Significant drop in gas pressure between meter and boiler

[donkeeboy]

Hi guys,

I had a Worcester bosch engineer out yesterday to look at my boiler, its been giving me some gip.

Turns out I need to replace CH pump, however during the work guy did a gas pressure test and said it was too low. Now my boiler cover plan from Worcester bosch is invalidated until I get the gas pressure sorted.

It was 13.3 at the boiler - and then 13.1 when the gas hob was going full blast. I have no other gas appliances. I need to have 16.5 at the boiler.

Then I got natrional grid out to test meter, as they changed it abut 6 months ago and I recalled the guy saying pressure was a bit on the low side when he changed it. The pressure at the meter was 21. He adjusted it a bit and said he cranked it up to 22 last night.

I just looked at the pipe work from the mains inlet, to the boiler. There is 0.5 metre 22mm copper coming out meter, then 0.5m 1.25" iron pipe, then 3m 1" iron, then the rest is 12 metres of 22mm copper all the way to boiler. 16 metres pipe work in all.

I counted the elbows, I got 22 elbows between the meter and the boiler. The engineer said yesterday you lose x amount of pressuure per elbow. Cant rememebr the amount, maybe he said up to 0.5 per elbow.

Anyonen got any views? I am losing a lot of pressure somwhere - got no leaks! With that amount of elbows, does it sound about normal to lose that amount of pressure? (22 down to 13.3)

Obv this aint the kind of thing I can sort myself, it's gas, would just like to hear some opinions so I can have some confidence in whats require to sort it out.

Thanks very much guys.

 

[GQuigley67]

why have you got so many tees ? have you got 22 gas appliances ?

 

[donkeeboy]

Oh crap - when I said tee's I meant elbows! LOL Sorry guys!

So 22 elbows - i just have the boiler and gas hob running on gas.

Just updated my OP to say elbow not tee to avoid any confusion

 

[GrahamM]

Firstly it sounds like a very poor install with so many elbows.
Did the Nat grid guy test the working pressure at meter? From your post it sounds like he has just upped the standing pressure by 1 mbar which is not getting you anywhere.
By sound of it you will either need the supply pipe from meter to boiler re-run or have the meter cranked up to a standing pressure of 25 or 26 mbar to give you the gas.

 

[donkeeboy]

Thanks Graham.

Yeah the boiler was installed 3 years ago by corgi guy, the gas pipe from meter is the original one from before, he just changed the bit at end near boiler.

I suspect your right about the nat grid guy. i was not here as he came last night instead of this morn as planned, I guess he just upped the standard pressuure as you say. That extra one mbar aint gonna help your right.

So is this all down to the nuumber of elbows do youu reckon?

Im sure some can be removed but not all that many to be honest, its a tricky run to the boiler in an unusual property.

 

[Bartdude]

When the boiler was installed the gas pipe should have been checked to make sure it was big enough for all your gas appliances.A calculation should be done to determine what size pipe you need. It sounds like that wasn't done which would mean the boiler has never had an adequate gas supply. Bad installation if that's the case but nothing unusual I'm afraid,there are a lot of "boiler swappers" out there.

Find a good Gas Safe engineer to check and uprate your gas supply,it probably needs to 28mm most of the way.

 

[Blackcatgas]

Aye, a nice big juicy length of 28mm and as few bends as possible.

 

[donkeeboy]

OK gents, thanks for your advice.

If there's any gas safe guy's on here in Leicester who wants to do this for me let me know.

 

[Billy Bob Bob]

28mm i have had to go as far as 1 1/4 once many years ago sadly inlet was 20 but the boiler was a Bahama hard to change it for a 105 then when it died LOL

 

[royston]

When the boiler was installed the gas pipe should have been checked to make sure it was big enough for all your gas appliances.A calculation should be done to determine what size pipe you need. It sounds like that wasn't done which would mean the boiler has never had an adequate gas supply. Bad installation if that's the case but nothing unusual I'm afraid,there are a lot of "boiler swappers" out there.


Agree with all of above.


Find a good Gas Safe engineer to check and uprate your gas supply,it probably needs to 28mm most of the way.

And this bit to !

 

[capitanpugwash]

Donkeeboy

You say: "I just looked at the pipe work from the mains inlet, to the boiler. There is 0.5 metre 22mm copper coming out meter, then 0.5m 1.25" iron pipe, then 3m 1" iron, then the rest is 12 metres of 22mm copper all the way to boiler. 16 metres pipe work in all."

If the 3m of 1" AND 0.5M of 1.25" iron are accessible and the rest is quite tricky, I may be inclined to change just the iron pipe initially. Having recommisioned the pipe and tested it, you may find that fixes your problem. It is obviously far better to change the whole lot and straighten out some of your many elbows, but the lead may have been knocked and being so soft could now have a restriction in it along the way somewhere. If it was my house I try this first. Having said that, you may be better of ripping it all out... Good luck

 

[donkeeboy]

Thanks Captain, thats very interesting, as the iron pipes are indeed far more accessible than the rest. I will connsider trying that first, cheers.

 

[Reg Man]

Firstly it sounds like a very poor install with so many elbows.
Did the Nat grid guy test the working pressure at meter? From your post it sounds like he has just upped the standing pressure by 1 mbar which is not getting you anywhere.
By sound of it you will either need the supply pipe from meter to boiler re-run or have the meter cranked up to a standing pressure of 25 or 26 mbar to give you the gas.

You can't crank standing pressure up. Standing pressure and working pressure are totally different things. Done this before on another thread. Standing pressure is controled by a device within a regulator housing, to stop excessive up stream pressure getting into your down stream pipe. Working pressure is controlled by another device within the regulator to control working pressure when gas is flowing through the pipe.

Restriction on this installation, may be caused by debris in the iron pipe. Another thing 16.5mbar at boiler required? If you have 21mbar WP at your meter you are required 20mbar WP on the inlet to your boiler under maximum flow conditions. Some boilers have the inlet test point on the boiler gas valve and additional restriction through the valve can drag the pressure down. If you have an isolation valve with test point at the boiler connection it will give a more accurate reading.

 

[SPC]

I work in Leicester. Give me a call if you want me to come have a look. Steve 07702155576.

 

[yorkieplumber]

Hi Reg Man its happening again lol

You can't crank standing pressure up. Standing pressure and working pressure are totally different things. Done this before on another thread. Standing pressure is controled by a device within a regulator housing, to stop excessive up stream pressure getting into your down stream pipe. Working pressure is controlled by another device within the regulator to control working pressure when gas is flowing through the pipe.

Restriction on this installation, may be caused by debris in the iron pipe. Another thing 16.5mbar at boiler required? If you have 21mbar WP at your meter you are required 20mbar WP on the inlet to your boiler under maximum flow conditions. Some boilers have the inlet test point on the boiler gas valve and additional restriction through the valve can drag the pressure down. If you have an isolation valve with test point at the boiler connection it will give a more accurate reading.

 

[Billy Bob Bob]

You can't crank standing pressure up. Standing pressure and working pressure are totally different things. Done this before on another thread. Standing pressure is controled by a device within a regulator housing, to stop excessive up stream pressure getting into your down stream pipe. Working pressure is controlled by another device within the regulator to control working pressure when gas is flowing through the pipe.

Restriction on this installation, may be caused by debris in the iron pipe. Another thing 16.5mbar at boiler required? If you have 21mbar WP at your meter you are required 20mbar WP on the inlet to your boiler under maximum flow conditions. Some boilers have the inlet test point on the boiler gas valve and additional restriction through the valve can drag the pressure down. If you have an isolation valve with test point at the boiler connection it will give a more accurate reading.

if you could crank up standing pressure there would be no such thing as depleted areas as reg man says standing pressure is what you have when you clip your u gauge on to the meter with no appliances running,working pressure is what you get with your appliance on max rate this can be adjusted up to 22mb,but we only want 1 mb difference trough out our pipe run if the pipes to small it wont happen ,gas pipes must be correctly sized sometimes cranking up to 22mb will give you 20 at the combi but starve the gas cooker when its going flat out in dhw and as we know most hobs/cooker tops in houses have no fsd so this becomes a very dangerous situation

 

[donkeeboy]

Thanks for the info.

I actually do have FSD on my hob. I find it bizarre that the gas//building/heating regs are so unbeleivably strict on everything yet most people have no FSD as you mention!

Anyway had a guy around to look at doing the pipework this afternoon.

 

[SPC]

I went round to look at this installation earlier. ive done the calculations and technically to achieve the 1mb pressure loss accross the line 28mm needs to be taken to within 5m of the boiler, which would prove arkward and costly. Worcester themselves state its acceptable to have a working pressure as low as 15.5 mb if memory serves me correct, which i think you would easily get by running 28mm for the first 6meters or so and take the hob feed from the 28mm and leave the rest of the 22mm in (roughly 15m inc elbows). So what do you guys think, do you A: do it 100% correct as the regs state and renew the complete line correctly sized for the appliances, or B: replace 1st section of pipework with 28mm and feed the hob off that supply and see if that gets you within worcesters tolerances?

sticky one to call like alot of situations gas situations.

 

[Reg Man]

Thanks for the info.

I actually do have FSD on my hob. I find it bizarre that the gas//building/heating regs are so unbeleivably strict on everything yet most people have no FSD as you mention!

Anyway had a guy around to look at doing the pipework this afternoon.

The standards are there for a reason. They are written to give best guidance on minimum requirements. They change from time to time because of incidents which occur, so revisions are made. So if the installation does not meet minimum requirements, there may be a risk of an unsafe situation.

 

[gas57]

why take a job on and not do it right you are only risking loosing your gas safe registration leaving a unsafe situation

 

[Gray0689]

I went round to look at this installation earlier. ive done the calculations and technically to achieve the 1mb pressure loss accross the line 28mm needs to be taken to within 5m of the boiler, which would prove arkward and costly. Worcester themselves state its acceptable to have a working pressure as low as 15.5 mb if memory serves me correct, which i think you would easily get by running 28mm for the first 6meters or so and take the hob feed from the 28mm and leave the rest of the 22mm in (roughly 15m inc elbows). So what do you guys think, do you A: do it 100% correct as the regs state and renew the complete line correctly sized for the appliances, or B: replace 1st section of pipework with 28mm and feed the hob off that supply and see if that gets you within worcesters tolerances?

sticky one to call like alot of situations gas situations.

If you change the first bit and you get to mi tolerances will it be right?
I don't think it will isit worth your gassafe ticket if they check it I don't think so
Do it right or not at all

 

[SPC]

how can it not be right if it conforms with manufactorers instructions (ie worcester state there boiler works fine down to 15.5 mb, and if increasing the first section to 28mm makes it say 17mb for instance). If it was an unsafe situation surely worcester would have allready deemed it AR when they went out too it and shut the appliance off (but they didnt they just said there not going to warrant the appliance as it doesnt comply with MI). increasing it to 28mm for the first section of pipework seems to make sense too me, if it brings it in accordance to manufactorers instructions, great, if not then the 28mm needs to be continued anyway just closer too the boiler.

However i take what your saying on board and to an extent agree with whats being said, if a jobs worth doing its worth doing correctly. I just dont like the fact that potentially next man will go in there and get the job by doing whats "necessary"

 

[Reg Man]

Manufacturer Instructions, for example Worcester Junior State "Installation and connection to this boiler must be inaccordance with BS6891" "Check the gas supply working pressure at the gas valve inlet point is not less than 18.5 mbar".

BS6891 require a minimum 1mbar dynamic working pressure differential over the pipe run. Working pressure at the meter should be 21mbar+/-2mbar.

So the Manufacturer has stated what is required. If their representatives are saying otherwise, then they should alter the instruction manual to suit, which of course they won't, because the boiler has been CE approved following the perimiters within the instruction manual, so therefore anything outside of the tolerance does not comply.

 

[donkeeboy]

This is for a WB Greenstar CDI 40 (regular). The WB engineer told me it was 16.5 for this boiler, he seemed sure of what he was saying. (Oh I aassumed a 'Worcester Junior' was a different type of boiler, I'm not so sure now I look at above msg again).

Anyway, the pressure at the meter (standard / workking .. whatever I dont know) is 22mbar.

 

[Reg Man]

This is for a WB Greenstar CDI 40 (regular). The WB engineer told me it was 16.5 for this boiler, he seemed sure of what he was saying. (Oh I aassumed a 'Worcester Junior' was a different type of boiler, I'm not so sure now I look at above msg again).

Anyway, the pressure at the meter (standard / workking .. whatever I dont know) is 22mbar.

Have checked instructions, They require the same requirements as previously stated, but require an inlet pressure of 18mbar. So unless Worcester are prepared to amend their instructions this is what is required. Doubt very much that they will do this as they would have to re-submit the appliance for CE approval under these test pressures.

 

[CMairiD]

With regards to WB appliances, it is worth looking at TB 115 & http://www.worcester-bosch.co.uk/cache/file/20/minimum-gas-operating-pressure.pdf

 

[Agile]

I dont see how any manufacturer can tell you how to opt our of a British Standard !

Whilst they may be happy as far as their boiler(s) are concerned that will not make your inadequate gas suppy meet the BS requirements.

Gas Safe use the BS and will rate you accordingly.

Since the customer always has to pay I dont see why so many RGIs want to do a bad job.

Tony

 

[MatthewHurt]

Each elbow is approximatley 0.5 Meters worth of pipework in terms of pressure loss on a gas instillation (so 22 elbows is adding an effective length of 11 Meters to the pipe run between your meter and boiler)
You should aim to lose no more than 1Mb worth of pressure accross the whole of the instillation (the furthest appliance I.E your Boiler should be running at 20Mb)
It sounds as if your current Meter - Aplliance pipe run is very badly done and needs replacing, Normaly I would guess it needs to be in 28 mm Copper all the way up untill it elbows up to the boiler (at which point it will need to be in 22mm)
The instillation should also be as straight as is possible

 

[Blackcatgas]

The gas valve on the Worcester is restrictive and you can lose 2mb across it on the test nipple, if you were to put in a test nipple on the 22mm pipe just before it goes into the boiler then you would most likely get a different reading.
Anyway lets say you commision a boiler at 3pm on a tuesday in the summer you might get the "correct" reading, then try commisioning the same boiler at peak demand time during one of the winters weve just had then you might not get it.

 

[SPC]

Each elbow is approximatley 0.5 Meters worth of pipework in terms of pressure loss on a gas instillation (so 22 elbows is adding an effective length of 11 Meters to the pipe run between your meter and boiler)
You should aim to lose no more than 1Mb worth of pressure accross the whole of the instillation (the furthest appliance I.E your Boiler should be running at 20Mb)
It sounds as if your current Meter - Aplliance pipe run is very badly done and needs replacing, Normaly I would guess it needs to be in 28 mm Copper all the way up untill it elbows up to the boiler (at which point it will need to be in 22mm)
The instillation should also be as straight as is possible

This is true, i've been there and worked it out. theres also an 11kw hob/oven approx 1/3 down the line. the 28mm needs to be ran to within 5m of the boiler to conform to BS.