Publication No. 5105703
26 To Service the Boiler & Component Replacement
4.1
Preparing the Boiler for Servicing
Note: Boilers with side or rear flues have a flue elbow
fitted to the fluehood.
The elbow is replaced by an adapter on vertically flued
boilers.
A. Remove controls cover by opening the door covering
the securing screw on the underside of the controls
cover, see Fig. 14. Undo securing screw, pull controls
cover forward 10 mm, lower it to release it from its
four side fixings and pull forward clear of the
thermostat knob.
B. Remove door by undoing the lower fixing screws and
lift door off the two upper hinge brackets.
C. Remove screws securing the combustion chamber
front panel and remove panel.
D. Disconnect the fan supply leads from the connector
adjacent to the fan.
E. Remove the screws securing the fan mounting plate
leaving in place the three screws identified with a red
circle or adjacent ‘F’ mark in fan plate. Remove
mounting plate complete with fan.
F. Disconnect the two flexible tubes from the flue elbow
or adapter.
G. Loosen the two brass securing nuts beneath the flue
elbow outlet and remove the other two. Tilt the flange
and withdraw the elbow. Take care not to damage the
gasket. On vertically flued boilers remove the four
brass nuts and slide the vertical flue adapter up into
the flue duct.
H. Unscrew the four nuts and lift off the fluehood taking
care not to damage the rope seal.
Lower and lift out vertical flue adapter.
I. Undo the union on the gas service cock outlet.
J. Unplug the electrical supply leads for the gas control
valve from the control box. See Fig. 29.
K. Remove the screw securing the gas control valve to
its support bracket. See Fig. 29.
L. Disconnect electrode lead from electrode.
M. Remove two screws securing the burner assembly
to the bottom of the boiler case and lift out the burner
and gas control assembly.
4.2
Heat Exchanger
A. Working from above and below the heat exchanger
use a suitable brush and remove all deposits from
between the fins.
Slide vertical flue adapter into flue duct.
B. Refit the fluehood, ensuring that the rope seal is
undamaged and that a GOOD SEAL is made with the
heat exchanger. Fully tighten the four nuts.
C. Slide the flue elbow into the flue duct or lower flue
adapter and secure to the fluehood using four nuts.
Ensure that the gasket between the fluehood and
elbow or adapter is undamaged and a good seal is
obtained.
D. Reconnect flexible tubes to elbow or adapter.
Note: Red tube connects the front aluminium tube in
the upper chamber to the lower connection on elbow
or adapter, each being identified with a red ring.
4.3
Pilot Burner
The following operations are only necessary if the pilot
flame is distorted or the wrong size, i.e. too small.
A. Check that the pilot screw Fig. 26, is fully open (turn
anti-clockwise).
B. Unscrew the aluminium pilot tube from the pilot
assembly. Take care not to damage the electrode.
C. Unscrew the two hexagonal head screws securing
the pilot (and shield on 80) to the main burner and
remove the pilot assembly, be careful that the pilot
injector does not fall out during this operation.
D. Lightly brush the pilot and its shield to remove any
deposits. Remove the pilot injector and clean its
orifice or replace.
Note: Do not use a wire brush or pin to clean injector.
E. Gently clean any deposits from the electrode.
F. Refit the pilot injector to the pilot burner and assemble
the pilot to the aluminium tube.
G. Secure the pilot assembly to the main burner using
two hexagonal screws.
H. Fully tighten the union nut connecting the aluminium
tube to the pilot. Check for gas soundness at this
joint by following the procedure described in the
commissioning section of these instructions, Page
21.
I. Ensure that the spark gap is as illustrated in Fig. 30.
