working pressure at meter

[manx12]

Installed a worcester bosch floor standing 550 in a 3bathroom house. During the commissioning process the standing pressure at meter was 24mb. when the boiler was put up to maximum temp/heating the working pressure at meter was 8mb.
The customer was made aware and transco was called out to check the meter/pipe etc.

when the transco guy comes he says to the householder "what is this semi industrial boiler doing in the house" (i was on another job when they arrived). And that the boiler need a huge amount of gas to work and that they need a new gas main putting in from the road.
Of course customer is back on the phone to me and i explained that it was a domestic boiler (basically it is a 42kw cdi with a hot water cylinder stuck on the side of it) and nowhere in the installation manual does it highlight a need for a new gas main..
Has anyone had an experiences of transco/national grid etc...
And any thoughts of solutions....

 

[radswilldo]

How was the boiler working at 8mb!. What was the inlet pressue at 8mb! Is the gas off at the moment?. To me this can only be one of two faults. The governor is at fault (donkin valve) or the main is decaying. Never come close to seeing 8mb, had 17mb, southern gas came out, main decaying, changed valve and let some of the corrosion fly out, got it up to 19mb. As you know 19-23 is meant to be supplied, if between 19 and 14 the customer will have to pay for the main, the gas transporter will only pay if under 14mb. So if customer has 19-14, they either pay for the main or wait till the gas transporter gets around to doing it by schedule, until which time the customer will have no gas. This is what i discovered after contact with both corgi and transco back in 2007. Personally i would of thought the governor is at fault. I trust the installation has been made safe regardless.
Forgot to add that its consumes 4.4cm3 of gas per hour, is made for domestic properties with high hot water demands but limited space. Gas supply from metre would be upgraded to 28-35mm depending on length of run and restriction. Every manufacture produces a boiler similar to this for the domestic market, Vaillant 937, gloworm 100sxi etc

 

[wnjswozo]

got to be govener ,what was inlet pressure at boiler?
i would check pipe sizing,22mm might not be big enough,may need a run of 28 from meter.

 

[Plucky]

Regardless of pipe sizing to the boiler if hes only getting 8mb working pressure at meter thats all its ever going to be. Transco arent trained to CEN1 or the likes. Pipework and Meters is about all they have.

So for him to say that to your customer is out of order. I have seen 11mb working pressure at meter before and Transco changed governor and all was fine after.

 

[manx12]

I agree i thought it was a faulty governor... the boiler is located less than 4 meters from the meter(including 2 pulled bends). i will try and push the customer to get them to change the meter/governor...before they start digging...(it is an old gas meter....it is worth a try)

 

[radswilldo]

What is the latest regarding transco

 

[andrewtheface]

28mm etc from the meter is all very well but what about the fact your gas meter union is 22mm !

 

[manx12]

conclusion..
transco put a new gas line with an external box , more or less in the same position as the old internal location.
We have connected the old gas meter in the new location and ran 22mm pipe to original internal 22mm gas pipe.
ran the boiler on max hot water and heating and got a constant working pressure of 20mb. Job done...

Also...
The Transco guy called me today to tell me the new gas main had been laid and that he noticed that the original pipe had been sleeved and must have restricted the flow of gas. He also added that they are doing alot of these upgrades due to new boiler's requirements.. And that there would be no cost to the houseowner... (we will wait and see).

 

[radswilldo]

Was the goernor new, they nearly always change them in this situation regardless, did he apologise for talking rollox about commercial boiler

 

[stevetheplumber]

28mm etc from the meter is all very well but what about the fact your gas meter union is 22mm !

preasure loss through the meter connector is negligable its on the lentgh of pipework
you can even start in 22 and upsize the other end of the run to increase preasure

 

[newbie1]

you would never do a run of 22mm and then upsize to 28mm you can reduce with gas run but never go from small to large

 

[stevetheplumber]

you would never do a run of 22mm and then upsize to 28mm you can reduce with gas run but never go from small to large

explain why ?
if you say you cant go from small to large how can you run a 28mm supply from a three quarter meter union?to increase available gas at an appliance you are reducing friction loss by increasing the pipesize

thinking about this more id like to see you run a 35mm main direct to meter its a struggle to get an inch bend in the meter box at the connector

 

[newbie1]

jst going on what i have been taught which is not to go from smaller bore to larger as you will get pressure loss if ime wrong sorry but thats what i was taught
sure someone else will come on and explain the theory behind this

 

[radswilldo]

Nevermind 28mm at least there is a fitting for it, though restrictive. Try installing 35mm, you start with 28mm and increse up to 35mm as close as practically possible.

 

[stevetheplumber]

jst going on what i have been taught which is not to go from smaller bore to larger as you will get pressure loss if ime wrong sorry but thats what i was taught
sure someone else will come on and explain the theory behind this

didnt mean to jump on you there but you can upsize anywhere in the run to reduce friction loss possibly not the best practice in the world but sometimes needs must
if youve done pipe sizing you will realise that the bigger the pipe the less preasure loss doesnt matter where in the run the larger size is it will still reduce preasure loss
one example was a gas meter in a garage and22mm passing under a drive way into the house originally serving cooker and 55000btu boiler fitting a 90000 combi left us short of preasure so rather than dig up the drive we re run the internal in 28 and this lifted the preasure at the boiler to within 1 mb of the meter

 

[Plucky]

didnt mean to jump on you there but you can upsize anywhere in the run to reduce friction loss possibly not the best practice in the world but sometimes needs must
if youve done pipe sizing you will realise that the bigger the pipe the less preasure loss doesnt matter where in the run the larger size is it will still reduce preasure loss
one example was a gas meter in a garage and22mm passing under a drive way into the house originally serving cooker and 55000btu boiler fitting a 90000 combi left us short of preasure so rather than dig up the drive we re run the internal in 28 and this lifted the preasure at the boiler to within 1 mb of the meter

Exactly try and look it this way.

By jumping up a pipe from, say, 22mm to 28mm. You would not be looking at increasing pressure. But preventing losing more of it.

Say for example 40m of 22 tube, you may lose (for arguments sake) 1.2mb. But if you ran the first 5m in 22mm and upsized the rest to 28mm you might only lose 0.2mb in the first 5 metres of 22. But the other 35m of 28mm might show you a loss of 0.6mb. Here you would only lose 0.8mb which will bring you within 1mb tolerance.

So your not INCREASING pressure but REDUCING the amount of PRESSURE lost. Which if you think about it is what we always do with gas. We never increase pressure as we are given pressure at a set point, or there abouts, from a governor. We just aim for as little pressure loss as poss.

 

[Bernie2]

I would agree with Plucky. Its only the outside edges of the gas flow that come's into contact with the walls of the pipe, the centre flows faster. So the bigger the pipe the bigger the centre flow or as said the less resistance to the flow, so less fall off in pressure.

 

[Puddle]

Newbie1 you are quite right, you should never upsize gas pipework from a smaller pipe size run, the practice can be quite dangerous.
Granted if you are going from 22mm to 28mm there probably would not be a big problem most of the time, but what happens if a fault on the governor occurs, still big a no, no, if the pipework was inspected, it would be cut off
You will cut down on resistance against pipework but also increase available volume in pipework, this will decrease preasure, the bigger the pipe difference the bigger the pressure drop
You may try the argument that the pipe size will be decreased again as it enters appliance and pressure corrected, all you have done is help it along its way, a few dead people have thought that
The gas will hit the appliance pipework at a lower pressure and then not increase but reduce again
Flow and pressure, increasing flow does not mean you increase pressure

 

[stevetheplumber]

Newbie1 you are quite right, you should never upsize gas pipework from a smaller pipe size run, the practice can be quite dangerous.
Granted if you are going from 22mm to 28mm there probably would not be a big problem most of the time, but what happens if a fault on the governor occurs, still big a no, no, if the pipework was inspected, it would be cut off
You will cut down on resistance against pipework but also increase available volume in pipework, this will decrease preasure, the bigger the pipe difference the bigger the pressure drop
You may try the argument that the pipe size will be decreased again as it enters appliance and pressure corrected, all you have done is help it along its way, a few dead people have thought that
The gas will hit the appliance pipework at a lower pressure and then not increase but reduce again
Flow and pressure, increasing flow does not mean you increase pressure

in that case almost every run of 28mm gas in london is ncs as they nearly all start with a three quarter meter connector

 

[migoplumber]

steve is totally right, in what he says. exactly for the reasons he and bernie has stated, most gas safe engineers know this as fact.

 

[Puddle]

in that case almost every run of 28mm gas in london is ncs as they nearly all start with a three quarter meter connector

You are now talking about a fitting,there would be no more restriction than a gas isolation valve
The point in question is running a gas supply in a smaller pipe size and then increasing it to a larger pipe size,this is not allowed and most gas safe engineers know that fact
The issue would be the ammount of gas that can pass through the meter and the pipework size supplying that meter,you should not be going over that size
As said in my previous post you may get away with 28mm from 22mm but that does not make it right, were do you stop 35mm from 22mm,100mm from 22mm

 

[stevetheplumber]

You are now talking about a fitting,there would be no more restriction than a gas isolation valve
The point in question is running a gas supply in a smaller pipe size and then increasing it to a larger pipe size,this is not allowed and most gas safe engineers know that fact
The issue would be the ammount of gas that can pass through the meter and the pipework size supplying that meter,you should not be going over that size
As said in my previous post you may get away with 28mm from 22mm but that does not make it right, were do you stop 35mm from 22mm,100mm from 22mm

i will take issue with one of your statements as i read it your saying pipework should not exceed the size of the supply pipe as my meter is supplied by three quarter barrel and i have a 28 mm service your saying this is wrong?

 

[Puddle]

The meter makes no differance to the point
You can have 3/4" supply coming into your dwelling and 28mm coming off,not because of your meter but because of the govenor fitted to the meter,this allows higher pressure to be supplied down the 3/4" pipework than is used on your side of the meter ,this makes it possible,because the pressure loss due to extra pipework volume can be compensated for,if the govenor was not there,just the meter,then no, you can not have larger pipework
And the size of the pipework you can have is governed by how much the increased pressure is on the supply side of the governor not meter
I would add and of course you will be restricted by the volume of gas able to pass through the meter

 

[stevetheplumber]

The meter makes no differance to the point
You can have 3/4" supply coming into your dwelling and 28mm coming off,not because of your meter but because of the govenor fitted to the meter,this allows higher pressure to be supplied down the 3/4" pipework than is used on your side of the meter ,this makes it possible,because the pressure loss due to extra pipework volume can be compensated for,if the govenor was not there,just the meter,then no, you can not have larger pipework
And the size of the pipework you can have is governed by how much the increased pressure is on the supply side of the governor not meter
I would add and of course you will be restricted by the volume of gas able to pass through the meter

not what you said first time "The issue would be the ammount of gas that can pass through the meter and the pipework size supplying that meter,you should not be going over that size"
im well aware of how a guvenor works

 

[Puddle]

not what you said first time "The issue would be the ammount of gas that can pass through the meter and the pipework size supplying that meter,you should not be going over that size"
im well aware of how a guvenor works

Sorry if I have offended you steve,of course I know you are quite aware how a govenor works,I thought we were just having a discussion about a issue,I did not mean any disrespect