse what size gas supply you fit then you need to reevaluate your methods imo.

 

[Heating-eng]

i dont really get this use of the statement's "this manufacturer said this" and "this manufacturer said that".

it does not really matter what they suggest, a 15kw worcester or 15kw baxi or a 15kw whatever, no change in what is required. what matter's is you design/size the pipework correctly.

Most of what manufacturers state in there instructions is used by engineers as an excuse from my experience. If your using manufacturers instructions to help you decide or excuse what size gas supply you fit then you need to reevaluate your methods imo.

i agree in part but it does matter what the manufactures say, worcester did say 22mm for a 12kw boiler and you had to comply ,now they say 15mm is ok,
You still need to size the house correctly.

 

[Ch4 plumbing]

Dont WB let you have a 2.5mb drop between meter and boiler?

Not when commissioning the boiler, I think they say upto 2.5mb drop on an existing boiler (service) but that's just going on memory.

 

[AWheating]

i agree in part but it does matter what the manufactures say, worcester did say 22mm for a 12kw boiler and you had to comply ,now they say 15mm is ok,
You still need to size the house correctly.

the only thing the manufacturer has control over is the connection on the boiler. If you size the pipework correctly you will never not comply with the manufacturers instructions. All they are concerned about is low gas pressures when they attend a warranty call tbh which is why they sometimes state a min size to try and stop poor installs. You cant blame them for wanting to recommend a min pipesize when they attend alot of poorly fitted appliances.