Gas pipe run

[bigcat]

Is a 25' run of 15mm supply pipe acceptable for a new boiler? Thats gas supply, not electric :)

I need to know fairly quickly this time. Boiler power 30-40 whatnots

thank you, NT

[IAN]

No It would not be acceptable for an older boiler

[Andy Hall]

Kilowatts? If so, then almost certainly no.

[Aidan]

Doubt it. My boiler's about 18 whatnots and the manufacturers specify

22mm pipe to within about 12 or 18" of the boiler. There might be something similarly specified in the installation manual for your boiler. You can't calculate the pressure drop (which is usually the criteria) without details of all the other appliances, pipe lengths, tees, etc..

[Christian McArdle]

No, if you mean kW. It might be OK for kBTus (an ancient unit), but calculations might be in order even then.

Christian.

[Alex (YMG)]

If you have a look here

you should be able to work out just what size you'll need (note the additions for 90 degree elbows etc.) and also how much extra capacity the pipe will have, should you wish to add any extra appliances at a later date.

Alex

[bigcat]

Thanks to everyone :) I am pretty ignorant on this, but assumed its kbtus. Its probably 30 odd years old. The 15mm supply has never been a problem in any way, but thats bureaucracy for you.

So I guess I'll have to run a 2nd pipe in parallel to lower the resistance. I've got an old hose reel somewhere...

NT

[Chris Bacon]

I bet someone'll be hooked - but who will it be?

[Christian McArdle]

If it has worked perfectly for 30 years, then leave it, unless it has failed an inspection. Without doing the calcs, and assuming few elbows, the run is probably just below spec. Perhaps someone will be kind enough to do the calcs for you!

Christian.

[bigcat]

Yep, its failed. A new run it is - wont be hard to do. Its the new boiler I'm unhappy about.

Oh, yes there was another appliance run off that section of pipe too. I guess I had modulation and didnt know it :)

cheers, NT

[Christian McArdle]

Ah. Another appliance will drop it much lower!

If the other appliance is greedy, you might even need 28mm to the split and

22mm after. There's no point in underspeccing the new run. Your next boiler might be a 40kW monster.

Christian.

[John Rumm]

Well if you take a m^3 of gas as 37MJ, assume the boiler is 40k BTU (11kW ish) that gives you 11000*3600 J / hour, or about 40MJ. So that is a gas rate of approx 1.1 m^3 / hour.

Lets call the pipe run 9m to allow for some bends etc.

According to:

of 15mm will be good for a gas rate of up to 1.5 m^3 / hour

So you look ok right up until the bit where you mention there is another appliance on the pipe! ;-)