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6.6
Pressure switch adjustment
6.6.1
Air pressure switch
Adjust the air pressure switch after performing all other burner
adjustments with the air pressure switch set to the start of the
scale (Fig. 29).
With the burner operating in 1st stage, increase adjustment
pressure by slowly turning the relevant knob clockwise until the
burner locks out.
Then turn the knob anti-clockwise by about 20% of the set point
and repeat burner starting to ensure it is correct.
If the burner locks out again, turn the knob slightly anticlockwise.
As a rule, the air pressure switch must limit the CO
in the fumes to less than 1% (10,000 ppm).
To check this, insert a combustion analyser into
the chimney, slowly close the fan suction inlet (for
ATTENTION
example with cardboard) and check that the
burner locks out, before the CO in the fumes
exceeds 1%.
The incorporated air pressure switch can work in a 'differential'
mode if connected with two pipes.
If a strong depression in the combustion chamber during the pre-
purging phase does not allow the air pressure switch to switch,
this can be obtained by applying a second tube between the air
pressure switch and the suction inlet of the fan.
In this way, the pressure switch will work in differential mode.
The use of the air pressure switch with differential
operation is allowed only in industrial applications
and where rules enable the air pressure switch to
control only fan operation without any reference to
ATTENTION
CO limit.
D3951
Start-up, calibration and operation of the burner
D3842
Fig. 29
6.6.2
Gas minimum pressure switch
Adjust the minimum gas pressure switch after performing all the
other burner adjustments with the pressure switch set to the start
of the scale (Fig. 30).
With the burner operating in 2nd stage, increase adjustment
pressure by slowly turning the relevant knob clockwise until the
burner stops.
Then turn the knob anticlockwise by 0.2 kPa (2 mbar) and repeat
burner start-up to ensure it is operating regularly.
If the burner locks out again, turn the knob again anticlockwise by
0.1 kPa (1 mbar).
1 kPa = 10 mbar
ATTENTION
6.6.3
Flame presence check
The burner is fitted with an ionisation system to check that a
flame is present. The minimum current required for the control
box operation is 6 A.
The burner supplies a significantly higher current value, so that
no check is usually needed.
However, if it is necessary to measure the ionisation current,
disconnect the plug-socket 8)(Fig. 4 on page 12) on the
ionisation probe cable and insert a direct current microammeter
with a base scale of 100 A.
Carefully check polarities.
D3843
27
GB
D3855
Fig. 30
µA
10
RMG
Fig. 31
20159324
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