28
Adjustment of Maximum and Minimum pressure on
the modulator
NOMINAL OUTPUT (Maximum)
• Open the gas cock and rotate knob (1) to set the boiler to Winter
position and wait for the boiler lighting.
• Check that boiler feeding dynamic pressure, as measured at the inlet
gas valve pressure intake (ref. 2 fi gure 11) is correct (30 mbar for
butane, 37 mbar for propane, 20 mbar for natural gas).
• Remove the modulator plastic cap, rotate the brass nut until you reach
the pressure setting corresponding to the nominal heat output (see
table III, according to the model of boiler).
REDUCED OUTPUT (Minimum)
• Disconnect a modulator cable and unscrew the modulator red screw
to reach the pressure setting corresponding to the reduced heat output
(see table IV, according to the model of boiler).
• Then connect the cable again, fi t the modular plastic cap and seal the
fi xing screw.
Adjustment of the Central Heating heat output
It is possible to regulate the Central Heating heat output to the real
needs of the system. The following instructions will permit you a correct
adjustment:
• Rotate the switch (1) to Winter position, wait for the boiler’s lighting
(signal of Heating operation (6) switched on).
• Reach the electrical box as described in paragraph 5.1: “Access to
the power supply terminal block” and rotate the pressure setting P3
MAX. R of the boiler PCB, to reach the pressure setting at the burner
as indicated in tables IV according to the output and the model of
boiler.
Final checks
• Close the control panel.
• Take off the manometers and close the pressure intakes.
• Apply the additional data-plate, specifying the type of gas and setting
applied.
• Reassemble the frontal door.
14. Gas conversion
A qualifi ed Service Engineer may adapt this boiler to operate with natural
gas (G20) or with liquid gas (G30, G31).
To operate the boilers with a gas different from the one for which the
boiler is set, it is necessary to make the following operations:
• Open and remove the frontal door of the boiler.
• Connect two manometers (water manometer, if possible) to the pres-
sure intake (ref. 1 and 2, fi gure 11) of the gas valve, after loosing the
respective screws.
Replacement of the burner’s injectors
• Remove the front box of the sealed chamber.
• Replace the burner’s injectors making sure you tighten them, using
also the copper washer, to avoid any leakage. Refer to Table III for
the injectors’ diameter, depending on the type of gas.
• Fit the front box of the sealed chamber back on.
Modulator voltage change
• Reach the inside of the electrical box as described on paragraph 5.1:
“Access to the power supply terminal block”.
• Position the respective switch depending on the type of gas (see
paragraph 13).
KEY
1. Pressure intake –
Outlet
2. Pressure intake – Inlet
3. Solenoid valve
4. Modulator with Min-
Max adjustment
Figure 11:
SIT SIGMA 845 gas valve
9912221500
2
1
4
3
Adjustment of the
maximum
Adjustment of the
minimum
Burner’s injector
9505080301
