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Required Gas Pipe Diameter (Read 28524 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 !!!!!!

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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

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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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