# 22mm Gas Pipes and New Boiler

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• posted on November 13, 2003, 2:51 pm
Hello,
Firstly, apologies if I am repeating something that has already been answered. I've done a search and cannot find an answer to my question.
Basically I need a new boiler. I corgi registered bloke came round and told me this (I don't doubt him-the current one is leaking and not working).
He said that he would NOT install a new one for me as the gas pipes that run though my flat are smaller than 22mm, currently the pipe seems to have some sort of conversion part on it about 1/2 metre below the boiler and it is 22mm when it enters the boiler.
He also said no other corgi guy would do it either and told me I HAD to replace the pipes so they are all 22mm.
Is this true?
Jo Silva.
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• posted on November 13, 2003, 3:25 pm
Jo Silva wrote:

Quite likely, but ultimately dependant on boiler size & location. A tiny boiler near to the meter may be possible with 15mm pipe. The gas requirements of most combis and system boilers is something that can only be accomodated in at least 22mm pipework. The pipe size will be proportional to the length of the run and boiler size. Check Ed's FAQ http://www.makewrite.demon.co.uk/GasFitting.html for a bit more info.
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Toby.

'One day son, all this will be finished'
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• posted on November 13, 2003, 6:14 pm
On Thu, 13 Nov 2003 15:25:08 +0000, Toby wrote:

Thanks for saving me the bother of directing the OP to the FAQ. 8-) The OP's gas fitter is right but needs a lesson in customer relations if his style is as reported by the OP. As for 'proportional' that would be in the qualitive and not the mathematical sense. Available gas flow is inversley propotional to the equivalent length of the pipe and proportional to the square of the area (sic) yes the forth power of the pipe ID. Double the diameter, quadruples the area, quaters the gas speed which 16th the pressure drop.
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Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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• posted on November 13, 2003, 11:14 pm

Ed, read your FAQ, but do you have any pointers to resources for pipe sizing / flow calicos? I'd like to figure out how much of my boiler feed would need replacing if I fit modern higher power boiler. ISTR some ball-park figures somewhere in the past, i.e. 22mm good for X KW at Y run length, allowing additional Z per elbow sort of thing.
Ta.
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Steven Briggs

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• posted on November 14, 2003, 9:05 pm
writes

'Plumbing' by R.D.Treloar has the table and describes how to use it. So does BS 6891 but you can probably find Treloar in a good bookshop, and it covers most plumbing stuff at a reasonable level. Haven't checked Treloar against the BS but the standard has (small) errors in a couple of the figures! (Easy to see if you plot the curves.)
Roughly, for a 28KW boiler (about 3 cubic metres/hour) you can run about 20m in 22mm pipework, or 3m in 15mm (or pro rata for a mixture). Or right round the block in 28mm :-)
For each elbow add 0.5 metres.
-- John Stumbles -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -+ The astronomer married a star
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• posted on November 14, 2003, 10:16 pm

Thanks, thought I would be marginal. I reckon at the moment I've got 19m + 4 elbows in 22mm, plus 5m + 5 elbows in 15mm, feeding old glow-worm 60K BTU boiler. I would like to replace with a 25Kw condenser, probably a Keston. Even if I shortened the run to the shortest possible, all 22mm, would be about 18m + 6 elbows, so I'd probably have to do the easy in the house bits in 28mm. Not impossible, but it'll have to be taken into account for cost & time.
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Steven Briggs

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• posted on November 15, 2003, 7:51 pm
On Fri, 14 Nov 2003 21:05:53 +0000, John Stumbles wrote:

Thanks John. The OP should not that in general that most boilers are given in terms of there output rating i.e. 24kW needs 26.5kW of gas, 28kW needs about 31kW of gas. Bigger boilers and more recent models tends to be quoted in terms of their _input_ .e.g 37kW.
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Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
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• posted on November 14, 2003, 10:50 pm
On Thu, 13 Nov 2003 23:14:23 +0000, Steven Briggs

There are some application notes on this at the Copper Development Association web site, www.cda.org.uk complete with worked examples for different pipe sizes and all the data.
.andy
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• posted on November 15, 2003, 8:52 pm
[snip]

Thanks Andy, I think that's the one I remember. Measured up my pipe runs, squinted under the floor at the number of bends & elbows, thrown together a spreadsheet, and basically I'm stuffed. With the current 60Kbtu boiler, I've got 3.7mb drop at the boiler, and 4.37mb at the hob. Not surprising the hob drops a little when the boiler fires! The only way to achieve <1mb drop will be to move the meter, as there's over a millibar drop on the pipework from the meter in the garage to the house with a bigger (Keston C25) boiler.
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Steven Briggs

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• posted on November 15, 2003, 10:29 pm
On Sat, 15 Nov 2003 20:52:57 +0000, Steven Briggs

28mm pipe from the meter?
.andy
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• posted on November 16, 2003, 10:49 am

Thats the problem. The meter is in a detached garage, the first ~9m of pipe being 1" glav steel underground, its easier to shift the meter to a box on the side of the house than upgrade that section of pipe. I think sleeping dogs will be allowed to snooze.
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Steven Briggs

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• posted on November 13, 2003, 3:59 pm

Probably, although you might be able to find an old inefficient small boiler that could cope. A modern modulating burner type (condensing or not) would be hopeless on 15mm unless the run was very short. Would it be very difficult to run new pipe?
Christian.
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• posted on November 13, 2003, 6:22 pm
On Thu, 13 Nov 2003 15:59:19 -0000, "Christian McArdle"

I don't profess any expertise with the new gas regs, but I was under the impression that in the event that any work is carried out on a heating system then it is a requirement that the new regs are obeyed.
I may be wrong - others will no doubt jump in here and offer better advice if so.
PoP
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• posted on November 14, 2003, 12:20 pm
Christian McArdle wrote:

Perhaps I'm missing something, but why do you want an old inefficient boiler. Surely the way to minimise the gas consumption is a modern efficient boiler whose maximum output/ efficiency is within what the pipe can supply?
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Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser
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• posted on November 14, 2003, 1:20 pm

The problem is that efficient modern condensing boilers tend not to have low maximum outputs. You are largely limited to old inefficient boilers.
The real solution is to change the pipe.
Christian.
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• posted on November 14, 2003, 5:24 pm
Christian McArdle wrote:

Not totally: a certain free program <g> identifies the Ideal Minimser SE30 (no idea whether it's any good) as having a maximum output of 8.8kW and efficiency of 86.1% and there are quite a few others that are 8.8kW (30,000BThU) max.

I agree that you the best way forward is to choose the right boiler by the needs of the property and run a supply as necessary rather than choosing the boiler by the supply
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Tony Bryer SDA UK 'Software to build on'
http://www.sda.co.uk
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• posted on November 14, 2003, 7:26 pm

They are very good, very simple, and very reliable condensing heating boilers. I have one, although a larger size than that. AFAIK, they are no longer made, being replaced by the ICOS range about 18 months ago. They were briefly sold as the Henrad by B&Q, but this has now stopped.

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• posted on November 13, 2003, 6:13 pm
<snip> Probably true, but if it's just the pipe from the meter to the boiler, it shouldn't be too big (or expensive) a job; unless there's some difficulty in running the pipe? I'm somewhat surprised the guy didn't quote for the new pipe as well as the boiler; unless it's the time of year; there's bigger money to be made in servicing and repairs this time of year! but maybe I'm just a cynical old ***
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• posted on November 13, 2003, 11:32 pm

in
the
I'm getting a new fire installed in the dining room and as part of that they're replacing the existing 15mm pipe from the meter (which feeds an old fire and separate boiler) with 22mm. No extra cost (least I think not!)
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• posted on November 13, 2003, 6:14 pm
My boiler - a new baxi bermuda back boiler with gas fire needed half 22mm pipe and half 15mm pipe (we also have a gas hob). This is over a run that stretches 50 feet. Apparently it doesn't matter where the sections of 22mm pipe are put in so they were put in in the most convenient places. The previous boiler was of similar rating- a glow worm with gas front fire, the pipe was all done in 15mm after an extension 2 years ago (50 feet) by a corgi registered plumber, probably ran out of 22mm pipe that day!!
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