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Testo NOx filtering

TomM Posts: 233
had a bacharach 125, and it took a crap.

bought a Testo 310 (budget model)

To my surprise, the same gas boiler which read 60ppm CO with the bacharach, read 6 ppm max with the new Testo with NOx filters. 

Holy crap is that legit? 

Will call Testo tomorrow, but figured i'd make a post anyway.

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  • MikeyB
    MikeyB Member Posts: 696

    I put the NOX filter on my Frite Insight and i got a reading of 3ppm CO air free (on my own oil burner), the day before I put the NOX on i got a reading of 69ppm CO air free, it sure does scrub the gas, I emailed Timmie about that and he gave me a great explanition, but dont have it handy, and Testo also wrote a paper on the purpose of using a NOX filter, search for it and you will find it, good stuff
  • MikeyB
    MikeyB Member Posts: 696

    Found it
  • Jim Davis_3
    Jim Davis_3 Member Posts: 578
    NOX flltering

    For many years I used a combustion analzyer that measured NOX.  NOX is a by-product of efficient combustion.  The hotter the flame the more NOX you make.  Testing many commercial and industrial appliance, gas and oil, I never saw a NOX reading above 120ppm.  This is with O2 readings around 2%-3%.  However, as the O2 increases and the flame gets cooler the NOX goes down to 20-ppm to 60-ppm.  This should cause about a maximum of 10-ppm to 30-ppm higher CO reading.  With 100ppm being the maximum we teach in flue gas samples for all vented appliances, if you were readings 100ppm of CO with an analzyer that did not have a NOX filter, the CO might only be 70ppm.  Not really going to mess anything up.  You will end up just slightly safer.

    The problem I have seen over the years is when I put 2 analyzers in the flue that have NOX filters and they don't match either.  Many times I have seen an analzyer read higher CO with a NOX filter than without one.  These readings were taken with units that were just checked for calibration. 

    I still question whether or not the NOX filter de-sensitizes the CO sensor from CO.  Something to also consider is that all CO sensors have different sensitivities in flue gas.  It is almost impossible to get two different analzyers to read the same CO when testing.

    Whatever analyzer you have should be accurate, dependable and repeatable to itself, not any other analzyer.  O2 & temperature are the only readings that will ever be close from one to the other.  Trust whatever analyzer you have and don't worry what somebody else's might be reading.  As long as it responds to CO it is good to go.
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