24
3.3
GAS VALVE
The
“MURELLE 20/25 CE - 20 BF CE”
boilers are equip-
ped standard with a HONEYWELL V4600N gas valve
complete with a modulator screwed onto the pressure
regulator (Fig. 30).
The
“MURELLE IONO”
versions, without pilot burner, are
equipped standard with the SIT 837 TANDEM gas valve
(Fig. 30/a).
The
“MURELLE BF IONO”
versions, without pilot burner,
are equipped standard with the HONEYWELL VK4105M
gas valve (Fig. 30/b).
3.4
GAS VALVE ADJUSTMENT
Since all
“MURELLE”
versions are flame-modulation boi-
lers, they have the gas valve set at two pressure values:
maximum and minimum.
According to the type of gas burnt, these correspond to
the values given in Table 8. Calibration of the gas pressu-
res at the maximum and minimum values is done by SIME
in the factory. Consequently they should not be altered.
Only when you switch from one type of gas supply
(Natural gas) to another (L.P.G.) it is permitted to alter the
operating pressure.
It is essential that this operation be carried out exclu-
sively by authorized technical staff; otherwise, the
warranty will be rendered null and void.
When the gas pressures are to be reset, this must be
done following a set order: first the maximum pressure
and then the minimum for the models equipped with the
V4600N and 837 TANDEM gas valve and vice versa for
the models equipped with the VK4105 gas valve.
3.4.1
Maximum pressure adjustment V4600N
To set the maximum pressure, proceed as follows (Fig. 31):
– connect the pressure column or a pressure gauge to
the pressure inlet downstream of the gas valve;
– remove the retaining spring, completely withdraw the
modulator (4) and loosen the locking nut (2);
– tighten the screw (3) and set the knob of the D.H.W.
potentiometer to the maximum value (3, Fig. 32).
– ignite the boiler by operating the switch and open the
hot water tap;
– using a ø 12 spanner, turn the union (1) to arrive at the
maximum pressure value given in Table 8: to reduce
the pressure, turn the union counterclockwise; to
increase the pressure, turn it clockwise;
– once setted the pressure value tighten the locking nut
(2) and replace the modulator (4) in position;
– operate the main switch a number of times, keeping
the hot water tap open all the time, and check that the
pressure corresponds to the values given in Table 8.
KEY
1 Modulator
2 EV1-EV2 coil
3 Pressure inlet upstream
4 Pressure inlet downstream
KEY
1 Ignite/extinguish button
2 Modulator
3 Electric operator
4 Pilot burner adjusting screw
5 Pressure inlet downstream
6 Pressure inlet upstream
Fig. 30
Fig. 30/a
KEY
1 Modulator
2 EV1-EV2 coil
3 Pressure inlet downstream
4 Pressure inlet upstream
Fig. 30/b
