interpreting comb analyzer results

Munchkin doesn't go to specified CO range

Hello...I'm a homeowner with some general technical expertise but no training in heating. Our Munchkin condensate drain stopped up last year (its third year of operation) and the insulating disks fell apart from being soaked. Also we have had recurring problems with the flame sensor needing to be cleaned.

I figured I would borrow a comb analyzer and try to see if the deposits are forming due to the boiler being out of spec. (Our local service people don't use comb analyzers, and it was not originally set up with one.)

The manual gives CO and CO2 ranges for low fire (0-20ppm, 8.5-9.5%) and high fire (80-135ppm, 8.5-9.5%). There is no problem bringing the boiler this into range for high fire. But at low fire, I cannot do it. The lowest I can go is CO 55ppm, much higher than the manual's maximum of 20ppm; here I have CO2 10%, higher than the maximum of 9.5%. The CO value remains flat for about one turn either way from this setting, and then begins to go up on both sides. I left it at this setting (on high fire I have CO 90ppm, CO2 9.2ppm, which is well within the specified range of 80-135ppm/8.5-9.5%.)

(It doesn't help that the throttle screw has about 3/4 turn backlash!)

Is this a sign of a problem? Too much CO = incomplete consumption = carbon deposits? Or is the difference between 20ppm and 55ppm a completely trivial matter? By the way the setting is basically where it was before I started adjusting it.

[The analyzer is a UEI C75. I know it is not really a professional-quality device but I don't really have a choice.]

No analyser ???

Years ago (probaly in the early seventies) I attended a Kewaunee Boiler/Burner school for setting up large commercial steam and hot water boilers w/ combination gas/oil burners.

I distinctly remeber the instructors words of wisdom....."In Germany and other parts of Europe, homeowners have combustion analysers and smoke samplers to insure proper firing of their heating equipment" end quote.

I am probaly going to catch a little flack here but what the heck?

How can any HVAC or hydronic heating service provider call themselve's professionals if they do not have the proper tools and equipment to set burners to mfg's settings or industry parameters?

This never could be done properly by sight or color and today with all the sophisticated equipment out there it should be a requirement with all equipment installed or serviced.

These analysers are no longer that expensive and believe it or not they work!!!


Rich K.


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