Technical data

924.674.3 - GBINSTRUCTIONS PERTAINING TO THE INSTALLER

A Qualied Service Engineer may adapt this boiler to operate with natural gas (G. 20) or with liquid gas (G. 31).

The procedure for calibrating the pressure regulator may vary according to the type of gas valve tted (

HONEY WELL or

SIT; see gure 12).

Carry out the following ope rations in the given sequence:

A) substitute the main burner injectors;

B) change the modulator voltage;

C) proceed with a new max. and min. setting of the pressure adjusting device.

A) Substitute the main burner injectors

• carefully pull the main burner off its seat;

• substitute the main burner injectors and make sure you tighten them to avoid leakage. The nozzle diameters are spe-

cied in table 2.

B) Change the modulator voltage

• remove the 2 screws securing the control board cover and hinge it upward;

• set the jumper or the switch, according to the type of gas used, as described in the chapter 22.

C) Pressure adjusting device setting

• connect the positive pressure test point of a differential (possibly water-operated) manometer to the gas valve pressure

test point (Pb) (Figure 12); connect, for sealed chamber models only, the negative pressure test point of the manometer

to a “T” tting in order to join the boiler adjusting outlet, the gas valve adjusting outlet (

Pc) and the manometer. (The

same measurement can be carried out by connecting the manometer to the pressure test point (

Pb) after removing the

sealed chamber front panel);

If you measure the pressure of burners in a different way you may obtain an altered result in that the low pressure created

in the sealed chamber by the fan would not be taken into account.

C1) Adjustment to rated output

• open the gas tap and rotate knob (Figure 12) to set the boiler to the Winter setting ( );

• open a hot water tap to reach a minimum 10 l/minute ow rate or ensure that maximum heating requirements are set;

• remove the modulator cover;

• adjust the tube brass screw (a) Fig. 13 to obtain the pressure settings shown at table 1;

• check that boiler feeding dynamic pressure, as measured at the inlet gas valve pressure test point (Pa) (Figure 12) is

correct (37 mbar for LPG gas (G.31), 20 mbar for natural gas);

C2) Adjustment to reduced heat output

• disconnect the modulator feeding cable and unscrew the (b) Fig. 13 screw to reach the pressure setting corresponding

to reduced heat output (see table 1);

• connect the cable again;

• t the modulator cover and seal.

C3) Final checks

• apply the additional dataplate, specifying the type of gas and settings applied.

19. GaS CHanGE MOdalItIES

Figure 12

SIT valve - mod. SIGMA 845 Honeywell valve - mod. VK 4105 M

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