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Combustion analyzer

Dan C.
Dan C. Member Posts: 248
I sent my Testo 320 in for service because it was giving me what I thought to be very low CO readings. I got it back and the first time I used it, I was getting 0 PPM CO. I set up my Bacharach Fyrite in the same flue and was getting 26 PPM. I called Testo and they told me that my unit is accurate and that they use some different kind of Nox filter and anyone that doesn't use the same type that they use is giving inaccurate readings for CO. He specifically mentioned Bacharach and UEI. He also refereed me to this video. https://www.youtube.com/watch?v=VBXPUv2Nd_Q . I have attached a picture of the two side by side. I am just wondering if this is true. I would be surprised if Bacharach and UEI are selling analyzers that aren't giving correct CO readings. I like both units but I really want my test results to be accurate. Has anyone else heard of this? Thoughts on it?


  • adambnyc
    adambnyc Member Posts: 260
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    I had a similar issue w/ my Bacharach Insight on oil...was getting no CO readings vs. my UEI. It was sent back to the factory and is 'working fine'. It is the nox filter. Without one, I guess the products of combustion in fuel oil (nox) were tricking the analyzer into thinking it was CO.
    If you can get 2 identical units into the same flue pipe and check one against the other, that may help with making sure yours is working correctly.

    There was an error rendering this rich post.

  • captainco
    captainco Member Posts: 796
    The odds of having that concentration of NOX in the flue gas is unlikely. If 10 ppm of CO is going to mess up your diagnostics you are following some weird protocols.

    Having used Bacharach, Testo, UEI and a few others, I find that the units with NOX filters read just as high or higher about 50% of the time.

    I am pretty sure if you put 12 Testo units in a flue you will get 12 different CO readings as you would with any analyzer.

    The worst thing that can happen with an analyzer without a NOX filter is that you may make a piece of equipment a little safer.

    Talk about a really inaccurate reading, lets talk about the stupid "Air Free" calculation.
  • GW
    GW Member Posts: 4,700
    that's pretty annoying---zero?? I want to see something!
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
  • Dan C.
    Dan C. Member Posts: 248
    edited January 2018
    Is it likely that a natural gas boiler would have 0 ppm CO? Even 1 or 2 seems very low to me. I really like the Testo but if it’s not accurate I don’t want to use it.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,515
    I agree with CaptainCO about the different readings from different analyzers. If you think about how small a Part per Million or PPM is, Consider this
    One PPM is
    1 day in 2,739 years
    1 inch in 16 miles
    1 square foot in 23 acres
    Ray Wohlfarth
    Boiler Lessons