40
7217402.01 - en
INSTRUCTIONS FOR FITTERS
The authorised Technical Assistance Service can convert this boiler to natural gas (
G. 20
) or liquid gas (
G. 30, G. 31
).
17. GAS CONVERSION
C2) Adjustment to reduced heat output:
• disconnect the modulator feeding cable and unscrew the screw to reach the pressure setting corresponding to reduced
heat output (see table 1);
• reconnect the cable;
• fit the modulator cover and seal.
C3) Final checks
• attach the additional plate supplied with the transformer, specifying the type of gas and the calibration performed.
Carry out the following operations:
A) replace the main burner nozzles;
B) change the modulator voltage
C) new max. and min. calibration of the pressure regulator.
A) Replace the burner injectors
• carefully pull the burner off its seat;
• replace the burner injectors making sure to fully tighten
them to prevent gas leaks. Injector diameters are specified
in table 2.
Replacing the diaphragm nozzle
• remove the gas inlet hose (1 of Figure 8b);
• replace the diaphragm nozzle mounted on the gas valve
(2);
• put back the gas inlet hose.
B) Change the modulator voltage
•
set parameter
F02
according to the gas used, as descri-
bed in section
19.
C) Calibrate the pressure regulator
• connect the positive pressure test point of a differential
pressure gauge (possibly water-operated) to the gas valve
pressure test point (
Pb
) (Figure 8a). For models 240 i use
the pressure tap (3) in the gas inlet hose (figure 8b).
C1) Adjustment to nominal heat output:
• open the gas cock;
• press the button
(and set the boiler in winter mode
(section 3.2);
• open a hot water tap that can provide a flow rate of at
least 10 litres a minute or make sure there is maximum
heat demand;
• check that the boiler feeding dynamic pressure, as
measured at the inlet gas valve pressure test point (Pa)
(Figure 8a) is correct (
30 mbar
for
butane
gas,
37 mbar
for
propane
gas or
20 mbar
for
methane
gas);
• remove the modulator cover;
• adjust the tube brass screw to obtain the pressure settings
shown in table
1;
Valve SIT
mod. SIGMA 845
Figure 8a
9912221500
Pc
Pb
Pa
0206_0501
Figure 8b