39
+
+
3
12
1
P1
2
P3
4
51
INS
TALLER
US
ER
MAINTEN
AN
CE TECHNI
CI
AN
3.8 CHECKS FOLLOWING CONVERSION TO ANOTHER
TYPE OF GAS.
After making sure that conversion was carried out with a nozzle
of suitable diameter for the type of gas used and the settings are
made at the correct pressure, check that the burner flame is not
too high or low and is stable (does not detach from burner);
All boiler adjustment operations must be carried out
by a qualified company.
3.9 CALIBRATION OF NUMBER OF FAN REVS.
ATTENTION:
verification and calibration is necessary,
in the case of transformation to other
types of gas, in the extraordinary maintenance
phase with replacement of the PCB air/gas cir-
cuit components or in the case of installations
with flue extraction systems, with horizontal
concentric pipe measuring more than 1 metre.
The boiler heat output is correlated to the length of the air intake
and flue exhaust pipes. This decreases with the increase of pipe
length. The boiler leaves the factory adjusted for minimum pipe
length (1m). It is therefore necessary, especially in the case of
maximum pipe extension, to check the ∆p gas values after at least 5
minutes of the burner operating at nominal heat output, when the
temperatures of the intake air and exhaust flue gas have stabilised.
Adjust the nominal and minimum heat output in the domestic
hot water and central heating modes according to the values in
the table (Par. 4.1) using the differential manometers connected
to the ∆p gas pressure points (16 and 17 Fig. 35).
Enter the configurations menu and regulate the following param-
eters (Par. 3.11):
- minimum DHW power output;
- maximum DHW power output;
- minimum central heating output;
- maximum central heating output;
- Ignition power.
3.10 CO
2
ADJUSTMENT.
Attention:
the CO
2
verification operations must be carried out
with the casing mounted, while the gas valve calibration operations
must be carried out with the casing open and disconnecting the
boiler from the power supply.
To have an exact value of CO
2
in the flue gases, the technician must
insert the sampling probe to the bottom of the sample point, then
check that the CO
2
value is that specified in the following tables
(Ref. Par. 4.2) (using maximum tolerance of ± 2%), otherwise
change the value described as follows:
- Calibration of the minimum CO
2
(minimum central heating
power).
Enter the chimney sweep phase without withdrawing domestic
hot water and take the selector switches to minimum (turn them
in an anti-clockwise direction until “0” is seen on the display).
Adjust the screw (3 Fig. 39) (Off-Set adjuster). To increase the
CO
2
value, turn the adjustment screw (3) in a clockwise direction
and vice versa to decrease it.
- Calibration of the maximum CO
2
(nominal central heating
power).
On completion of the adjustment of the minimum CO
2
keeping
the chimney sweep function active, take the heating selector
switch to maximum (turn it in a clockwise direction until “99”
is seen on the display).
Adjust the screw (12 Fig. 39) (gas flow rate regulator). To increase
the CO
2
value, turn the adjustment screw (12) in an anti-clock-
wise direction and vice versa to decrease it.
At every adjustment variation on the screw 12 it is necessary
to wait for the boiler to stabilise itself at the value set (about 30
sec.).
Key:
1 - Gas valve inlet pressure point
2 - Gas valve outlet pressure point
3 - Off/Set adjustment screw
12 - Outlet gas flow rate regulator
Gas Valve SIT 848
