Section 17. Replacement Of Parts - Worcester Highflow 3.5 OF Installation And Servicing Instructions

Fig. 15.
Combustion Chamber Fixing Screws
Heat Exchanger
Union Connections
Boiler Limit Thermostat
(d) Inspect the pilot burner and ignition electrode. Ensure that
they are clean and in good condition. Check that the spark
is 3-4mm (0.14 in.). See Fig. 17.
(e) Check that the thermocouple tip is not burned or cracked.
If it shows any sign of damage a new thermocouple must
be fitted.
(f) Re-assemble the burner components in the reverse order,
not forgetting the pilot and main burner injectors. Do not
fully tighten the pilot pipe at this stage.
4.
CLEANING THE HEAT EXCHANGER
(See Fig. 13.)
(a) Cover the pilot gas inlet adaptor and the main gas inlet
within the combustion chamber.
(b) Using a suitable brush, clean the inside surface of the heat
exchanger and the fins.
(c) Clean the flue duct.
(d) Remove any deposits which fall to the bottom of the boiler
casing.
(e) Check the condition of the rear, sides and front combustion
chamber insulation pieces. Renew if necessary. See
Section 17, Replacement of Parts-Section 6.
5. RE-ASSEMBLY
Re-assemble the boiler in the reverse order to the dis-
mantling procedure.
(a) Replace the flue hood on to the heat exchanger ensuring
that the hood is properly located on the heat exchanger.
(b) Locate the' J' bolts in the side brackets, ensuring that they
are hooked into the bracket, and hand tighten. Do not over
tighten.
(c) Replace the burner and pilot assembly locating the
positioning bracket into the bracket in the combustion
chamber.
(d) Secure the burner manifold with the extended M5 screws
checking that the 0-ring is in position.
(e) Connect and tighten the pilot feed pipe at the adaptor. Fully
tighten the connection at the pilot assembly.
(f) Reconnect the thermocouple.
'(g) Reconnect the Piezo-electric igniter lead to the electrode.
(h) Check that all joints are tight.
(i) Replace the combustion chamber front plate.
15
(j) Brush any dust or deposits from the
~1as
control and
associated pipework.
(k) Re-assemble the cabinet in the reverse order to its removal.
Do not fit the inner casing or the cabinet front panel at this
stage.
6. TEST APPLIANCE AND INSTALLATION
(a) Turn on the gas at the gas service cock and re-connect the
electrical supply.
(b) Refer to the lighting instructions on the jacket front panel.
(c) Carefully light the boiler and check for gas soundness
including the burner manifold connection within the
combustion chamber in accordance with BS 6891. It is
necessary to operate the boiler for a short period with the
boiler inner casing removed. The action must be under-
taken with great care. Turn off the boiler and replace the
boiler inner casing immediately after checking the gas
soundness. Check the main burner through the viewing
window.
(d) With the central heating OFF, check that the domestic hot
water operates correctly. When the priority thermostat is
satisfied, switch the central heating on and check that the
diverter valve operates and supplies hot water to the central
heating circuit.
(e) Set the 3-position switch (or programmer) to OFF.
(f) Loosen the burner pressure test point one turn and connect
a pressure gauge. See Fig. 20. Set the 3-position switch
(or programmer) to HOT WATER and CENTRAL HEATING
(24 hrs) setting. Set the hot water thermostat to OFF and
the central heating thermostat to MAXIMUM. If necessary
adjust the gas pressure at the governor on the gas valve.
See Section 13.
(g) Set the 3-position switch (or programmer) to HOT WATER.
Turn the central heating thermostat to OFF and the hot
water thermostat to MAXIMUM. If necessary adjust the
gas pressure at the governor on the gas valve. See Section
13.
(h) Set the controls to OFF. Disconnect the pressure gauge and
retighten the test point screw. Re-light and test for gas
soundness around the test point screw.
(i) Before leaving the site the service engineer should check
that no flammable material is left inside the appliance
casing and that the ventilation requirements remain at the
required standard. See Section 6.
(j) If the appliance is fitted in a cupboard check that the
cupboard ventilation remains adequate. See Section 6.
(k) Refit the facia, cabinet front panel and top panel.
17. REPLACEMENT OF PARTS
WARNING: Disconnect the electrical supply at the mains and
turn off the gas service cock before commencing any work.
To replace appliance parts it is necessary to remove one or more
sections of the cabinet and cover plates within the boiler as
described below.
(a) Cabinet Top Panel: Snatch squarely upwards to release the
clips.
(b) Cabinet Front Panel: Pull firmly at the base to release the
clips and lift upwards and out.
(c) Facia Panel: Remove the six pozi-drive screws and the plug-
in terminal strip connection. See Fig. 2. Remove the
remaining screw in the right hand side panel to allow the
removal of the facia.
(d) Control Box and Facia: Remove the cabinet top and front
panels. Release the three pozi-drive screws, and rest the
assembly on the appliance. See Fig. 2. Release the
remaining screw in the right hand side panel to allow the
removal of the control box and facia.
(e) Inner Casing: Remove the six slotted hexa!JOn head screws
and washers. (See Fig. 23.)
(f) Combustion Chamber Panel: Remove the six slotted
hexagon head screws.