26
The boiler can be converted to use either methane (natural) gas (G20)
or L.P.G. (G30 - G31) by an Authorised Service Centre.
The operations that must be performed are the following:
1. Replace the jets on the main burner (see table in section 4);
2. Adjust the maximum and minimum thermal capacity values for the boiler
(see table in section 4 and 4.2 Adjusting the Gas Pressures);
3. Adjust the maximum thermal power setting;
4. Adjust the soft-light feature
(see table below for recommended
pressure);
5. Adjust the ignition delay feature for the heating system by adjusting the
potentiometer as shown in
FIG. 4.1 (can be set from 0 to 2 mins.).
4.1 CHANGING THE
TYPE OF GAS
4. GAS ADJUSTMENTS
CATEGORY
II2H3+
Model
Microcombi
Methane Gas
G20
Liquid
Butane Gas
G30
Liquid
Propane Gas
G31
Recommended
Soft-light
Pressure
(mbar)
23 MFFI 8.0 16.0 16.0
27 MFFI 6.7 12 12
Model CATEGORY II2H3+ Methane Gas
G20
Liquid Butane Gas
G30
Liquid Propane Gas
G31
23 MFFI
27 MFFI
Lower Wobbe Index (15°C;1013mbar) MJ/m
3
h
Nominal Delivery Pressure mbar
Minimum Delivery Pressure mbar
45.67
20
20
80.58
29
28
80.58
37
36
23 MFFI Main Burner: n. 12 jets (ø) mm
Consumption (15°C; 1013mbar) m
3
/h
Consumption (15°C; 1013mbar) Kg/h
Gas Burner Pressure
max - min mbar
1.30
2.78
----
11.0 - 2.0
0.77
----
2.02
27.7 - 6.0
0.77
----
2.00
35.5 - 7.3
27 MFFI Main Burner: n. 13 jets (ø) mm
Consumption (15°C; 1013mbar) m
3
/h
Consumption (15°C; 1013mbar) Kg/h
Gas Burner Pressure
max - min mbar
1.3
3.10 - 1.16
---
12.2 - 1.7
0.77
---
2.31 - 0.87
27.8 - 5
0.77
---
2.27 - 0.85
35.8 - 5.3
4.2 ADJUSTING THE GAS PRESSURES (SIT SIGMA)
Setting the minimum and the maximum power of the boiler
1. Check that the supply pressure and dynamic pressure to the gas valve is
a minimum of 20 mbar for natural gas.
2. To do this, loosen the screw “A”.
Fit the pipe of the pressure gauge to the inlet pressure connection of the
gas valve “B” and check for the correct standing pressure, then operate
the appliance and check for the correct working pressure.
When you have completed this operation, replace the screw “A” securely
into its housing to seal off the gas (check for tightness).
3. To check the pressure supplied by the gas valve to the burner, loosen the
screw “C”. Fit the pipe of the pressure gauge to the pressure outlet test
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