Low pressure at boiler - advice from Gas Engineer please

[ianmcd]

Well as you like to be so pedantic its actually mbar and not mB but just about sums all your posts up you have no interest in actually helping anyone out you just like to pick tiny holes in someones helpful post

 

[CBF]

Ian i would be grateful if you could point me to the updated BS or TB which states this, BS6891 & TB129 both state the meter outlet should have a min working pressure of 19mb which should give you 18mb at the boiler test point or upto 2.5mb less on the GV test point, if this was the OP's case then you could have 15.5mb at the GV as the OP said they have 14mb then this is AR, just because the MI states it can work on lower pressures is like i said neither here nor there it goes against both gas regs & BS & means the gas supply pipework is undersized

 

[ianmcd]

Sorry but it doesnt mean that the gas supply is undersized, yes this is a common cause but could also be a blockage in the gas supply that has occured since the supply was correctly installed and the correct sizing calculations were used, surely you must be aware that MIs can and do over rule GSIUR and BS on some occassions, if the manu says it is safe then it is not for me or you to over rule them , in the case of this BBU the manu would certainly say it was not safe to run at this pressure but a recent TB has stated that anything above 14mbar(see Tony) is only NCS and 14mbar or below is AR, no I dont agree but who am I to agree or not

 

[Agile]

Yes, I agree that the unit is strictly speaking "mbar".

Its commonly shortened to mb, or sometimes mB. The confusion with the capital letter arises because, in most cases, like Watt or Pascal they are proper names. Whereas bar and calorie are not !

I will try to write it correctly in full in the future !

Tony

 

[gaswizzard]

The only 'crock of ****e' on here is the 14 mbar reg , anyone with any savvy would be aware that most all burners can safely work down to 2 mb,,,Mb..mB .mbar MBAR. burner pressure.

is there an echo in here???????????????????/

 

[ianmcd]

No GW dont agree on that , yes most fully modulating appliances can indeed modulate down to around the 2mbar range but most older appliances have never been tested at such low rates

 

[nickso]

Most likely an exercise in arse covering. Sadly the current fear culture at Bg for safety is quite incredible.

Personally 14mB (hold that glazier you pedant ****) at a BBU inlet with all other appliances burning at max wouldn't bother me at all. As long as it doesn't affect combustion I pay it little mind. What is the max BP of most BBU's? 11ish mB? it's not going to bother it really is it.

For the OP.....what level of contract are the outlaws on? if they are on 400 the gas pipe is covered and any defects should be covered. At the very least I would have checked the filter on the inlet to valve....400 or not.

 

[gaswizzard]

No GW dont agree on that , yes most fully modulating appliances can indeed modulate down to around the 2mbar range but most older appliances have never been tested at such low rates

Take a look at the venturi type burner , gas/air ratio remains the same over a wide range of burner pressures (2mb/16mb) the burner on a gas hob may give you a clue

 

[ianmcd]

No GW dont agree on that , yes most fully modulating appliances can indeed modulate down to around the 2mbar range but most older appliances have never been tested at such low rates

Take a look at the venturi type burner , gas/air ratio remains the same over a wide range of burner pressures (2mb/16mb) the burner on a gas hob may give you a clue

Please quote me any Venturi type burner as you call them that a BBU incorporates that is circa 9 years old ? I have certainly never come across any ? all BBU burners that are that old are fixed rate and dont incorporate any venturis so quote all your hobs and winks all you want you are wrong

 

[gaswizzard]

Please quote me any Venturi type burner as you call them that a BBU incorporates that is circa 9 years old ? I have certainly never come across any ? all BBU burners that are that old are fixed rate and dont incorporate any venturis so quote all your hobs and winks all you want you are wrong

Are you for real? , most ALL atmospheric BBU used the venturi type burner , are you saying you have never come across a BBU that couldn't be range rated? if so you are clearly mistaken.

OP said boiler is circa 20 years old , if it's a 551/552 etc then these burners use the venturi which have the facilty to be range rated , same deal as with any other SE type burner that utilises the venturi. (most all of em )
Next time you pull the burner out take a look down the end. (are you a RGI?)

Just for the record most premix burners can work down to around 5mb inlet pressure with no adverse effects to combustion.

 

[Biggles..]

(are you a RGI?)

He's quoted in court as being an expert.

 

[gas112]

Namsag would love this post .

 

[Biggles..]

Maybe you could post on his behalf.

 

[fizzykoi]

My inlaws say the engineer did check the pressure at the meter and it was "ok" - so I assume that there is a pressure drop between the meter and the BBU (approx 8 meters), as you'd expect.
Anyway, your advise seems be be that they should get a second test/opinion from a private engineer, so I'll advise them to do that.

I'm just amazed that, whilst you all seem to know about the regs (though you dispute some of the minor details), nobody seems to know what the actual "risks" of low pressure are - pilot goes out? (surely not at 14mB?); boiler burns dirty?; boiler won't work at max output?; leaves on the line catch fire?
Seems I will get a different opinion depending on who tests the pressure...

 

[fizzykoi]

Good point Nickso - I'll get my inlaws to check the BG contract level they are on, but I suspect it's not the one that covers the supply pipe... or the BG engineer would have happily sorted it ... wouldn't he?...