Huge gas pressure drop between meter and boiler. Help!

[FiremanT]

It didnt have 20mbar working pressure at the meter and the boiler at the time of install, that's for certain. So any figures/commissioning readings provided by the installer cant be trusted.
You can either report your suspicions to gas safe who will probably do nothing about it. Or deal with it yourself. If its not affecting the hob then you dont have to do anything. get the same guy to service/check it next year and see if the reading has changed. Or upgrade the gas supply to it.

Which is my point

it seems that the last service guy was the installer.
He is suggesting changing the first section of iron
Unless he subsequently denies fitting the boiler , GS WILL do a free inspection if the OP complains and requests an inspection. If that is done, GS WILL issue a remedial notice.
I think any RGI following this will agree that the installer almost certainly cocked your.

To be fair, we all make mistakes, but this has the hallmarks of a hit and run

 

[davecon70]

I cannot see #no’s when on phone, so don’t know which post you refer to.
But the faked or erroneous 20mb at both ends show that there is no actual record of a correct pressure being recorded.
It is an odd thing, in that it is NCS to a following RGI, but a contravention by the installer- who is still culpable.

Re the valve - if a normal RGI did this, then it would be unprofessional and expensive. But as a Vailant warranty engineer there is no cost to the client. He would not be thoroughly investigating issues outside the boiler, so he did what he did to eliminate the boiler as the issue.

There is no debate - the issue is either a blockage in the pipework or the pipework is undersized.

OP: what is written in the Benchmark certificate?

I have the certificate-

Central heating mode
Burner operating pressure 20 millibar

domestic hot water mode
Burner operating pressure 20 millibar

When he and the Vaillant engineer tested at the boiler this week it was 13.5. At the meter it’s 20 millibar (tbc).

The gas flame on the cooker is not affected, the pipe work has not been changed for 20 years and 15mm inlet complies with minimum spec.

assuming static readings are correct os there anything that can cause this drop other than a blockage running up to the boiler. If that were the case you would expect some debris in the valve the engineer removed?

 

[ianmcd]

Central heating mode
Burner operating pressure 20 millibar

Absolute rubbish, your boiler does not have a burner operating pressure, it has a gas/air ratio gas valve, and if it did have a burner operating pressure it would not be 20 mb

 

[Harry Bloomfield]

The gas flame on the cooker is not affected, the pipe work has not been changed for 20 years and 15mm inlet complies with minimum spec.

I maybe missed it, but where is the boiler in relation to the oven/hob - are they likely to be on the far end of the same bit of pipe, in the same room?

 

[fixitflav]

Absolute rubbish, your boiler does not have a burner operating pressure, it has a gas/air ratio gas valve, and if it did have a burner operating pressure it would not be 20 mb

Not with you. Burner operating pressure I assume is a measured figure, so it does (or can) exist. My boiler has a tapping point after the gas valve, which I have used occasionally.
Having said that 20mb is clearly wrong. If the boiler is off, burner pressure is zero. If it's firing the pressure must be below 20mb as it is after the gas control valve. Perhaps he meant boiler inlet pressure.

My guess is the original testing wasn't done properly, and a correct test would have shown 13.5mb at the boiler, same as the latest test. In which case nothing has changed.

 

[davecon70]

Absolute rubbish, your boiler does not have a burner operating pressure, it has a gas/air ratio gas valve, and if it did have a burner operating pressure it would not be 20 mb

I'm sorry- I am literally reading out from the benchmark document. Does that imply what the GSE has written is rubbish?

 

[davecon70]

I maybe missed it, but where is the boiler in relation to the oven/hob - are they likely to be on the far end of the same bit of pipe, in the same room?

The oven is on the ground floor and about 5m from the gas meter/main pipe. My guess is the main pipe under the stairs feeds the oven (i seem to recall a plastic flexi pipe for that) and I assume copper pipework up to the boiler though it could be the same thickness as the pipe on the meter. How I would love to look under my floor!!!

 

[fixitflav]

I cannot see #no’s when on phone, so don’t know which post you refer to.

My #72 below. Replying to gas112 about supply pressure.

"OK thanks. I always understood the regs were as I said, but not for the first time, I stand corrected. I think somebody should tell the boiler manufacturers! Many of them say pressure at boiler inlet MINIMUM (their caps) 20mb. I believe Vaillant are in a minority in giving an actual requirement.

But is the consensus that the OP needs to do anything, or is it considered NCS?

If he does, and assuming the buried 8m section is 1” NB (OP – can you confirm the OD?), giving about 0.15mb drop at 3.2m3/h, replacing the 5m of 15mm pipe with 22mm should do the trick. Estimated drop in that section about 0.3mb, so total well within the 1mb allowed. That might not be too big a job.

Edit - before doing anything, a good idea to install a tapping point on the boiler inlet pipe, and do some proper drop tests"

 

[FiremanT]

Not with you. Burner operating pressure I assume is a measured figure, so it does (or can) exist. My boiler has a tapping point after the gas valve, which I have used occasionally.
Having said that 20mb is clearly wrong. If the boiler is off, burner pressure is zero. If it's firing the pressure must be below 20mb as it is after the gas control valve. Perhaps he meant boiler inlet pressure.

My guess is the original testing wasn't done properly, and a correct test would have shown 13.5mb at the boiler, same as the latest test. In which case nothing has changed.

Is your boiler quite old?
Modern boilers have Zero Governor’s. If you try to measure the burner pressure it will be zero or less .

So the benchmark is wrong. If he measured and meant the inlet pressure then it would , given the pipe run, would hardly likely to be 20mb, reflects zero pressure loss.
So, yes, the figures are probably faked.

 

[gas112]

I'm sorry- I am literally reading out from the benchmark document. Does that imply what the GSE has written is rubbish?

the line in benchmark your reading starts with burner operating pressure but if you follow line across it says OR inlet pressure is it inlet pressure he has written 20mb

 

[ianmcd]

Not with you. Burner operating pressure I assume is a measured figure, so it does (or can) exist. My boiler has a tapping point after the gas valve, which I have used occasionally.
Having said that 20mb is clearly wrong. If the boiler is off, burner pressure is zero. If it's firing the pressure must be below 20mb as it is after the gas control valve. Perhaps he meant boiler inlet pressure.

burner operating pressure, and appliance inlet operating pressure are two completely different things

 

[ianmcd]

I'm sorry- I am literally reading out from the benchmark document. Does that imply what the GSE has written is rubbish?

yep he has just made that up

 

[davecon70]

yep he has just made that up

A few have asked if I can send pictures- do you have to convert to a URL as I cannot seem to just attach a pic!

 

[ianmcd]

No bottom right hand corner of the post "upload a file" then select the pic and then post reply

 

[lloyda]

Just copy and paste your image into the compose box (where you type)