Publication No. 5105703
28 To Service the Boiler & Component Replacement
Removal/Replacement of Boiler Mounted Units
4.8
Gas Control Valve
This operation is most easily carried out by first removing
the burner and gas control valve assembly as follows:-
1. Switch off the external electricity supply by
disconnecting the plug at the socket or switching off
the external isolating switch.
2. Remove controls cover, case door and combustion
chamber front panel as described in 4.1.’Preparing
the Boiler for Servicing’, operations A, B and C.
3. Remove the burner and gas control assembly as
described in 4.1. ‘Preparing the Boiler for Servicing’,
operations I, J, K, L and M.
4. Disconnect the electrical supply wires from the gas
control valve noting their position. See Figs. 27 & 28.
5. Unscrew the union connecting the pilot supply pipe
to the gas control valve.
6. Separate the gas control valve from the flanges at
the inlet and outlet ports by removing the securing
screws.
Note: A spacer is used between the valve outlet and
the burner flange, requiring the use of two seals at
this point. See Fig. 26.
7. Use new seals on re-assembly.
8. Replacement is the reverse of removal.
9. Check that the burner pressure is in accordance with
the information on the data badge. If adjustment is
required, turn the pressure adjusting screw anti-
clockwise to increase pressure or clockwise to
decrease.
4.9
Fan
1. Switch off the external electricity supply by
disconnecting the plug at the socket or switching off
the external isolating switch.
2. Remove controls cover and case door as described
in 4.1.’Preparing the Boiler for Servicing’, operations
A and B.
3. Disconnect the fan supply leads from the connnector
adjacent to the fan.
4. Remove the screws securing the fan to the mounting
plate and remove fan.
5. Replacement is the reverse of removal.
6. Follow the full commissioning procedure as detailed
in the Commissioning section of these instructions
on page 21.
4.10
Main Burner
1. Switch off the external electricity supply by
disconnecting the plug at the socket or switching off
the external isolating switch.
2. Remove controls cover, case door and combustion
chamber front panel as described in 4.1.’Preparing
the Boiler for Servicing’, operations A, B and C.
3. Remove the burner and gas control assembly as
described in 4.1.’Preparing the Boiler for Servicing’,
operations I, J, K, L and M.
4. Unscrew the union nuts connecting the pilot supply
pipe to the pilot and gas control valve. Take care not
to damage the electrode and be careful that the pilot
injector does not fall out during this operation.
Remove sealing grommet and withdraw the pilot tube
through the hole in the burner mounting flange.
5. Separate the burner from the gas control valve at the
flanged connection by removing the four securing
screws.
Note: A spacer is used between the valve outlet and
the burner flange, requiring the use of two seals at
this point. See Fig. 26.
6. Unscrew the pilot, main burner injector and pressure
test nipple from the burner.
7. Use new sealing gaskets on re-assembly.
8. Replacement is the reverse of removal.
9. Follow the full commissioning procedure as detailed
in the Commissioning section of these instructions
on page 21.
4.11
Pilot/Ignition Electrode
1. Switch off the external electricity supply by
disconnecting the plug at the socket or switching off
the external isolating switch.
2. Remove controls cover, case door and combustion
chamber front panel as described in 4.1.’Preparing
the Boiler for Servicing’, operations A, B and C.
3. Disconnect the electrode lead from electrode.
4. Unscrew the aluminium pilot tube from the pilot
assembly. Take care not to damage the electrode.