3
CHECKING AND REGULATING COMBUSTION
In order to obtain optimum combustion efficiency and to safeguard the environment, we recommend to check,
and regulate combustion using the appropriate instruments.
The most important levels to be checked are:
●
CO
2
. The level of CO
2
indicates the excess of air percentage during combustion; if the quantity of air is
increased, then the CO
2
level decreases, while a decrease in combustion air leads to an increase in CO
2
.
Acceptable values would be between 8.5 and 10% NATURAL GAS , 11-12% B/P.
●
CO. This indicates the presence of unburnt gas; CO, as well as lowering the combustion efficiency, is also a danger,
being a poisonous gas. The presence of CO is thus an indication of imperfect combustion, and is usually a sign that
there is a lack of air during combustion. Maximum acceptable value is CO = 0.1% volume.
●
Flue gas temperature. This represents the loss of heat through the chimney; the higher is the temperature,
the greater is the loss of heat and the lower is the combustion efficiency. If the temperature is too high, then
it is necessary to decrease the amount of gas burnt. Acceptable temperature levels range between 160°
and 220°C.
IONISATION CURRENT
When calibration is completed and the combustion tests have been conducted, check that the control electro-
de is positioned correctly. This is accertained by measuring the ionisation current. Use a microamperometer
with a scale of 100 µA, and connect it in series to the electrode. The minimum value of the current should
be 30 µA and relatively stable.
Normally the flame monitoring circuit is insensitive to the negative influences of the ignition spark on the
ionisation current. If the disturbances of the ignition spark on the ionisation current are excessive, it will
be necessary to invert the polarity of the electrical connection of the starting transformer primary and/or
verify the placement of the starting electrode in relation to the ionisation electrode.
N.B. When the burner is started up, ensure that there are no leaks from the gas circuit.
N.B. Existing regulations in some countries may require a regulation different from that
indicated, as well as compliance with other parameters.
PROLONGED SHUT-DOWN
Should the burner be inactive for a long period of time, turn off the gas cock and disconnect power from the unit.
CHECKING IONIZATION CURRENT
The minimum value of 30 µA should be observed,
and large oscillations are to be avoided.
MICROAMPEREMETER CONNECTION
MPE
1
∝
A
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