7 Flue gas measurement
7.2.2 Causes associated with the measuring device
Measuring cells are not in order:
Pay attention to the display when calibrating. The function can be checked under “Service”.
Measuring device leaks:
All hose connections and condensate tanks must be sealed. Check by keeping the intake opening closed briefly. The
pump noise must be clearly muffled.
Measured gas flow is insufficient (intake path is blocked or pump is defective):
Recognizable if there is no suction on the intake opening and the measured value only changes extremely slowly.
A cause can be a water drop in the pump valve (device must dry out for an entire day with hoses disconnected). Never
blow through the hoses with the device connected! (This will render pump and draught measurement defective).
Calibration executed in air that is not clean:
Often the CO and CO
2 values are slightly increased on the floor of the boiler room. Measurement device filters and
hoses that are blocked with soot also give off CO and CO
2 when they are warm.
7.2.3 Causes associated with the boiler
Secondary air discharge in the combustion chamber:
The boiler door and the ash box must be sealed. For ash removal systems, fill the ash worm holes in the ash box
with ash and press lightly.
Entry of secondary air between flue gas collector and measurement bore:
The measurement bore should be 50 cm behind the induced draught fan. The flue gas path (maintenance cover,
shackle, muffs) must be completely sealed. If there is a strong chimney draught, air can enter at the shaft of the
induced draught fan. If in doubt drill a second bore in the smoke pipe box and compare the CO
2 value.
Undesired fuels increase CO
2 and CO values:
With new boilers there is an outgassing of paint, lubricating grease, and the binders in the insulating materials of the
boiler doors. With old boilers existing soot coatings or unburned content in the ash can also combust.
7.2.4 Causes for the measurement sensor
The following faults also occur when the measurement has been absolutely correctly executed. However they are
negligible for boiler adjustment:
Measurement tolerances of the device (MRU Nova H8):
Temperature: ± 2 °C
O
2
content ± 02 % by volume
CO content: ± 25 ppm
Draught: ± 0.03 mbar
Standard values for the conversion in the measurement device:
The measurement device calculates the other values from the measured values cited above, on the display panel.
In this process standard values are assumed for fuel characteristic values (calorific value, water content, chemical
analysis that do not agree with the characteristics of the fuel used ( emission values in mg/MJ, efficiency).
MA-Easyfire 10.2008_EN.indd 77MA-Easyfire 10.2008_EN.indd 77 30.03.2009 13:30:12 Uhr30.03.2009 13:30:12 Uhr
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