A Qualified Service Engineer may adapt this boiler to operate with natural gas (G. 0) or with liquid gas (G. 31).
A Qualified Service Engineer may adapt this boiler to operate with natural gas (G. 0) or with liquid gas (G. 31).
The procedure for calibrating the pressure regulator may vary according to the type of gas valve fitted (HONEYWELL or
SIT; see figure 12).
Carry out the following operations 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-
cified 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" fitting 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 flow
rate or ensure that maximum heating requirements are
set;
• remove the modulator cover;
• adjust the tube brass screw (a) Fig. 13 to obtain the pres-
sure 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);
c) adjustment to reduced heat output
• disconnect the modulator feeding cable and unscrew the
(b) Fig. 13 screw to reach the pressure setting correspon-
ding to reduced heat output (see table 1);
• connect the cable again;
• fit the modulator cover and seal.
c3) Final checks
• apply the additional dataplate, specifying the type of gas
and settings applied.
instructions pertaininG to the
19. GaS CHanGE MOdalItIES
);
instaLLer
14
honeywell valve
mod. VK 4105 M
pb
pa
sit valve
mod. siGMa 845
pc
pb
pa
Figure 1
pc
94.674. - GB