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Required Gas Pipe Diameter (Read 28525 times)
DoWellSon
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Required Gas Pipe Diameter
Oct 19th, 2004, 7:08pm
 
Looking at the Worcester-Bosch website for the Greenstar 28HE.
http://www.worcester-bosch.co.uk/index.php?fuseaction=product.literature&con_id=...
The Installation and servicing instructions on page 9 specify a max gas flow rate of 2.9m3/hr. Further down on page 10 it gives details of flow rate for different lengths of 22mm and 28mm pipe.
Why doesn't it give details of 15mm pipe? Since a 15mm pipe has about 40% of the area of a 22mm pipe would it not be suitable over short runs of about 1-2m?

Answers on a postcard please!
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« Last Edit: Oct 21st, 2004, 10:01pm by DoWellSon »  
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thescruff
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Re: Required Gas Pipe Diameter
Reply #1 - Oct 20th, 2004, 9:53pm
 
No !!!!!!

scruff
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #2 - Oct 21st, 2004, 1:58pm
 
..................and why not?
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Plumber
Re: Required Gas Pipe Diameter
Reply #3 - Oct 21st, 2004, 7:17pm
 
If you read the technical Data you will see that the gas connection is 3/4 and it states that 22mm minimum should be used.

If you are not competent and Corgi registered you should not be undertaking gas installations
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #4 - Oct 21st, 2004, 10:01pm
 
Doesn't actually answer the question. Provided you work out the pressure drop over the distance and confirm that the pipe diameter is sufficient to allow the required flow rate then why shouldn't you use a 15mm pipe? If you do the numbers you'll discover that 15mm is sufficient for this flow rate over about 1.5m

Quote:
If you are not competent and Corgi registered you should not be undertaking gas installations

Sorry, but I never actually said that I was going to undertake gas installation work. RTFQ please! Your 'factual' statement is in fact incorrect as there is no requirement to be CORGI registered only competent for the work which you are undertaking.
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« Last Edit: Oct 21st, 2004, 10:03pm by DoWellSon »  
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HandyJon
Re: Required Gas Pipe Diameter
Reply #5 - Oct 21st, 2004, 10:05pm
 
there is no requirement to be CORGI registered only competent for the work which you are undertaking.

So long as you aren't doing it for gain of any sort.

I suppose some pedantic person in the government could twist it to include increasing the value of your home so that when you sell you've made a gain because of your work.   Roll Eyes
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billythekid
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Re: Required Gas Pipe Diameter
Reply #6 - Oct 22nd, 2004, 12:45am
 
does that mean that i can put the kids in the back of the pickup since people should only be in the passenger compartment, them being there would make the bed a passenger compartment no?
Wink
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trowelhead
Re: Required Gas Pipe Diameter
Reply #7 - Oct 22nd, 2004, 5:09pm
 
ridiculous analergy! Grin(i cant find spell check!)
question: why is it only plumbers really get on there high horse? Grin Grin Grin Grin
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Plumber
Re: Required Gas Pipe Diameter
Reply #8 - Oct 22nd, 2004, 5:39pm
 
Hang on a minute I am not getting on any high horse, but it is a bit much when a DIYer such as DoWellSon starts contridicting the manufacturers, it does not matter one little bit what your calculation tell you if the manufacturer says it has to be 22mm pipe then it has to be 22mm pipe, no questions asked

That is why I answered the way I did, because I can understand when DIYers think they can disagree with us plumbers, but it is a bit much when they start thinking they know better than the manufacturers, if I read the instructions and it tells me to run 22mm I do it, I will not sit down and calculate to see if it can be done in a smaller pipe, manufactures instruction can overide any other regulation, so it is gospel in my book  
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« Last Edit: Oct 22nd, 2004, 5:40pm by REAL_PLUMBER »  
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trowelhead
Re: Required Gas Pipe Diameter
Reply #9 - Oct 22nd, 2004, 5:47pm
 
sorry Plumber,
my reply was not directed at you! 8)
Just one other point though,can a reg be over ridden by a manufacturers  instruction/guide?If it can then what is the point of a reg?  Roll Eyes  (interesting point1)
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thescruff
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Re: Required Gas Pipe Diameter
Reply #10 - Oct 22nd, 2004, 6:13pm
 
Manufactures instructions take president over the regs, as far as requirements are concerned

scruff
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thescruff
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Re: Required Gas Pipe Diameter
Reply #11 - Oct 22nd, 2004, 6:18pm
 
Dowellson ask a question and got an answer N0!!!! 15mm is not exceptable.

A competent person would not have needed to ask having read the book.

get an engineer that is.

scruff
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Plumber
Re: Required Gas Pipe Diameter
Reply #12 - Oct 22nd, 2004, 7:08pm
 
trowelhead, yes the manufacturers instructions take president over the regs, as thescruff correctly termed it
if for instance the regulations say that a terminal must be 200mm from a soffitt but the manufacturer of the boiler says you can place the terminal 50mm from a soffitt you can go with the measurement from the manufacturer if needed,(this is an example only)
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #13 - Oct 23rd, 2004, 10:16am
 
No-one has actually answered why you can't though.

Quote:
Hang on a minute I am not getting on any high horse, but it is a bit much when a DIYer such as DoWellSon starts contridicting the manufacturers, it does not matter one little bit what your calculation tell you if the manufacturer says it has to be 22mm pipe then it has to be 22mm pipe, no questions asked

Sorry, plumber but I beg to differ and this is why........
If you look at the Bregs approved documents for sizes of joists you will note that sizes are given for certain spans. However, should you do a structural calculation on the required span and find that a smaller joist can be used would any of you have a problem with that?

I grant you that a 22/28mm pipe gives a large safety factor and will be safe in all instances upto the lengths specified. Whereas, using a 15mm pipe you'd have to be a little more careful. This is where a scientific approach is need. The length of pipe, elbows, tees etc will all have a relative larger effect on the the 15mm pipe and therefore it should not be used unwisely. However, it doesn't mean you couldn't (unless you can provide scientific reasons why not).
To just except things could mean you don't understand why you're actually doing it, how much safety is built in and how far you can manipulate things. For example, the basic table may say you can only use 22mm pipe upto 15m so if you had a run of 15.2m could you still run 22mm? Well.........if you use the table no. However, if you did a calculation you may well discover that running it to 15.2m is actually no big deal, since the SF built into the table is large.

Quote:
Dowellson ask a question and got an answer N0!!!! 15mm is not exceptable.
A competent person would not have needed to ask having read the book.
I would suggest that a competent person would also provide a full explaination as to why not.
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« Last Edit: Oct 23rd, 2004, 10:21am by DoWellSon »  
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trowelhead
Re: Required Gas Pipe Diameter
Reply #14 - Oct 23rd, 2004, 10:17am
 
thankyou all Wink
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Plumber
Re: Required Gas Pipe Diameter
Reply #15 - Oct 23rd, 2004, 10:27am
 
DoWellSon

We have answered you can't because the manufacturer says you can't.

If you get a good installer in to fit the boiler, try telling him that you want him to run 15mm to the boiler even though the gas connection to the boiler is 3/4, if he is any good he will walk away

As I have said before it does not matter what your calculations tell you what the Manufacturer says has to be followed

So I will answer your question again No 15mm is not big enough to supply the boiler as a minimum of 22mm is required by the manufacturer

The scientific answer is we are regulated and we must follow the manufacturers instructions, why don't you ring Worcester and tell them they are wrong and that you have calculated that 15mm will be adequate to supply their boiler.

What have joist spans got to do with Gas

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« Last Edit: Oct 23rd, 2004, 10:35am by REAL_PLUMBER »  
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #16 - Oct 23rd, 2004, 10:55am
 
I guess Worcester specify 22/28mm because plumbers can't do complex calculations.

Quote:
What have joist spans got to do with Gas

Approved document..................standard regulations to suit most situations.
Scientific calculation...................more accurate assessment of situation.
Get the connection now?
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« Last Edit: Oct 23rd, 2004, 5:49pm by DoWellSon »  
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Plumber
Re: Required Gas Pipe Diameter
Reply #17 - Oct 23rd, 2004, 11:09am
 
I can assure you that I am quite capable of carrying out complex calculation, I size gas pipework for commercial installations which I can tell you are much more invoved than domestic calculations, but when it is written by the manufacturer what is the minimum size they require I do not question it

There is no relation between joist spans and gas regulations, especially if you can overide manufacturers instructions for joists, because you cannot overide gas manufacturers instructions
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JerryD
Re: Required Gas Pipe Diameter
Reply #18 - Oct 23rd, 2004, 2:53pm
 
DoWellSon, what is your problem?  You have been told by the manufacturer and by plumbers here, that 15mm cannot be used.  Why do you want to prove that it can??

The effort required to prove it is totally disproportionate to the end gain.

It's not as if 22mm copper is £500 a metre.

Jeeez, you could have installed the damn thing by now!!
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big_all
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Re: Required Gas Pipe Diameter
Reply #19 - Oct 23rd, 2004, 5:42pm
 
heeelllooo do well my son and wellcome Grin Grin Wink

now i am thoroughly intreaged do you have a special reason for wanting to use 15mm pipe
im not a plumber you understand just intreaged Grin Grin
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big all ---------------  we are all still learning
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #20 - Oct 23rd, 2004, 5:44pm
 
What I am asking is why it can't be used. No-one here has actually provided that. If you can provide a reasoned argument as to why you can/can't do something no problem. A building inspector would not object if you could prove why you had moved away from any guidelines if your calculations and logic were correct.

JerryD............I know copper tube doesn't cost that much but why waste it? There isn't an inexhaustable supply. If you could use a smaller diameter pipe why not use it?

Big_all........ In my case 15mm pipe is not suitable as the boiler is some 6m from the gas meter. However, as I've said can anyone here explain why you can't, for technical reasons, use 15mm pipe over a short run?
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« Last Edit: Oct 23rd, 2004, 6:04pm by DoWellSon »  
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JerryD
Re: Required Gas Pipe Diameter
Reply #21 - Oct 23rd, 2004, 6:26pm
 
The reasons you can't use 15mm is that it cannot supply enough gas!!

OK, you may be able to prove that it can (in certain circumstances) but the manufacturer's advice is to use 22mm.

This then covers 'worst case scenarios' and gives a reasonable safety margin.

Life's too short to argue about every rule and regulation, I just accept what manufacturers suggest and assume they have done the maths for me.  Like I said, the price difference is minimal (a few pence per metre) and as for 'wasting' copper, well.......................  Roll Eyes
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #22 - Oct 23rd, 2004, 6:40pm
 
Jerry..................Thank you. I accept that it covers all 'worst case' scenarios and whilst many people can calculate their own figures I would imagine that Worcester work on the principle that not everyone can or can be bothered to. Do you therefore accept that there is no technical reason why it couldn't be used in certain circumstances?

The reason that this thread is still at the top is that to simply state "NO!" with no supporting evidence is, well, odd.

rgds
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JerryD
Re: Required Gas Pipe Diameter
Reply #23 - Oct 23rd, 2004, 6:56pm
 
There has to be a cut off point when 15mm is not generally suitable and 22mm is suitable.  To calculate all marginal situations is not cost effective and cost is what we are talking about mostly as professional builders/plumbers/electricians etc.

To spend more than 30 seconds trying to prove that 15mm 'will do', and you start to lose money.  Just use 22mm as specified, do the job and type the invoice.  There can be no 'come-backs' as you've used the correct tube.  Anything less and you're open to claims.

The boiler manufacturer would probably cancel any warranty if the gas pipe was incorrectly sized.

I know what you mean though about being told 'NO' without any associated explanation, but for something like this where the cost difference is a couple of quid, I'd just accept it.

As an example of a more extreme situation, we had to build over an existing single storey extension once where the existing foundations were 'inadequate' according to the Building Inspector and he wanted everything underpinned.  The client then employed a structural engineer to 'prove' that the old foundations were adequate.  About £1,000 later the engineer did prove the foundations were adequate and the Council accepted his calculations.  Underpinning would have cost £13,000!!

So in this case there was big money to be saved by querying an instruction, but in the case of your gas pipe that's not so.
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« Last Edit: Oct 23rd, 2004, 6:58pm by JerryD »  
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Plumber
Re: Required Gas Pipe Diameter
Reply #24 - Oct 23rd, 2004, 8:20pm
 
DoWellSon

Here is your answer the reason you cannot use 15mm for this boiler is that 3 meters of 15mm pipe will only pass 2.844 m3/h the boiler requires 2.9, so 15mm will not be adequate to pass the correct volume of gas
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #25 - Oct 23rd, 2004, 8:30pm
 
Plumber are you removing my posts? A little unsporting don't you think? I responded to a moderator who was rather rude. Perhaps you need to have words with said moderator?

Thank you for your response regarding flow rate down 15mm pipe. I suggested originally that 15mm was okay for 1-2m though.............
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splinter
Re: Required Gas Pipe Diameter
Reply #26 - Oct 23rd, 2004, 8:35pm
 
Wondered what was happening,
read 28 posts then 24 thought the red wine had kicked in Embarrassed Grin Wink
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Re: Required Gas Pipe Diameter
Reply #27 - Oct 23rd, 2004, 8:36pm
 
I have removed several posts including some from scruff we are not here to start a slanging match, you asked a question and it was answered correctly by scruff you simply asked can 15mm pipe be used, the answer No, you did not ask can 15mm pipe be used and if not why.

Scruff is a very well respected contributer to this forum and his plumbing knowledge is far better than most.

I do not think he was been rude
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #28 - Oct 23rd, 2004, 8:37pm
 
Pity his behaviour is not equally as good.
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Plumber
Re: Required Gas Pipe Diameter
Reply #29 - Oct 23rd, 2004, 8:42pm
 
I feel your question has been answered and an explanation why, I have carried out the calculation and the volume of gas from 15mm pipe is not sufficient to supply the boiler in question, do you now agree that the question has been answered.
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splinter
Re: Required Gas Pipe Diameter
Reply #30 - Oct 23rd, 2004, 8:45pm
 
DoWelkSon,
              You little trouble maker Wink
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Re: Required Gas Pipe Diameter
Reply #31 - Oct 23rd, 2004, 8:52pm
 
Sounds like Charley Farley has passed on and beed re-incarnated. Wink
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OOPS!
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Re: Required Gas Pipe Diameter
Reply #32 - Oct 23rd, 2004, 8:59pm
 
It would be unlikely DoWellSon that you could get from the meter and connect to the boiler including allowing fittings valves etc which have to be added on to your total distance within 1 - 2 meters
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #33 - Oct 23rd, 2004, 9:30pm
 
Quote:
DoWelkSon,
    You little trouble maker

Not trying to cause trouble only make people think about things.
Quote:
Sounds like Charley Farley has passed on and beed re-incarnated
.................I can assure you that I am not CF. His postings on the 'other' forum are very rude and I would not resort to such personal abuse. Unfortunately, Scruffs personal abuse post towards me on this thread was removed by Plumber and so you can't see what he wrote.
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splinter
Re: Required Gas Pipe Diameter
Reply #34 - Oct 23rd, 2004, 9:43pm
 
DoWelkSon,
                We know you are not C.F he would have given reasonable back up to his theories ,Idid read the deleted posts was there any truths in them.Like I said not C.F more like CPW Wink
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Re: Required Gas Pipe Diameter
Reply #35 - Oct 23rd, 2004, 10:05pm
 
Fair enough,  I must also apologise for the spelling mistake Wink  beed??.

Grin
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DoWellSon
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Re: Required Gas Pipe Diameter
Reply #36 - Oct 23rd, 2004, 10:10pm
 
Sphincter Wink..............as Plumber has admirably demonstrated you can get the required flow rate down a piece of 15mm copper tube provided it is less than 3m long. I posed the question to get some reasoning for there being no column for 15mm pipe. The reason it would appear to be simply to cover 'worst case scenarios' and to avoid the need to do a calculation.

PS.............no I'm not a fat wire either Grin
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thescruff
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Re: Required Gas Pipe Diameter
Reply #37 - Oct 23rd, 2004, 10:51pm
 
[quote author=Plumber  link=1098209297/15#24 date=1098559214]DoWellSon

Here is your answer the reason you cannot use 15mm for this boiler is that 3 meters of 15mm pipe will only pass 2.844 m3/h the boiler requires 2.9, so 15mm will not be adequate to pass the correct volume of gas [/quote]

I final comment before it goes to bed Plumber.

The reason he can't use 15mm is because the manufacturers say so, end of argument.

scruff
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Re: Required Gas Pipe Diameter
Reply #38 - Oct 24th, 2004, 12:17am
 
DoWellSon

I stated that you are unlikely to be able to get from a gas meter to a boiler within 1-2 meters that is why the calculations start at 3m, none of the tables I have start at 1m they all start at 3m, so the answer is still No 15mm is not sufficient to supply the boiler as it will only carry 2.844 m 3 of gas the boiler requires 2.9 that is why the instruction state 22mm and 28mm only.

Please can you just except this answer

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