26
3.4.6
Maximum pressure adjustment VK4105M
To set the maximum pressure, proceed as follows (Fig.
31/b):
– set the knob of the D.H.W. potentiometer to the maxi-
mum value (3, Fig. 32);
– ignite the boiler by operating the switch and open the
D.H.W. tap at a high flow rate;
– using a ø 7 spanner turn the nut (3, Fig. 31/b) to arrive
at the maximum pressure value given in Table 8: to
reduce the pressure, turn the screw counterclockwise;
to increase the pressure, turn it clockwise;
– operate the main switch a number of times, keeping
the D.H.W. tap open all the time, and check that the
pressure corresponds to the values given in Table 8;
3.5
ADJUSTMENT OF HEAT OUTPUT
FOR HEATING
To adjust boiler heat output for heating purposes, i.e.,
modifying the setting made at the factory, which is
approximately 16 kW in the
“20”
vers. , 18 kW in the
“25
CE - 25 CE IONO”
vers. and 19 kW in the
“25 BF CE
IONO”
vers. use a screwdriver to adjust the heating heat
output trimmer (2, Fig. 32).
To increase working pressure, turn the trimmer clockwise
(towards the + sign); to reduce pressure, turn the trimmer
counterclockwise (towards the – sign).
When the temperature read by the sensor corresponds to
the value selected on the potentiometer, the boiler will
already be at minimum burner flame. At this point, the
potentiometer will cause the burner to go out. To facilita-
te the operations of adjusting heat output, see the pres-
sure/heat output diagrams for natural gas (methane) and
butane or propane gas, shown in figs. 33 and 34.
3.6
PILOT BURNER ADJUSTMENT
The
“MURELLE 20 CE - 20 BF CE”
versions are equip-
ped with pilot flame which, provided it is properly adju-
sted, should envelop the end portion of the thermocouple
over a length of 8 to 10 mm. Adjustment is made by tur-
ning the adjusting screw (4, Fig. 30):
– to reduce gas flow, turn the screw clockwise;
– to increase gas flow, turn the screw counterclockwise.
3.7
CONVERSION TO DIFFERENT GAS
To convert to butane gas (G30) or propane gas (G31),
first replace the main nozzles and the pilot nozzle
(
“MURELLE 20 CE - 20 BF CE”
versions).
Proceed as follows (Fig. 35):
– close the gas cock;
– in the
“MURELLE 20 CE - 20 BF CE”
versions, unscrew
the interrupted thermocouple (6) and the pilot feed pipe
connection (3), and remove the ignition electrode (5);
25
20
15
10
8,1 (7.000)
11,6 (10.000)
17,4 (15.000)
23,2 (20.000)
POTENZA TERMICA kW (kcal/h)
30
5
29,1 (25.000)
3.5.2
Pressure/heat output diagram for
L.P.G. gas (G30)
HEAT OUTPUT kW (kcal/h)
NOZZLE PRESSURE mbar
Fig. 34
11
10
9
8
7
6
5
4
3
2
1
8,1 (7.000)
11,6 (10.000)
17,4 (15.000)
23,2 (20.000)
POTENZA TERMICA kW (kcal/h)
29,1 (25.000)
3.5.1
Pressure/heat output diagram for natural gas
HEAT OUTPUT kW (kcal/h)
NOZZLE PRESSURE mbar
Fig. 33
KEY
1 Heating
potentiometer
2 Trimmer
3 D.H.W.
potentiometer
Fig. 32
25
20
15
10
8,1 (7.000)
11,6 (10.000)
17,4 (15.000)
23,2 (20.000)
POTENZA TERMICA kW (kcal/h)
30
35
5
29,1 (25.000)
3.5.3
Pressure/heat output diagram for
L.P.G. gas (G31)
HEAT OUTPUT kW (kcal/h)
NOZZLE PRESSURE mbar
Fig. 34/a
