17
221462C
7 Servicing and Replacement of Parts
7.6 Electrode
Generally follow the instructions given in Section 7.1.
Unscrew the electrode from the pilot shield.
When refitting check that the spark gap is as diagram 7.7.
7.7 Over Heat Cutoff Device
Generally follow the instructions given in Section 7.1.
Remove the screws securing the over heat cutoff device to the
clamp, see diagram 7.8.
Release the cutoff connectors at the gas valve, see diagram 7.9.
Remove the screw retaining the grommet plate to the rear panel
to release plate, see diagram 7.10.
Carefully remove, one at a time, the cables of the cutoff through
the grommet.
When reassembling use a little of the heat sink compound,
supplied, on the face of the cutoff to make sure of a good contact
with the pipe also make sure it is correctly located.
7.8 Gas Valve
Generally follow the instructions given in Section 7.1.
Remove screw to release gas valve cover.
Disconnect all leads and pipes at valve.
Undo the four screws each side of the valve to release the
service cock and burner supply tube, take care not to damage
the “O” rings.
Remake all connections.
Do not tighten the thermocouple nut more than a quarter turn
beyond finger tight.
It will be necessary to purge pipework and gas valve before
relighting, refer to Commissioning.
7.9 Electrical Control Box
Remove controls cover and outer casing as above.
Remove retaining clip from boiler thermostat phial pocket and
withdraw the phial, see diagram 7.8.
Remove the control box by undoing the two fixing screws at the
front and lower the front of the box until it is clear of the cover.
Push the box towards the rear of the boiler to disengage the hinge
and lower, see diagram 5.1.
Withdraw the control thermostat capillary through the bottom of
the air duct.
Disconnect cables (a) mains, L. N and E (b) pump at terminal 8,
7 and earth stud, (c) cables at gas valve, (d) disconnect any
remote controls at terminals 9 and SL.
When replacing refer to diagram 5.2 for electrical connections.
Smear the control thermostat phial with heat sink compound
and make sure it is secured with the retainer, in the pocket.
7.10 Piezo Unit
Gain access generally as Section 7.1.
Disconnect ignition lead and remove backing nut from piezo
unit.
7.11 Ignition Lead
Gain access generally as Section 7.1.
Disconnect the ignition lead at both ends.
When replacing the clear end fits to the electrode.
7.12 Control Thermostat
Gain access generally as Section 7.1.
Remove and support the control box.
Remove the control knob and electrical connections from the
control thermostat body.
Pull off the connectors from the control thermostat terminals.
Remove the two screws securing the control thermostat to the
control box. The control thermostat can now be removed.
When replacing smear the control thermostat phial with a little
heat sink compound, supplied, before fitting into the pocket.
Diagram 7.10
OVERHEAT CUT-OFF
REMOVAl
GROMMET
GROMMET
PLATE
(behind duct)
SECURING
SCREW for
Grommet Plate
0787
Diagram 7. 11
GAS VALVE
COVER
SOLENOID
SECURING
SCREW
RETAINING
CLIP
ELECTRICAL
CONNECTORS
3782
