O Modulating Gas Valve; Function; Nomenclature; Adjustment - Biasi RIVA COMBI Service Manual

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Third Part
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Modulating Gas Valve

1) Function

2) Nomenclature

3) Adjustment

4) Checks

5) Removal of the Gas Valve

1 Function
The Modulating gas valve A in Figure 1 controls
the gas inflow to the boiler burner.
By means of an electric command given to the
on-off operators the passage of the gas through
the Modulating gas valve can be opened or
closed.
By means of an electric command given to the
modulation operator the pressure can be varied
and therefore the gas flow rate to the burner
(modulation). The modulation operator has
mechanical components which allow the
adjustment of the minimum and maximum
pressure exiting the valve.
2 Nomenclature
B Minimum gas pressure adjustment.
C Maximum gas pressure adjustment.
D Modulation operator's electric connectors.
E On-off operators electric connector.
F On-off operators.
G Gas valve inlet pressure test point.
RIVA COMBI SERVICE MANUAL – REV A
A
Figure 1
(edition-0106)
H Gas valve outlet pressure test point.
I Modulation operator.
Q
C
I
H
G
F
3 Adjustment
Warning: isolate the boiler from the mains
electricity supply before removing any
covering or component.
1) Remove the front panel of the case.
2) Open the gas valve inlet pressure test point
(G in Figure 2) 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 G.
4) Open the gas valve outlet pressure test point
(H in Figure 2) and connect the gauge.
5) Remove the protection cap L (Figure 3) from
the mechanical pressure adjustment
components levering with a flat screwdriver in
the slots M.
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.
Modulating Gas Valve
Figure 2
M
L
Figure 3
B
D
E
9-1