Function; Modulating Gas Valve; Nomenclature Of The Parts; Adjustment - Biasi GARDA M90F.24S Service Manual

10

Modulating gas valve

10.1

Function

The Modulating gas valve A in Fig. 41 controls the gas
inflow to the boiler burner.
A
Fig. 41
By means of an electric command given to the on---off
operators the passage of the gas through the Modula-
ting gas valve can be opened or closed.
By means of an electric command given to the modula-
tion operator the pressure can be varied and therefore
the gas flow rate to the burner (modulation). The mo-
dulation operator has mechanical components which
allow the adjustment of the minimum and maximum
pressure exiting the valve.
10.2 Nomenclature of the parts (Fig. 42)
1 Modulation operator's electric connectors
2 Minimum gas pressure adjustment
3 On---off operators
4 Maximum gas pressure adjustment
5 On---off operators electric connector
6 Gas valve inlet pressure test point
7 Modulation operator
8 Gas valve outlet pressure test point
22
8
7
6 5
Fig. 42
10.3

Adjustment

Warning: isolate the boiler from the mains
electricity supply
covering or component.
1 Remove the front panel of the case.
2 Open the gas valve inlet pressure test point (6 in
Fig. 42) at the valve input, connect a suitable
pressure gauge and check the gas pressure of
the supply network.
3 Remove the gauge and close the pressure test
point 6.
4 Open the gas valve outlet pressure test point (8
in Fig. 42) and connect the gauge;
5 Remove the protection cap from the mechanical
pressure adjustment components;
6 Start the boiler at its maximum power.
Operate the boiler in d.h.w. mode or ensure that
the boiler is not range rated if the test is carried out
in c.h. mode.
7 Rotate the maximum gas pressure adjustment (4
in Fig. 42) until you obtain the required pressure
(by rotating clockwise the pressure increases).
8 Disconnect one of the two connectors (1 in
Fig. 42) or, alternatively, remove the service panel
as explained in the section 2.3 of this manual and
set the dip---switch selector 1 (see section 9.5) to
the OFF position.
9 Rotate the minimum gas pressure adjustment (2
in Fig. 42) until you obtain the required pressure
(by rotating clockwise the pressure increases).
10 Turn the boiler off and re---connect the wire to the
modulating operator (or set the dip---switch se-
lector 1 back to the ON position).
11 Start the boiler and check again the maximum
gas pressure setting.
12 Turn the boiler off and disconnect the gauge.
Important: after the gas pressure checks and any
adjustment operations, all of the test points must be
sealed.
1
2
3
4
before removing any