worcester bosch working pressure...

[moogwai]

I heard a fella in the plumbers merchant today say that worcester bosch accept a working pressure at the appliance of 16.5 mb on the cdi range!!! has anyone else heard of this???? He said he read it in the gas installer magazine a while back.

 

[newbie1]

read the mi dont take what joes uncle who spoke to veras neice who heard it from dave next door as the basis for your decisions

 

[moogwai]

hmm...i know,he said it's ok as you 1.5mb across the test nipple and the working pressure in the mi's is 18mb so that would make sense. I'll download the manual from their website and see for myself. Hopefully i'll bump into him again and call him an ar*e!!!!

 

[Blackcatgas]

This is ringing bells, I think, Il find the technical bulletin.

 

[Plucky]

Worcester's will actually operate perfectly on 14mb, but they wont put that into print as it really is on the fine line. That came from a Worcester rep.

I wouldnt advise leaving working pressures of 14mb anywhere though!

 

[wnjswozo]

as plucky says they work at 14mb,was told at nighttime mains pressure is reduced to reduce gas loss throu leaks in district,and manufactuers have factered this in

 

[Blackcatgas]

Worcester's will actually operate perfectly on 14mb, but they wont put that into print as it really is on the fine line. That came from a Worcester rep.

I wouldnt advise leaving working pressures of 14mb anywhere though!

Technical training bulletins - Worcester, Bosch Group UK installer site

This isnt the technical bulletin I was refering too, I cant find it but have found many refernces to it by other people that have seen it in gas installer magazine and as an adenum in the MI, 19mbar min at the meter- 1mbar drop across the pipe work, then 1.5mbar across the gas cock =16.5mbar. the above article states even lower though.
Corect me if Iam wrong but they are saying that min 15mbar at the meter- 1mbar drop across pipe work -1.5mbar across the gas cock, so it will run at 12.5mbar, not very well but Its okay?

 

[moogwai]

Blimey...it seems "the arse" who i heard was actually correct....glad i didn't say anything..he may have smashed my face in!!! lol

 

[stevetheplumber]

i have never got my head around this if worcesters can accept that sometimes gas is lower than 20 mb why havent others issued similar instructions
working on the scenario that you test working preasure when quoting for a boiler change you could then be in the situation that when its fitted you could find you have insufficent gas

 

[elite gas man]

16.5 Mb is all good providing you have Min 18mb at the gas meter and all others operating safely.




Ak

 

[T.T]

I'm new but just thought I'd share this, I've just had an Ariston Eco Combi working on 2.5mb pressure with 20mb at the meter, correct gas rate and G.F.A readings o.k.

I have switched it off and am going to upgrade the gas supply pipework.

 

[Blackcatgas]

I'm new but just thought I'd share this, I've just had an Ariston Eco Combi working on 2.5mb pressure with 20mb at the meter, correct gas rate and G.F.A readings o.k.

I have switched it off and am going to upgrade the gas supply pipework.

Hmmmm... Ive always wondered about this, zero governer, the fan sucks the required amount of gas needed to complete combustion so if you had a big plastic bag full of gas at 0 mbar theoreticaly the fan would draw enough gas under its own power to complete combustion until the bag was empty?.

 

[GrahamM]

I'm new but just thought I'd share this, I've just had an Ariston Eco Combi working on 2.5mb pressure with 20mb at the meter, correct gas rate and G.F.A readings o.k.

I have switched it off and am going to upgrade the gas supply pipework.

Let me get this right. You have a standing pressure of 20mbar, so where does the 2.5mbar come from? What is the inlet pressure (taken at the gas valve inlet test point)? I would expect somewhere in region of 19mbar.

Hmmmm... Ive always wondered about this, zero governer, the fan sucks the required amount of gas needed to complete combustion so if you had a big plastic bag full of gas at 0 mbar theoreticaly the fan would draw enough gas under its own power to complete combustion until the bag was empty?.

Yea the term 'zero governor' say it all. It more or less governs the gas pressure to closer to more or less 0 mbar so that as the gas reaches the venturi it is just sitting there at zero pressure going nowhere waiting to be drawn out. The fanned air rushing by creates a -ve pressure and pulls the gas out as per demand. As the fan speeds up there is more air, therefore more gas being drawn in to the combustion chamber.

 

[aggis]

Let me get this right. You have a standing pressure of 20mbar, so where does the 2.5mbar come from? What is the inlet pressure (taken at the gas valve inlet test point)?
The 20mbar at meter will be working as the 2.5mbar at boiler

 

[Bartdude]

The inlet pressure on the gas valve is the important figure here,what was that?

I think the 2.5mbar refers to the pressure on the gas valve outlet. If you only had 2.5 on the boiler inlet the gas rate and fga readings wouldn't be right.

I think you need to check it again at the gas valve inlet,you might save yourself a job.

Edit: unless you mean a 2.5 pressure drop from meter to boiler,just re-read my post and I may have misunderstood.

 

[GrahamM]

Exactly Bartdude. Not very clear!
Is the 2.5 mbar is the pressure drop across the pipework? That would make some sense although a 2.5 drop is very high and would mean a very poor installation.

 

[stevew451]

Gas safe man said pressure can decrease on the inlet elbow on the boiler

 

[T.T]

Gas safe man said pressure can decrease on the inlet elbow on the boiler

The standing pressure at the inlet test point was 19mb, working pressure was 2.5mb when running hot water.

I know it seems absurd that it would work at this pressure but as GrahamM mentioned maybe it is because of the zero governor.

 

[Billy Bob Bob]

baxi duotec 40 kw will not work on 17mb at the inlet they whine their heads off upset transco when they had to dig the drive up to put a new service pipe in

 

[tipintim]

It is correct. Its in gas safe mag

 

[GrahamM]

The standing pressure at the inlet test point was 19mb, working pressure was 2.5mb when running hot water.

I know it seems absurd that it would work at this pressure but as GrahamM mentioned maybe it is because of the zero governor.

Correct! There is no working pressure per say on a zero governed boiler. It is a meaningless reading.
Inlet pressure, gas rate & FGA is all you are concerned with.
It is not absurd! It is a fairly basic principle. Fanned air rushing by a venturi creates a -ve pressure drawing the gas out. You can simulate it with an empty bottle by filling it with smoke then blowing across the top. The smoke will be drawn out.