22mm Gas Pipes and New Boiler

[Jo Silva]

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?

Thanks in advance,

Jo Silva.

[Toby]

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

for a bit more info.

[Christian McArdle]

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.

[Martin]

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

***

[Ed Sirett]

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.

[Jonathan Curtis]

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!!

[PoP]

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

[tarquinlinbin]

Why dont you believe him ?

[Steven Briggs]

In message , Ed Sirett writes

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.

[L Reid]

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!)

[Jo Silva]

Because I am cynical and don't believe everything I am told;)

No, if this is true then I am wandering how the current high output broken boiler ever got installed in there in the first place(it's not that old). When I bought the flat (two years ago) shouldn't the survey have indicated that this is a problem? The full run from the gas supply to the boiler is around 25 feet. It runs under my nice laminated glued down living room floor, thru to the kithcen to service the gas hob and then carries on to the boiler at the back of the house. I don't want to have to dig up my floor unless really necessary. But it looks like I will have to.

Thanks for all the replies,

Jo Silva.

[Christian McArdle]

Incompetently, by the sounds of it. I suspect there will be well over the standard 1mb pressure drop, but some boilers can cope with low pressure without too much difficulty.

The survey wouldn't normally cover something like this. In fact, the survey normally has some lines such as "the heating system was not tested" or such like.

Christian.

[Tony Bryer]

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?

[Christian McArdle]

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.

[Tony Bryer]

Not totally: a certain free program 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

[IMM]

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.

[Ed Sirett]

Yep, Agree. The better surveys usually cover themselves with "if you are uncertain of the condition of the gas/heating/plumbing installation" you should obtain a report from a specialist.

Then it would depend on how thorough a specialist you got in.

The OP has not told us either the heat input of the old or proposed new boilers.

[John Stumbles]

'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

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[Steven Briggs]

In message , John Stumbles writes

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.

[Andy Hall]

There are some application notes on this at the Copper Development Association web site,

complete with worked examples for different pipe sizes and all the data.

.andy

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