Pipe sizing.

[Spooked]

Hi all.
I have been having problems with gas pressure etc (see earlier posts).
I have had work done on my supply pipe by Transco.
I still have a few issues with pressure to my gas fire.
I have now been told that the pipe size installed by Transco could be lacking!!
They have run 22mm copper using approx 7.8m of pipe, 9 elbows and one formed bend from the new meter outside to the first T. This i'm told, with the fittings equates to 12.8m?
One opinion is that it should be at least 28mm over that distance as it is feeding a 31kw boiler, a 22.8kw range cooker and a 2kw fire.
I am fed up with differing opinions, is there somewhere on the web where i can get an answer, a definitive answer?
It amazes me how there can be so many different opinions, i thought that was the whole idea of an organisation like Corgi so everyone uses the same rules?
Cheers

 

[Nixt]

There are no rules regarding pipe size, only that the working pressure drop should not exceed 1mbar between meter and any appliance. Your pipe size is a mathematical calculation which anyone can do with the relevant information.

PS Corgi does not make gas rules, if you find out what they do then I'd be grateful if you could let me know.

 

[seco services]

it's not they don't use the same rules.
it's they can't pipe size.

 

[bab]

pipe sizes would be required but most engineers would of fitt the 28mm noing it to cope than risking an inadequte supply & one that cant be added later. Ya 22mm will give u about 3.7m3 per h of gas but iff all ya appliances or running at full which is what u must allow 4 when installing u need to deliver approx 5.4m3 per hr . if run in 28mm copper over that distance it would supply approx 7.5m3 per hr. more than u need. Sounds like they f up. Was it BG that fitted all works after meter.

 

[ChrisR]

the pipe size installed by Transco could be lacking!!
They have run 22mm copper .........

I doubt it. Who installed the pipe after the meter? Never heard of transco doing that.

 

[Spooked]

Thanks for the replies.
Nixt, there are rules, my nephew has just finished his course, exams next, and he has a chart that gives you a guide ie, my 2kw fire should not have any more than 20m of 10mm pipe supplying it assuming a straight run.
Yes, i know the working pressure is the defining factor but you must know what size to install in the first place surely? else you would have to pull the floor back up if you got it wrong.
I'm not knocking you, i'm only a layman, it is just so frustrating putting up with the mess and things yet it seems so hard to get the job done right at the first attempt. If this Corgi lark is so stringent then there should be no need to get things checked.

Seco, thats what i thought, thanks for the confirmation.

bab, thats what i was talking about, that to me is a general rule, you say i need 5.4m3 per hr so the 22mm is inadequate.
I shall ask for an inspector to call.

Chris, Transco installed the pipe work, they had to move an internal meter to an outside wall and so had to reinstate the gas supply.

Couple of other niggles, i am told there should be an earth to the new pipe work 600mm from the meter, there is no earth.
Also, the sleeve through the wall is 3 or 4mm inside the wall should it poke out beyond?
Also, how often should the pipe be clipped?
Thanks for the help.

 

[bab]

The earth should be within the meter & the 1st 600mm of the outlet pipework but visible. pipe clip centres change per pipe size 15mm pipe vertical 2m horizontal 1.5m 22mm 2.5 & 2m & the same for 28mm.sleeve should be at least flush with wall & sealed with non-setting compound

 

[Nixt]

Nixt, there are rules, my nephew has just finished his course, exams next, and he has a chart that gives you a guide ie, my 2kw fire should not have any more than 20m of 10mm pipe supplying it assuming a straight run.

Charts of suggested worked examples are not rules they are merely aids to achieve the only rule which is pressure drop. The example you've given is worked out to satisfy the input of the fire not because of any maximums permissible of a given pipe diameter.

 

[gas4you]

Forget the Kw of each appliance, you need to find the gas consumption of each appliance m3/hr.

Add them all together for the first bit of pipe work up till the first appliance Tees off, triple the equivalent length given, because there are 3 appliances then read what size pipe this needs.

This will give, in theory, 1/3rd mbar drop for each appliance in this section of pipe.

31Kw combi needs 3.3 m3/hr on its own, gas fire aprox 1, range cooker approx 2?

Chris, NG have re-connected many meters they have moved themselves around my way.

 

[Spooked]

Hi all.

Gas 4 You,
Assuming this calculation (kwh x 3.6 divided by 39) is correct?
The boiler = 2.9 m3/h (combi 31kw)
Cooker = 2.15 m3/h (range 22.8kw)
Fire = 0.18 m3/h (flueless 2kw)

Total of 5.23 m3/h

Does this seem right? If it is and babs calculations are near as damn it then the pipe work is under sized.

There is no sign of a earth wire any where near the meter, just a dangling earth left under the stairs where the old meter was.
There are no clips up the wall and the pipe is very moveable.

Nixt, i see, so is it the appliance manufacturers rules that must be followed?
Cheers all thus far, the call is looking ever more likely.

 

[ChrisR]

Ok I didn't see the meter had been moved.
Yes if they just put 22mm in without seeing what the load was then they got it wrong.

Spooked - the only rule is, it's gotta be big enough!
Yes there are tables , which I and others have to teach to.
They're totally innacurate though - way too small. You can't argue that the table says it's OK therefore it's ok.

 

[bab]

Quick note i didnt do accurate .jiggled the no,s and added n side of caution to show the large short fall. either way . pipes too small. was the installation pipework ok for size before meter was moved.was the meter within an equivilent length of 6m of less.?

 

[gas4you]

The Vaillants I fit, 31Kw, need 3.3 m3/hr, which is what I based it on.

Didn't realise you had a death trap of a flueless fire that is onlw 2Kw though.

I would assume that your total load is going to be nearer 5.6m3/hr, when the combi is supplying hot water.

According to BS EN 1057 pipe sizing table, which as Chris has rightly said should be used only as a guide, only 6m of copper would allow this amount of gas to flow, in your case with 3 appliances real length 2m.

If this were my installation I would only have the last 5m 'equivalent length' (= 15m with 3 appliances) in 28mm. Any pipe before this I would personally fit 35mm.

Although your meter is, I assume a G4 or U6, I would think that you are at the total limit of this meter supply your needs.

 

[doitall]

The pipe could still be the right size

Given the correct information and we could come up with an answer.

You have three appliances, label them C< E < F. A is the meter, B the first tee, D the second tee.

Then post the distances as follows plus the number of bends

A to B, B to C, B to D, C to E, D to F

Finally what appliance is on which leg

 

[Spooked]

Chris, this is what makes it so annoying, you all do these courses and you know what they teach you is sometimes a load of dung, you have to use your common sense in the end. After seeing the trail of destruction to decor and the workmanship of many 'trained' fitters i have come to the conclusion that the only reason i am not allowed to do a neater, safer fit myself is because i haven't paid thousands to the extorters to get a number!!
Oh yes, the wife agrees with your rule

gas4you, the meter is a U6
About the flueless, don't just say that, give me some facts, figures and examples and i WILL get my money back

These fools had a different route option, straight through the wall under the new meter, under the stairs back to the original entry point, total distance, less than 3 metres!![/quote]