82
71.03982.03 - EN
INSTALLATION INSTRUCTIONS
19. GAS CONVERSION
The authorised Technical Assistance Service can convert this boiler to natural gas (
G. 20
) or liquid gas (
G.31
).
Carry out the following operations:
A) replace the nozzles of the main burner and the gas diaphragm (if itted);
B) new max. and min. calibration of the pressure regulator.
A) Replace the burner nozzles
• carefully pull the main burner off its seat;
• replace the main burner nozzles making sure to fully tighten them to prevent gas leaks. Nozzle diameters are speciied
in table 2.
B) 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 10). Only for models with sealed chambers, connect the negative pressure test point of
the manometer to a “T” itting in order to join the boiler adjustment outlet, the gas valve adjusting outlet (Pc) and the
pressure gauge. (The same measurement can be made by connecting the pressure gauge to the pressure test point
(
Pb
) after removing the front panel of the sealed chamber);
Measuring burner pressure using methods other than those described could lead to incorrect results as the low pressure
created by the fan in the sealed chamber would not be taken into account.
B1) Adjustment to nominal heat output:
• open the gas tap and switch the boiler to the Winter mode;
• open a hot water tap that can provide a low rate of at least 10 litres a minute or make sure there is maximum heat
demand;
• remove the modulator cover;
• adjust the tube brass screw (a) until the pressure values shown in table 1 are obtained;
make sure that the dynamic inlet pressure of the boiler, measured at the gas valve pressure test point (Pa) (Figure 10) is
correct (37 mbar for propane or 20 mbar for natural gas).
B2) Adjustment to reduced heat output:
• disconnect the modulator power cable and unscrew the screw (b) until a pressure value corresponding to reduced heat
output is achieved (see tab. 1);
• reconnect the cable;
• mount the modulator cover and seal.
B3) Final checks
• attach the additional plate supplied with the transformer, specifying the type of gas and the calibration performed.
Figure 10
gas valve
mod. SIGMA 845
b
a
0605_1502
Figure 11
CG_2273 / 1008_2602
gas diaphragm
ATTENTION
If the natural gas inlet pressure is too low (less than 17 mbar) remove the gas diaphragm installed over the gas valve (ig.
10) and set parameter
F02=00
on the electronic board (§21).
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