13
4 - AIR PRESSURE SWITCH (A)
Adjust the air pressure switch after having per-
formed all other burner adjustments with the air
pressure switch set to the start of the scale (A).
With the burner working at MIN output, insert a
combustion analyser in the stack, slowly close
the suction inlet of the fan (for example, with
cardboard) until the CO value does not exceed
100 ppm.
Then slowly turn the appropriate knob clockwise
until the burner reaches the lockout position.
Check the indication of the arrow pointing
upwards on the graduated scale (A). Turn the
knob clockwise again, until the value shown on
the graduated scale corresponds with the arrow
pointing downwards (A), and so recovering the
hysteresis of the pressure switch (shown by the
white mark on a blue background, between the
two arrows).
Now check the correct start-up of the burner.
If the burner locks out again, turn the knob anti-
clockwise a little bit more.
The incorporated air pressure switch can work
in a "differential" way if connected with two
pipes; see1)(A). If a strong depression in the
combustion chamber during the pre-purging
phase does not allow the air pressure switch to
commute, commutation can be obtained by
applying a second tube between the air pres-
sure switch and the suction inlet of the fan. In
this way, the pressure switch will work in differ-
ential mode.
5 - MINIMUM GAS PRESSURE SWITCH (B)
With the burner operating at MAX output,
increase adjustment pressure by slowly turning
the relative knob clockwise until the burner locks
out.
Then turn the knob anti-clockwise by 5mbar and
repeat burner starting to ensure it is uniform.
If the burner locks out again, turn the knob anti-
clockwise again by 1mbar.
FLAME PRESENCE CHECK (C)
The burner is fitted with an ionisation system
which ensures that a flame is present. The mini-
mum current for control box operation is 6 µA.
The burner provides a much higher current, so
controls are not normally required. However, if it
is necessary to measure the ionisation current,
disconnect the plug-socket 24)(A)p.4 on the ion-
isation probe cable and insert a direct current
microammeter with a base scale of 100 µA.
Carefully check polarities.
1 kPa = 10 mbar
(A)
(C)
AIR PRESSURE SWITCH 4)(A)p. 4
MINIMUM GAS PRESSURE SWITCH
(B)
1)
2)
RMG/M
10
D3842
D3843
µA
D3855
D3951
