14
AIR PRESSURE SWITCH (A)
Adjust the air pressure switch after having performed all
other burner adjustments with the air pressure switch set
to the start of the scale (A).
With the burner operating at min. output, increase adjust-
ment pressure by slowly turning the relative dial clock-
wise until the burner locks out.
Then turn the dial 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 dial anti-clockwise
a little bit more.
Attention:
As a rule, the air pressure switch must prevent the forma-
tion of CO.
To check this, insert a combustion analyser into the
chimney, slowly close the fan suction inlet (for example
with cardboard) and check that the burner locks out,
before the CO in the fumes exceeds 400 ppm.
The air pressure switch may operate in "differential"
operation in two pipe system. If a negative pressure in
the combustion chamber during pre-purging prevents
the air pressure switch from switching, switching may be
obtained by fitting a second pipe between the air pres-
sure switch and the suction inlet of the fan. In such a
manner the air pressure switch operates as differential
pressure switch.
HIGH GAS PRESSURE SWITCH (B)
Adjust the high gas pressure switch after having per-
formed all other burner adjustments with the maximum
gas pressure switch set to the end of the scale (B).
With the burner operating at MAX output, reduce the
adjustment pressure by slowly turning the adjustment
dial anticlockwise until the burner locks out.
Then turn the dial clockwise by 0.8” WC and repeat
burner firing.
If the burner locks out again, turn the dial again clock-
wise by 0.4” WC.
LOW GAS PRESSURE SWITCH (C)
Adjust the low gas pressure switch after having per-
formed all the other burner adjustments with the pressure
switch set at the start of the scale (C).
With the burner operating at MAX output, increase ad-
justment pressure by slowly turning the relative dial
clockwise until the burner locks out.
Then turn the dial anti-clockwise by 0.8” WC and repeat
burner starting to ensure it is uniform.
If the burner locks out again, turn the dial anti-clockwise
again by 0.4” WC.
FLAME PRESENT CHECK (D)
The burner is fitted with an ionisation (flame rod) system
which ensures that a flame is present. The minimum
current for reliable operation is 6
μ
A (see manufacturers
documentation). The burner provides a much higher cur-
rent, so that controls are not normally required. How-
ever, if it is necessary to measure the ionisation current,
disconnect the plug-socket 6)(A)p.5 on the ionisation
probe cable and insert a direct current microamperome-
ter with a base scale of 100
μ
A. Carefully check polari-
ties.
(A)
AIR PRESSURE SWITCH
(B)
HIGH GAS PRESSURE SWITCH
(C)
LOW GAS PRESSURE SWITCH
(D)
D2548
D2547
D2547
D1565
DA
