Worcester Highflow 400 BF, Installation And Servicing Instructions

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CAUTION: Some water will remain in the expansion vessel,
pump, water diverter valve, water to water heat exchanger and
gas to water heat exchanger. Extra care must be taken when
removing these components.
Place a towel or cloth beneath the component to absorb the
excess system water.
The water will be contaminated and any absorbent material
used must be destroyed or washed thoroughly after any
component has been replaced.
Any inhibitor in the primary water must be replenished.
(a) Appliance Heatbank and Heating Circuit
Turn off the central heating flow and return valves at the
appliance using a flat blade screwdriver. See Fig. 16. Remove the
kick strip secured to the cabinet side panels and base plate with
five screws. See Fig. 12. Fit a tube to the drain tap located on the
right hand side, front, of the heatbank and open the tap. See
Figs. 1 and 12.
Note: The heatbank contains about 60 litres of primary water
sufficient time must be allowed to drain the heatbank. Close the
drain tap when the flow has stopped.
(b) Appliance Hot Water Circuit
Turn off the mains water supply valve at the appliance using
a flat blade screwdriver. See Fig. 16. Fit a tube to the drain
tap located on the left hand side of the gas valve. See Fig. 16.
Open the tap and drain the hot water circuit.
A quantity of water will remain in the water to water heat
exchanger, extra care must be taken when removing this
component.
15.3 COMPONENT REPLACEMENT
1. Automatic Air Vent.
See Fig. 23.
Check that the electricity supply to the appliance is turned off.
Remove the cabinet front panel, place the facia and control box
in the Service Position, lower the expansion vessel into the
Service Position and remove the inner casing cover, as described
in Section 14.2 a, b, c and d.
Drain the heating circuit as described in Section 15.2(a).
Unscrew the automatic air vent and discard. Fit the replacement
assembly. Ensure the plastic cap is removed and discarded.
Open the valves, fill and re-pressurise the system as described in
Section 12.2.
Ensure the joint is water tight. Reassemble the appliance in the
reverse order.
2. Gas to Water Heat Exchanger. See Figs. 23 and 24.
Check that the electricity supply to the appliance is turned off.
Remove the cabinet front panel, place the facia and control box
in the Service Position, lower the expansion vessel into the
Service Position and remove the inner casing cover, as described
in Section 14.2 a, b, c and d.
Drain the heating circuit as described in Section 15.2 (a).
Remove the flue hood and combustion chamber cover as
described in Sections 14.2 e and f. Unscrew the retaining screws
and remove the Safety Temperature Limiter and CH primary
sensor from the thermostat pad as described in Section 15.3 - 12.
Remove the left hand fibre insulation pad from the combustion
chamber. Remove the access cover in the left hand side of the
combustion chamber held in position with one screw.
Unscrew the front and rear heat exchanger union connections.
Lift the heat exchanger off the right hand side of the combustion
chamber support and clear of the union connections. Remove
the heat exchanger clear of the inner casing.
CAUTION: There will be a small quantity of water remaining in
the heat exchanger. Follow the procedure as described in
Section 15.2.
Discard the heat exchanger.
Fit the replacement heat exchanger in the reverse order using
new fibre sealing washers. Ensure the washers are in place and
the heat exchanger correctly aligned.
Tighten the union connections. Refit the access cover to the left
hand side of the combustion chamber and replace the fibre
insulation pad. Refit the combustion chamber cover. Refit the
sensor and thermostat with a layer of heat sink compound.
Refer to the wiring diagram Fig. 7.
Reassemble the appliance in the reverse order.
Open the valves, fill and re-pressurise the system as described in
Section 12.2.
3. Combustion Chamber Insulation. See Figs. 23 and 25.
Check that the electricity supply to the appliance is turned off.
Remove the cabinet front panel, place the facia and control box
in the Service Position, lower the expansion vessel into the
Service Position and remove the inner casing cover, as described
in Section 14.2 a, b, c and d.
Drain the heating circuit as described in Section 15.2 (a).
Remove the combustion chamber cover as described in
Section 14.2 (f).
Remove the gas to water heat exchanger as described in
Section 15.3.2.
Remove the fibre insulation pads from the combustion chamber
side, rear and front sections and discard.
Fit replacement fibre insulation pads in the reverse order.
Note: The fibre is fragile take care it is not damaged.
Ensure the insulation pad fitted to the combustion chamber
cover has the pilot observation hole correctly aligned.
Reassemble the appliance in the reverse order.
Open the valves, fill and re-pressurise the system as described in
Section 12.2.
4. Main Burner. See Figs. 20 and 23.
Check that the electricity supply to the appliance is turned off.
Remove the cabinet front panel, place the facia and control box in the
Service Position, lower the expansion vessel and remove the inner
casing cover, as described in Section 14.2 a, b, c and d.
Remove the combustion chamber cover and main burner assembly
as described in Sections 14.2 f and g. Discard the burner.
Fit a replacement main burner in the reverse order. Ensure the main
burner is fitted correctly on the main burner injector located at the
back of the inner casing. Reassemble the appliance in the reverse order.
Front union connection
Fibre sealing washer
Fibre sealing washer
Rear union connection
Gas to water heat
exchanger
Remove access cover
Warning: There will be a small quantity of
water remaining in the heat exchanger.
Fixing screw
Remove left-hand fibre insulation pad
Fig. 24. Gas to water heat exchanger.