42
UK
CHECKING CONTROL BOX IONIZATION CURRENT
MICROAMPEREMETER CONNECTION
The minimum value of 3 μA should be
observed, and large oscillations are to be
avoided.
CHECKING 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 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: 8.5-10% METHANE, 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. Accep-
table temperature levels range between 160°C and 220°C.
NOTE: Certain countries may have different regulations, and thus different admissible levels
from those given above.
START UP
Check the position of the ignition electrode tips and the position of the control electrode.
Check the correct operation of the gas and air pressure switches. When the thermostatic line
and the gas pressure switch close the control box gives consent for the motor to be started.
During this period the control box conducts a self-test of its correct working order. If the test is
positive then the cycle continues and at the end of the pre-purge period (TPR - combustion
chamber purge) the consent is given to the transformer for the spark at the electrodes, and
to the solenoid valve for opening. Within the safety time (TS) flame stabilization should occur,
otherwise the system goes in lock-out mode.
PROLONGED SWITCHING OFF
If the burner should remain inactive at length close the gas cock and remove the electrical
current from the appliance.
Summary of Contents for EM 16-E
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