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Combustion analyzer reading

SlimpickinsSlimpickins Member Posts: 314
Could someone explain what the CO(0) reading is on a combustion analyzer. In the manual it just says, CO referenced to %O2

thanks in advance!


  • Steve WhitbeckSteve Whitbeck Member Posts: 669
    edited January 2013
  • TomTom Member Posts: 458

    o2 is oxygen

    co2 is carbon dioxide

    co is carbon monoxide
    Montpelier Vt
  • icesailoricesailor Member Posts: 7,265
    edited January 2013
    CO(*) Reading:

    I think he may be asking about the last reading that is listed on a Bachrach Insight display or printout.

    The first is O2 The next is CO. The next is CO2, The next is Efficiency. The next is T-Stack (Stack Temperature). The next is T-Air (room temperature). The next is Excess Air.

    The last is CO (*). The "(*) is a number that relates to CO or Carbon Monoxide. What does it mean?  I myself don't understand it except it might be an average of CO during a test run.

    At least that is what I think it is he asking and if it is, I don't understand it either.
  • Tim McElwainTim McElwain Member Posts: 3,904
    edited January 2013
    It is CO

    as it relates to O2 basically the same I believe as CO (AF) air free. It is the actual CO minus the O2.

    Actual CO have always been related to either O2 or CO2 in fact years ago we used formulas to find actual CO as compared to a diluted reading. The higher reading is always the actual CO reading.

    Some testers also have a NOX eliminator or in the case of Insight you can purchase an add on filter I believe. This will typically give much lower CO reading than one without it. Jim Davis has a real good explanation of this, I just can't seem to find it, maybe he will pitch in here and give it.

    By the way we will be running a three day "Testing Design Gas Equipment Class on Feb 5, 6 and 7 at our training center in Warren, RI, Call 401-437-0557 or e-mail [email protected] if you are interested.
  • icesailoricesailor Member Posts: 7,265
    CO (*) reading:

    I don't have access to my instrument, but I think that the CO (*) reading is always higher than the straight CO reading.

    I just went downstairs and got the results of when I cleaned my boiler.

    Before I cleaned it, the CO was 37 PPM The CO (*) was CO (2) was 44 PPM. After I cleaned it, it was CO 31 PPM and the CO (2) was 37 PPM.

    The EA is a tad high. I need to replace the door gasket and the bonnet gasket. The shoemaker always has holes in his shoes.

    Time to bring home some Lynn 3/8" rope. and a tube of high temp RTV.
  • SlimpickinsSlimpickins Member Posts: 314
    Thx Tim

    Icesailor is right, that's what I was asking and thanks Tim for the explanation. Actually I have the new Bacharach InTech analyzer that I just purchased and liking it so far. Tim, I wish I lived closer and wasn't so busy or I would attend your class.
  • Jim DavisJim Davis Member Posts: 578

    CO* is CO "Air Free" or no Oxygen in the sample.  This is a theoretical calculation that indicates that if there was no Oxygen(also called Excess Air) in your flue sample, this is how much CO the burner is actually making.  Based on your readings your O2 reading is around 3% which would not be too much excess air. 

    NOX is a by-product of good combustion and hot flames.  NOX interferes with all CO sensors and causes them to read 10-30ppm higher than the actual CO being produced.  We have have CO monitors go off in dentist offices because their N20 tanks(laughing gas) were leaking. 

    The only difference between an analyzer with a NOX filter and one without one is that the one without one might end up a little safer because you think the CO is higher than it actually might be.  In the field over the last 25+ years this has made no difference in the setup or tuning of equipment.

    I only use the "Air Free" CO to show the customer and maybe get them to react to our recommendations a little sooner.
  • icesailoricesailor Member Posts: 7,265
    CO (*):

    So, if I install the NOX filter on my Insight Analyzer, the first CO reading will stay the same? The second one "CO (*)" will go down?

    I only do #2 oil and LP GAS. I read somewhere that the NOX filter was needed for Nat. Gas but not much LPG or #2 oil.

    I'm teachable.
  • Jim DavisJim Davis Member Posts: 578
    NOX Filter

    Natural Gas, LP and Oil all make about the same amount of NOX in our combustion processes.  If you use it on one you would use it on all.

    NOX does not significantly interfere with our combustion readings to cause any problems.  It affects the CO reading and makes it slightly higher,  However, I have seen many times in the field that the analyzer with the NOX filter had higher CO readings than the one without.  I am talking about analyzers that are recently calibrated. 

    All CO sensors in different analyzers have different sensitivities.  It is almost impossible to get the same CO reading in a flue from two different analyzers, even the same make. 

    But lets look at what kind of difference a NOX filter versus a non-NOX fliter might make on a standand cast iron boiler.

    NOX filter analyzer readings:     O2 - 6%

                                                  CO - 10ppm

                                              Flue T - 470 degrees

    Non-NOX filter readings            O2 - 6%

                                                CO  - 25ppm

                                              Flue T - 470 degrees

    Most combustion trainers use 100ppm "As Measured" as the maximum CO in flue gas of vented appliances even though the ANSI standard is 400ppm "Air Free".  100ppm "As Measured" is 140ppm "Air Free" @ 6% O2 so it is well below industry standards.  The reason I use "As Measured" is because you must have an O2 reading to get "Air Free" and sometimes our O2 sensor might not be working or someone is using just a CO analyzer.

    Therefore the only time that the NOX filter might make some difference is when the CO reading is near 100ppm or 400ppm, which ever someone likes to reference.  Red Tagging is at 400ppm "Air Free" according to industry standards ANSI Z21.  The analyzer without the NOX filter will Red Tag equipment at a little lower ppm than one with one.  Equipment shouldn't be running anywhere near 400ppm CO anyway!

    Saying a meter with a NOX filter is more accurate is not necessarily true.  It depends on the calibration of the meter, the sensitivity of the sensor and the protocols of the person using it.  It have seen many NOX filtered analyzers read higher CO than ones without.  If the filter isn't built in I see no reason to spend additional money to add one.
  • SlimpickinsSlimpickins Member Posts: 314

    Well I was seriously thinking about buying a NOX filter so glad to hear that. Jim I took a combustion class years ago in Colorado Springs and didn't really gasp it at the time. Are you still putting on classes because I could use a refresher.
  • Jim DavisJim Davis Member Posts: 578
    Combustion Readings-Training

    I was just in Denver a couple of weeks before Christmas.  We probably won't be back there until fall.  ONly class out west will be in Cypress, CA in February.  We do have classes in Phoenix and sometimes Las Vegas.  Because of feedback from thousands of my students in the field, we keep fairly current with new equipment and problems along with the same ones that have existed forever.  The training is 10X better today than it was just a few years ago.
  • MikeyBMikeyB Member Posts: 696

    Jim, any plans for New York/Long Island training in the future? Thanks
  • Jim DavisJim Davis Member Posts: 578
    NY training

    We just cancelled a class in NY next week for no attendance.  I hope we can try again.
  • MikeyBMikeyB Member Posts: 696

    Please keep us posted Jim, Thank you 
This discussion has been closed.


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