Flue gas analyser reading

[Hardy1]

hi there,i done a flue gas analysis ona vailaint ecotec pro 28 the CO/CO2 reading was 0.0007 ,O2-3.6% and CO2-9.8%, the MI's state Co/Co2 reading <0.0031, C02 with appliance front closed 9.2 + or - 1% and CO vale with full load <250, could sumone please explain this to me as it has been a while since i done my CPA1, and could sumone please tell me if the boiler is operating safely or not?, thanks for your time, Hardy1

 

[mfgs]

Seems alright to me, was it on full rate when you tested it?

 

[AWheating]

seems fine to me, the ratio is good. the co2 of 9.8% is in the margin required by the manufacture (9.2% +- 1) and the 02 is in the 3-5% range.

 

[Hardy1]

so just to confirm?,- O2 should be within 5% range or am i getting confused?, could you please explain to me the readings please sorry its just been a long time and im just confusing myself, many thanks.

 

[REDSAW]

confusing it with a gas rate parameter of +/_ 5%

 

[Hardy1]

thats the one cheers lol, so when i get the readings just check them over MI's if there less or within range then im all good, if there higher then investigation required..., but if the mi's are not there, then what figure do you keep to 0.008? or 0.004?, and also what about the CO2 and the O2 readings what should they be when the MI's are not available?.

 

[yo1]

I think its in the unsafe situations guide, mostly boilers that are rated lower than A will not have a co2% stated by manufactures, so they may not state a co2% on older boilers or any flue gas readings for that matter.

 

[AWheating]

there are 2 ratio action levels of 0.004 and 0.008 that are used.

do you have your cpa course notes? it would be worth going through them. Its hard to remember alot of this stuff if you dont use your analyser every day, so i would suggest keeping some notes with your analyser or buying the pocket guide from corgi.

 

[AWheating]

Flue Gas Analysers Guide

 

[Hardy1]

yh thats true good old USSP lol, any1 else that can help me with the readings?, thanks for your time.

 

[AWheating]

0.004 and above service needed then retest.
then 0,008 and above further investigation required.

if the appliance has a cast iron heat exchanger it must be cleaned not matter what the readings are.

 

[Hardy1]

thankyou AWHeating just a quick question so 0.0007 is a fine reading isnt it? just want to confirm? many thanks

 

[AWheating]

yes, 0.0007 is very low compared to the first action level of 0.004. it can be confusing sometimes, especially if you get muddled up over the decimal point.

 

[mikimac]

Correct me if I'm wrong but isn't a reading of 0.007 classed as AR?

 

[Barry98]

.004 is what BG generally go by ive been told .008 for the rest of us mongs if no MI

 

[Hardy1]

so if at 0.008 then the appliance is AR?

 

[mikimac]

From the notes I have anything from 0.005 to 0.008 is AR. Anything above 0.008 is ID.

 

[Hardy1]

^^cheers mikimac, i just looked it up and was just about to say that beat me to it lol, cheers anyway thankyou, for all your lots time. also could sumone please explain the CO and CO2 and O2 levels aswell what should they be below? thanks again

 

[AWheating]

my notes say...

for checking to dertemine satisfactory combustion and subsequent actions needed as reguards service/repair your are looking for either:

within the manufactures stated figures
a co/co2 ratio is less than 0.004 (if no manufacture figures are specified)

if the values measured are outside these figures then further work is needed ie. full service,investigate and recify any faults, resetting of gas valve.

once this work has been completed take a further combustion reading, this reading must be either:

within manufactures stated figures
a co/co2 ratio of less than the action level for the type of appliance (if no manufactures figures are specified)

Action levels (co/co2 ratio)

central heating boiler 0.008
back boiler 0.008
back boiler and fire 0.020
flueless space heater 0.001
warm air heater 0.008
flueless oven 0.008
flueless grill 0.010 (or 0.020 no ce markings)

there are more

 

[Reg Man]

Don't get hung up on the readings to much. The Ratio is the most important reading. followed by the CO2%. On most modern day boilers with a zero govenor Ratio better than 0.0002 is good at between 9 & 10 CO2%.

The Ratio is worked out on the difference in quantity of CO within a CO2 reading. Therefore telling you if it is achieving efficient combustion.

Example: 200ppm CO..... 10%CO2 convert the CO2 to ppm by dividing by 10,000, then divide one into the other which gives you the ratio. Luckly your analiser does this for you. result Ratio 0.0002.

 

[JoGas]

A lot of the new boilers settings work on the CO2% some will not work properly or will give you out of range ratio's! if the high or low CO2% are wrong

Your readings are fine if within the MI's You can get vaillants off there web site

 

[tamz]

Many people seem to get hung up with 0.00?? numbers.
Your 0.0007 reading is 4.5 times less (or better) than 0.0031.

 

[Reg Man]

You should check the flue gas on high and low modulation.

 

[g60rge]

condensing boilers re check ratio will need to be below 0.004 soon according to my corgi book!

 

[Martyn crease]

If the reading is different when case is on then there's a problem with the flue can you take a sample reading of The fresh air going into the boiler ?