Low pressure at boiler - advice from Gas Engineer please

[Biggles..]

There's a published piece of info available to all gas engineers I relation to excessive drops over installation pipework, what you should expect is that who ever turns up follows the unsafe situation procedures and In particular item 2.8

As long as min pressure for the appliance is met then it would have been NCS, if combustion or the safe working was affected then that should be escalated to AR/ID as appropriate.

 

[gaswizzard]

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?;

If the BBU is the only appliance on the supply then low pressure is not a problem due to the way these burners operate , if for example a gas cooker/hob were also on the supply low working pressure could extinquish the flame with both appliances operating (no FSD) , as said these type burners can run at very low inlet pressures with no ill effects to combustion.

The regs are put in place to be adhered too , whether they are right or wrong is a different matter.

 

[gaswizzard]

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?;

If the BBU is the only appliance on the supply then low pressure is not a problem due to the way these burners operate , if for example a gas cooker/hob were also on the supply low working pressure could extinquish the flame with both appliances operating (no FSD) , as said these type burners can run at very low inlet pressures with no ill effects to combustion.

The regs are put in place to be adhered too , whether they are right or wrong is a different matter.

 

[gaswizzard]

He's quoted in court as being an expert.

Wow...............be fun coming up against him.

 

[Agile]

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.

There will always be some pressure loss but if the pipework size is correct that will only be a maximum of 1 mbar ( ! ) and in your case that pressure loss seems to be quite a lot.

As you see, opinions vary as to what problems that will cause at the boiler and the reality is that its very little because the boiler is protected by a thermocouple which turns off the gas to the boiler is the pressure gets too low to establish a good size flame.

But we have to follow the regulations imposed on us and your boiler is apparently close to the point that it should be turned off but that depends on the exact gas pressure at the meter and boiler. Sometimes they can be brought back into the acceptable range at the boiler by increasing the pressure at the meter where it is allowed to be anywhere between 19 - 23 mbar.

As suggested, an independent often has more scope for making adjustments and interpreting requirements ( as you see from the discussions here. )

Tony

 

[CBF]

ok if i'm wrong i will admit it, so i'm sorry i guess i need to get a new copy of the USP, so to clarify from GS, anymore than 1mb diff in working pressure from meter to appliance is still AR, if this is ok then providing you can meet the MI with regard to min working pressure then it's NCS which is exactly what a couple of you have said

every day is a school day

 

[Agile]

CBF, I dont think that makes total sense.

As I see it, if there is more than 1 mbar loss in the pipework then the pipework is NCS.

At the boiler the maker's minimum inlet pressure must be achieved and if not then it will presumably be AR.

Seperately, and confusingly, there seems to be a statement somewhere that if the inlet pressure is less than 14 mbar then its AR regardless of what the makers say is required. I think that Ideal used to say their Icos/Isar could work down to 5 mbar.

Tony

 

[CBF]

Tony i have spoken to GS this morn with regard to this as i was doubting myself & someone said it had been updated so i wanted to be clear (even though i re did the ACS in july & nothing was said about it), neither the gas regs or BS have changed with regard to the 1mb that is still exactly as it was anything more than 1mb is AR, however & i'll take the OP's case 15mb at the meter outlet & 14mb at the boiler is NCS providing the MI states that the boiler will give max output at 14mb, however there is now another prob as we know there should be 19mb at the outlet but providing whatever is connected can all be run correctly with the min pressures req this is NCS, so now what do we do if all appliances are working correctly with only 15mb at the outlet ? NCS/AR, phone NG, phone a friend, ask a 12 yr old ? if anything i'm more confused than i was before i phoned them

 

[Biggles..]

Absolute garbage.

Re read 2.8 of your unsafe sits, more than 1mbar drop across pipework is and has been NCS.

And to clarify its 21+/- 2 at outlet of ECV.

To put your rather daft comment into perspective, look at it the other way.

23mbar at ECV, no loss through meter and 2through pipe to appliance. So 21at the appliance....is that At risk.

 

[CBF]

Absolute garbage.

Re read 2.8 of your unsafe sits, more than 1mbar drop across pipework is and has been NCS.

And to clarify its 21+/- 2 at outlet of ECV.

To put your rather daft comment into perspective, look at it the other way.

23mbar at ECV, no loss through meter and 2through pipe to appliance. So 21at the appliance....is that At risk.

I'm sorry Lee but unless you can show me updated amendments to BS6891 & TB 129 then you are wrong, more than 1mb drop across pipework is AR & always has been, with regard to my daft comment, you don't test at the ECV you test at the meter outlet & you could have upto 4mb loss across the meter, anything less than 19mb at the meter outlet should be reported to NG & if the MI req 20mb at the boiler & you can't get this & NG say we can only supply you with 19mb at the outlet & therefore 18mb at the boiler then this is AR, which is why you should always do a working pressure test at the meter before spec a replacement boiler because sometimes it's not just about the pipework it could be a incoming supply prob, how daft is an installer gonna look by AR a boiler they have just installed because the supplier can't supply the correct working pressure.

does this now mean you are gonna have to start using 22 & 28 rather than 10 & 15 for your gas runs ?

 

[Biggles..]

For the last time as I guess you were not taught on your short course or unaware as an unregistered installer that you should read 2.8 and 5.10 of the GIUSP where it quite clearly states that indersized pipework no affecting combustion and greater than the minimum input pressure is Not to current standards.

You cannot today install undersized pipework but anything previous is NCS!

Would you like a copy of the document!

 

[CBF]

For the last time as I guess you were not taught on your short course or unaware as an unregistered installer that you should read 2.8 and 5.10 of the GIUSP where it quite clearly states that indersized pipework no affecting combustion and greater than the minimum input pressure is Not to current standards.

You cannot today install undersized pipework but anything previous is NCS!

Would you like a copy of the document!

ok i'll play along, i have been s/e plumbing & heating for 32 yrs now wether that is a short course in your book i don't know & have never been an un reg installer, you are talking about two diff things, it was is & has been for as long as i can remember more than 1mb diff between MO & appliance inlet ie pipework only is AR, 2.8 ref to the MI it has nothing to do with installation pipework, 5.1 is an opened ended pipe connected to the gas supply so i'm not sure what that has to do with the price of fish ?

how many have you put down as NCS when they should be AR ?

i have spoken to GS this morn to clarify, if you don't believe me phone them yourself & then come back & i'll have a huge slice of your humble pie.

 

[Biggles..]

You can't even ****ing read 5.10, and 2.8 is very relevant as well.

 

[Biggles..]

32 years of overcharging customers by classifying something AR that's NCS.

No wonder gas engineers get a bad reputation.

 

[gas112]

Its feking frightening Lee , so adamant even after being told where to look.As they say you can lead a horse to water.