baffled by NOx baffles
OK, I'm puzzled by high flue CO for no obvious reason, on two identical heaters. One gets used 3x less often due to the zones they handle, so is a lot less "worn out". Yet both units have identical numbers.
One thing -- both have those pesky California-special in-burner NOx baffles that lower flame temp. Could this explain higher CO? Manufacturer sells a version with baffles and one without, makes me think maybe baffles aren't so great....
Two identical nat gas heaters, Nordyne FG6TL-092N 92% dual-stage downflow units (92K BTU high, 55K BTU low) installed in 2004. Basics have been checked -- supply & manifold gas pressure, firing rate, inshot burners no air shutter to adjust, burners clean as a whistle & properly aligned, flame looks good & centered, heat exchangers not leaking & minimal corrosion, vent piping clean. Combustion blowers are new on both units, with new factory-spec restrictor orifice.
Both units have almost identical combustion analysis. Low Fire: CO 35ppm, CO2 3.4%, O2 14.8%, stack temp 105F. High Fire: CO 200ppm, CO2 5.8%, O2 10.7%, stack temp 113F (yes, high fire mode has been disabled permanently, due to safety concerns).
Do the baffles explain these CO numbers? Even at low fire, the 35ppm is about 120ppm air-free, not great....
There's way much excess air, can this explain the CO? But then at high fire there's less excess air, and CO is even worse.
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