Huge gas pressure drop between meter and boiler. Help!

[polesapart]

OP: phone Gas Safe and ask for an inspection.

+1

 

[davecon70]

If a heat only boiler was installed and it was replaced by a combi, the combi will be designed to have the heat capacity to heat up your hot water instantly, on demand. That means a boiler of perhaps double the Kw rating, double the Kw, double the gas flow too.

If you light your gas oven, gas hob, or gas fire, with the boiler not firing, if your then trigger the boiler to fire, does the oven/hob flame height decrease?

i put the biggest hob burner on and fired up the boiler- no change!

 

[Harry Bloomfield]

i put the biggest hob burner on and fired up the boiler- no change!

If there was a serious restriction or under-sized pipe, I would expect some change - assuming of course both were on the same end of pipe.

 

[FiremanT]

If there was a serious restriction or under-sized pipe, I would expect some change - assuming of course both were on the same end of pipe.

It has been established that there is a pressure drop, and the gas valve has been changed. Ergo: there IS a severe restriction or undersized pipework.

Has anyone looked at the inlet for evidence of sulphidisation. I assume the Worcester guy would have observed when he changed the gas valve.

 

[CBW]

I assume the Worcester guy would have observed when he changed the gas valve.

Vaillant I’ll let you off because of all the other posts

 

[davecon70]

It has been established that there is a pressure drop, and the gas valve has been changed. Ergo: there IS a severe restriction or undersized pipework.

Has anyone looked at the inlet for evidence of sulphidisation. I assume the Worcester guy would have observed when he changed the gas valve.

he did check and bashed the valve on its side after removing it. Nothing!

 

[Madrab]

@davecon70 , you need a (recommended if possible) independent GSRE in to do a full end to end survey of your gas supply to understand where your issue is. Ultimately he will need to test your supply at different points, trouble is if a lot of the pipework is hidden, inaccessible then that may be difficult and you may find that re-running the supply may be the easiest option. All of this is just advice on a forum, the final word and available options will be down to the engineer who will be onsite, can actually see what's going on and hopefully will offer the best advice.

 

[fixitflav]

It has been established that there is a pressure drop, and the gas valve has been changed. Ergo: there IS a severe restriction or undersized pipework.

Has anyone looked at the inlet for evidence of sulphidisation. I assume the Worcester guy would have observed when he changed the gas valve.

But following my #72, is there a problem or not?
Changing the gas valve sounds like a shot in the dark, an approach that has been criticised.

 

[BlueLoo]

@davecon70 , you need a (recommended if possible) independent GSRE in to do a full end to end survey of your gas supply to understand where your issue is. Ultimately he will need to test your supply at different points, trouble is if a lot of the pipework is hidden, inaccessible then that may be difficult and you may find that re-running the supply may be the easiest option. All of this is just advice on a forum, the final word and available options will be down to the engineer who will be onsite, can actually see what's going on and hopefully will offer the best advice.

Should a point to point check not be absolute?

 

[FiremanT]

But following my #72, is there a problem or not?
Changing the gas valve sounds like a shot in the dark, an approach that has been criticised.

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?

 

[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’m looking at the online manual.
Gas connection, boiler side 15mm
Almost all my pipe work is hidden which is a real headache. There is a mega flow under the boiler which hides everything and the pipes lead to behind a false wall. That might be my best chance to get an idea of the pipe size.
You are also correct- my experience so far with Vaillant is that when under warranty they do not really investigate- just replace and check the obvious.
Correct too- I have no idea if it was 20 millibar at both ends last year except the GSE saying that was the case and that this year it’s very different.

will have to update on Monday when he’s back but will also call Gas Safe for their advice.

cheers for everyone’s help so far.

 

[Madrab]

Should a point to point check not be absolute?

It may, it may not if every point is accessible, going by what the OP has intimated, it may not easily be.

We'll really only know once an experienced engineer visits, investigates, establishes the problem, offers and implements a solution and then the OP then tells us it's been fixed and tells us what the problem was.

 

[BlueLoo]

It may, it may not if every point is accessible, going by what the OP has intimated, it may not easily be.

We'll really only know once an experienced engineer visits, investigates, establishes the problem, offers and implements a solution and then the OP then tells us it's been fixed and tells us what the problem was.

Agreed.

 

[FiremanT]

I’m looking at the online manual.
Gas connection, boiler side 15mm
Almost all my pipe work is hidden which is a real headache. There is a mega flow under the boiler which hides everything and the pipes lead to behind a false wall. That might be my best chance to get an idea of the pipe size.
You are also correct- my experience so far with Vaillant is that when under warranty they do not really investigate- just replace and check the obvious.
Correct too- I have no idea if it was 20 millibar at both ends last year except the GSE saying that was the case and that this year it’s very different.

will have to update on Monday when he’s back but will also call Gas Safe for their advice.

cheers for everyone’s help so far.

Why are you looking online? Did you not receive a hard copy on the install?
In the hard copy you will find a Benchmark certificate. What pressure or gas rate is recorded?

 

[ScottishGasMan]

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.