Worcester 26CDi XTRA Installation And Servicing Instructions page 27

Fig. 35. Combustion Chamber Insulation
Combustion chamber front and
side assembly
Side
insulation
pad
Front insulation pad
When reassembling ensure these
locations are correctly fitted in the
slots at the rear of the inner casing
View from inside the combustion chamber
8. Burner Injector. See fig. 36.
Remove the burner as described in Section 13.3 (h).
Unscrew the brass injector from the burner and discard.
Fit the replacement injector and reassemble in the reverse order.
Fit the burner with the replacement injector in the reverse order
take care not to damage the electrode leads. When reassembling
the appliance follow the description in Section 13.3 (h).
Fig. 36. Burner and Electrode
Flame sensor
detail
Flame
sensor
position
Spark
electrode
assembly
3-4mm
Spark electrode
detail
9. Spark Electrode Assembly. See figs. 32 and 36.
Remove the combustion chamber front and sides as described in
13.3 (g)
Carefully pull off the two electrode leads.
Unscrew the M4 extended nut and remove the spark electrode
assembly from the burner and discard.
Fit the replacement electrode in the reverse order, check the
spark gap is 3 to 4mm.
Reassemble the appliance in the reverse order.
Side
insulation
10. Flame Sensor. See figs. 32 and 36.
pad
Remove the burner as described in Section 13.3 (h).
Undo the M3 screw and remove the sense electrode from the
burner.
Discard the electrode, retain the screw.
Fit the replacement electrode in the reverse order. checking that
the sense gap is 5 to 6mm.
Reassemble the appliance in the reverse order
11. Gas Valve. See figs. 27, 29, 32 and 37.
Check that the electricity and gas supplies to the appliance are
turned off.
Hinge down the facia panel into the Servicing Position as
described in Section 13.3 (c).
Remove the air pressure switch bracket as described in Section
14.3 (2). Ease the assembly clear of the gas valve.
Unscrew the two G
the two screws on the RHS securing gas valve bracket to the
appliance.
Remove the gas valve from the appliance.
Support the valve and carefully pull off the three electrical
solenoid plug connections. See fig. 29.
Discard the gas valve retain the screws.
Fit the replacement gas valve in the reverse order using new
sealing washers. Check the washers are correctly fitted.
Reassemble the appliance in the reverse order.
Turn on the gas supply and check for soundness.
To set the burner pressure. See fig. 29.
After a new gas valve has been fitted the burner pressures must
be set.
Follow the procedure described in Section 11.3 - Appliance
Operation.
Turn both the central heating control knob and the domestic
water control knob to their maximum position (i.e. fully
clockwise).
The maximum domestic hot water burner pressure must be set
first because it affects the other pressures.
Turn the gas mode switch, located behind the facia, to the
Burner injector
maximum position and open a hot water tap.
Adjust the maximum pressure adjustment screw on the gas
valve to give a burner pressure of 11.7 mbar for natural gas
(G20).
For propane (G31) the maximum pressure adjustment screw
should be fully screwed in to give a pressure of 35.5 mbar.
Close the hot water tap and turn the gas valve mode switch to
the minimum position.
Adjust the start pressure adjustment screw on the gas valve to
give a burner pressure of 0.9 mbar for natural gas (G20) or 2.9
mbar for propane (G31).
Turn the gas valve mode switch to the normal position.
Ensure the appliance lights in the central heating mode.
Turn the CH pressure adjuster fully clockwise, wait until the
Burner
burner pressure has stopped increasing and then slowly turn the
CH pressure adjuster anti clockwise until the burner pressure is
11.7 mbar for natural gas (G20) or 35.5 mbar for propane (G31).
Burner This will allow for maximum output to central heating.
fixing nut Important:
Check the data plate on the appliance to establish the required
output for the dwelling. Re-adjust the central heating output if necessary.
After completing the adjustments, check the pressure settings
and re-adjust as necessary.
Reassemble the appliance in the reverse order.
27
3 / inch union nuts on the gas valve. Remove
4