Gas Valve (Fig. 30); Electrodes (Fig. 31); Expansion Vessel (Fig. 32); Heat Exchanger (Fig. 33) - Riello Vokera VISION PLUS 20 S User Instructions

7.18 GAS VALVE
(FIG. 30)
Carry out component removal procedure as described in 7.9.
The gas valve must be changed as complete unit. Disconnect
the electrical plug and leads from the gas valve, slacken and
unscrew gas valve inlet and outlet connections. Please note,
the sealing washers (Q) must be discarded and replaced with
new sealing washers. Disconnect the compensation pipe (R).
Unscrew gas pipe connections (S-T), the gas valve can now
be removed. Replace in the reverse order. Check and adjust
burner pressure settings.
WARNING, A GAS TIGHTNESS CHECK MUST BE CAR-
RIED OUT.
7.18.1 INJECTOR (FIG. 30)
Carry out component removal procedure as described in 7.9.
Unscrew and remove gas pipe connections (S-T). Locate and
remove the injector (U) inside the valve. Replace in the reverse
order. Check and adjust burner pressure settings.
WARNING, A GAS TIGHTNESS CHECK MUST BE CAR-
RIED OUT.
7.19 ELECTRODES
Carry out component removal procedure as described in 7.9.
Remove the air chamber front cover. Disconnect the electrode
leads and ancillary wiring from their respective connectors. Re-
move the retaining screws (V) for electrode. Remove the spark
ignition electrode (W). Remove the flame sensor electrod (Y).

7.20 EXPANSION VESSEL (FIG. 32)

Carry out component removal procedure as described in 7.9.
Disconnect the flexible expansion pipe from the vessel. Un-
screw the nut that secures the vessel to the lower frame. Locate
and remove the screw (Z) that secures the vessel to the top.
Disconnect the connection pipe (Z1).
The expansion vessel can now be removed. Replace in the
reverse order. Ensure all seals are in good condition, taking
care to ensure they are replaced correctly.

7.21 HEAT EXCHANGER (FIG. 33)

Refer to 7.9 and carry out the component removal procedure.
- Loosen the nuts on the 2 ramps (A and B).
- Remove the clips (C) to remove the 2 ramps (A and B).
- Remove the 2 ramps (A and B) from the exchanger.
- Remove the condensate drain pipe (D).
- Withdraw the rain protection drain pipe (H).
- Disconnect the flue gas probe connector.
- Remove the screw (F) of the flue gas analysis socket and
remove the cap.
- Remove the screw (G) that fixes the rain cover.
- Unscrew the 4 screws (E) that secure the exchanger to the seat
- Remove the exchanger.
Once all the operations have been completed, reassemble
all the components operating in the opposite direction to that
described.
Pay particular attention to the insertion of ramps A and B, use
tongs at the base of the signposting to avoid the overshoot at
the inlet of the exchanger connections
Restore voltage and gas supply to the boiler.
7.21.1 REMOVING THE RETARDER INSULATION PANEL
Removing the retarder insulation panel
- Carry out the component removal procedure as described
in the chapter "7.22 combustion unit"
- Protect the lower part of the internal coils of the exchanger
to prevent dust and parts of the insulating panel from falling
into them during subsequent operations.
THE CHARACTERISTICS OF THE MATERIAL MAKE THE
INDIVIDUAL PROTECTION DEVICES NOT NECESSARY
BUT, FOR SAFETY, WE RECOMMEND THE USE OF A MASK,
GLOVES AND PROTECTIVE GLASSES.
- With the aid of a blade, cut the insulating panel to be replaced
approximately 60 mm from the circumference.
- Lift and remove the 2 pieces of panel from the seat.
- The panel is fixed with a clip; if, during the removal opera-
tions, the clip should remain fixed to the relative pin, remove
it by unscrewing it or, if damaged, with the aid of a pliers.
- Vacuum any residual material present on the exchanger
coils and retarder support.
- Position the new retarder insulation panel near the seat and
insert it fully by pressing on the central part.
- Once all the operations have been completed, reassemble
all the components operating in the opposite direction to that
described.
- Restore voltage and gas supply to the boiler
34
(FIG. 31)
T
Fig. 30
Fig. 31
Fig. 32
H
E
E
tongs
tongs
position
position
D
B
Fig. 33
S
Q
U
Q
W
V
Y
Z
Z1
G
F
E
C
C