Gas analyser readings

[Paul Barker]

With new modern boilers I aim for 0.002 co/co2 ratio, some achieve 0.001.

Gritish Bas guidelines are commonly accepted (stated in the Corgi manual actually) in the UK which are that 0.004 is a soft target and 0.008 is a hard target. That means that if it is between the two you should investigate. It is also accepted that after debris has been stirred up through maintenance temporarily the reading may be 0.008 and this is acceptable.

This practise corresponds to about 500ppm CO inside the flue gases (not by adjusted free air test).

So what we are saying is that CO of 500ppm inside the flue is worth investigating.

The Italians who use the absolute CO value as their guide method accept 1,000 ppm CO.

To put this in perspective, a band D combi with a boarderline fan performance such that the aps is flaging up a fualt intermittently, say where the fan pressure is 0.4 instead of 1mBar, would probably still be working at between 50 to 500 ppm CO or 0.004 to 0.008 ratio.

Now a boiler with fan in this condition I would consider delapi#dated and in gross need of attention.

Interesting to note in the light of recent events that the Italians would be fairly happy with a spider waiving a triangle shaped piece of paper in the flue!

Comments?

 

[oilman]

Scrap this inefficient gas heating, oil CO figures I expect to be less than 50 ppm, and typically are less than 30ppm.

 

[Paul Barker]

Very impressive, actually I find new gas boilers below 50ppm whether lpg or natural gas. Actually I am geting better results from lpg. Perhaps this is because it is more related to your oil than to methane.

 

[ChrisR]

Recently checked 3 Hamworthy 55kW gas boilers in tandem, each one, 0.0 ppm CO.

 

[ollski]

Solo 2's give a ratio of between .0020 and .0080 even when spotless, I don't know why. Almost all new boilers tend to ignore the ratios and give a percentage ratio or ppm which Bg are now under a strict instruction to stick to. The .0040 and .0080 ratios are only used when no figures are provided by the mi's.

 

[dan21mag]

installed a baxi recently, o.ooo6 mmmmmmmmmm

 

[oilman]

These small figures are all very well, but what is the calibration accuracy of the analyser. This will be %full scale + %reading +digits error. I know we just write down the figures on the display (because who cares?), but without the error budget, they're meaningless.

 

[Paul Barker]

Solo 2's give a ratio of between .0020 and .0080 even when spotless, I don't know why. Almost all new boilers tend to ignore the ratios and give a percentage ratio or ppm which Bg are now under a strict instruction to stick to. The .0040 and .0080 ratios are only used when no figures are provided by the mi's.

So do they use the 500 ppm figure then?

Alpha aim for ratio of .002

 

[chrishutt]

As far as I know, CO going up a flue and dispersing safely in the outside air is not a matter of great concern. It will presumably oxidise to CO2 in the atmosphere in due course. A certain level of CO in flue gases is actually desirable since it indicates that the boiler is operating at optimum efficiency. We should not try to improve on the manufacturer's recommended figures.

 

[oilman]

CO going up the flue is fuel going up the flue. It may well disperse and oxidise to CO2 later, but if it had done it before going up the flue the heat would be available in the boiler. CO is an indication of inefficiency, a MINIMUM amount of CO is the ideal. Some times (Hamworthy oil boilers) it's a struugle to get the manufacturers figures, let alone improve on them.

 

[Soggy_weetabix]

the venturi action, and subsequent poor flue gas anaysis readings seem irrelevent nowadays.

.02 is the british standard, which can be over 1000ppm.

If i was to suggest re-soldering the injector (and re-drilling) I am in for abuse even if the appliance is rated afterwards.

David

 

[ollski]

Thats a modification though isn't it which is against the rules and regs.

 

[Soggy_weetabix]

Thats a modification though isn't it which is against the rules and regs.

But 'solder can melt' when lighting back to injector as Ive been told.
Never happened and never will but the purists......

Appreciate your support ollski.

Dave

 

[chrishutt]

CO is an indication of inefficiency, a MINIMUM amount of CO is the ideal.

Not so. To eliminate all CO from the flue gases would require excess Oxygen (therefore excess air) to be mixed with the gas before combustion. This excess air (mostly Nitrogen) would have to be heated during the combustion process and would increase the volume of hot flue gases going to waste, thus decreasing efficiency.

 

[Soggy_weetabix]

With new modern boilers I aim for 0.002 co/co2 ratio, some achieve 0.001.

Gritish Bas guidelines are commonly accepted (stated in the Corgi manual actually) in the UK which are that 0.004 is a soft target and 0.008 is a hard target. That means that if it is between the two you should investigate. It is also accepted that after debris has been stirred up through maintenance temporarily the reading may be 0.008 and this is acceptable.

This practise corresponds to about 500ppm CO inside the flue gases (not by adjusted free air test).

So what we are saying is that CO of 500ppm inside the flue is worth investigating.

The Italians who use the absolute CO value as their guide method accept 1,000 ppm CO.

To put this in perspective, a band D combi with a boarderline fan performance such that the aps is flaging up a fualt intermittently, say where the fan pressure is 0.4 instead of 1mBar, would probably still be working at between 50 to 500 ppm CO or 0.004 to 0.008 ratio.

Now a boiler with fan in this condition I would consider delapi#dated and in gross need of attention.

Interesting to note in the light of recent events that the Italians would be fairly happy with a spider waiving a triangle shaped piece of paper in the flue!

Comments?

Yes I would like to comment,

BS states.02

That equates to over to 1000ppm with a CO2 reading of 5%

That is poor combution in my eyes.

Allowed...YES; but not with the acid raid thats melting my garden.

Poor combustion can be remedied with better Venturi (unless burner needs replacing) another post.

As an engineer, this is basic stuff.

David