Worcester Highflow 3.5 OF Installation And Servicing Instructions page 21

Fig. 27
Domestic Hot Water
High Limit
Thermostat
Pump
Tundish Auto Air Vent Safety Valve
20. THE PUMP DELAY TIMER BOARD
(see Fig. 24.)
(a) Unscrew the two slotted M 5 screws located beneath the
control box and ease away the thermostat and pump delay
timer mounting bracket.
(b) Release the plastic catch on the end of each mounting post
pulling the printed circuit board forward approximately
3mm each time to prevent the plastic catch from returning.
It may be necessary to use an electrical screw driver to
assist in releasing the catches.
Pull the board off the mounting posts until it is free.
(c) Disconnect the electrical connections at the terminal strip.
(d) Locate the replacement board, with the leads at the top,
over the four mounting posts and push back squarely until
the plastic catch on the end of each post clicks into place.
(e) Reconnect the leads with the aid of the wiring diagram (Fig
11). It is important to reconnect the leads correctly.
20a. THE DHW HIGH LIMIT THERMOSTAT
See Fig 23.
(a) Remove the clip from the end of the overheat thermostat
phial pocket.
(b) Remove the thermostat phail from its pocket and feed it
out of the exposed hole at the left hand side of the electri-
cal box.
(c) Pull off the two electrical connectors at the thermostat.
Polarity is not important.
(d) Remove the thermostat centre post fixing nut situated
under the control panel.
Ease the thermostat out of its hole.
(e) Replace with a new thermostat in reverse order,
ensuring:-
(i) The split pin is replaced.
(ii) Any surplus capillary tube is coiled neatly, OUTSIDE
the control panel, in the space below the control panel.
21
The following components can be replaced if the cabinet
top panel is removed. See 17(a) preceding.
Check that the electrical supply has been disconnected.
21. THE CIRCULATING PUMP
(See Fig. 27.)
(a) Turn off the isolating valves mounted on the inlet and outlet
pump.
(b) Remove the left hand side panel support strap.
(c) Undo the two union nuts and remove the pump ensuring
that the sealing washers are not mislaid. If the connections
are found to be excessively tight then the left hand cabinet
side panel may be removed to give increased access.
(d) Remove the two screws holding the electrical cover on the
pump and disconnect the electrical leads noting the wire
positions.
(e) Fit the replacement circulating pump using new sealing
washers.
NOTE: The direction flow indicator on the circulating pump
should point towards the rear of the boiler. The replacement
pump, if fitted with a speed adjustment, should be set at
maximum speed.
(f) Open the isolating valves.
(g) Re-assemble the appliance in the reverse order.
22. THE FLOW REGULATOR
(See Fig. 29.)
(a) Turn off the mains cold water supply.
NOTE: A residue of the water will remain in the pipe
(b) Unscrew the flow regulator housing union nut and ease the
cold water connection aside.lt may be necessary to unclip
the supply pipe.
(c) Remove the sealing washer, wire filter and plastic flow
regulator. It may be necessary to prise the regulator from
its housing.
(d) Fit a new flow regulator, small diameter section first, and
re-assemble in the reverse order, replacin!~ the fibre sealing
washer. No sealing compound should be used.
23. THE SAFETY VALVE
(See. Fig 22.)
(a) Drain off the heating and domestic hot water systems.
(b) Unscrew the safety valve from the feed/vent pipe taking
care not to distort the pipe.
(c) Fit a new safety valve using an approved jointing
compound.
(d) Open all the radiators and fill the system, venting as
necessary. The appliance is fitted with an automatic air
vent on the heat bank.
The following components can be replaced if the cabinet
top panel, cabinet front panel, control box cover, inner
casing, control box and facia and combustion chamber
cover are removed. See 17(a), (b), (d), (e), (f) and (h)
preceding.
Check that the electrical supply has been disconnected.
24.
THE DIVERTER VALVE
(See Figs. 15 and 28.)
(a) Drain down the heating and domestic hot water systems.
(b) Disconnect the diverter valve leads at the terminal strip.
See Fig 11. Release the strain relief bush and carefully
withdraw the leads from the control box.
(c) Loosen the top connection on the diverter valve and
disconnect the other end of the elbow. Take care not to
mislay the washer.
(d) Release completely the left hand heat exchanger union
connection taking care not to mislay the washer.
(e) Release the remaining two union connections on the valve.
(f) Lift the valve upwards and to the left to separate it from
the pipes.
(g) Fit the replacement diverter valve with the manual override
lever facing downwards.
(h) Reconnect the leads ensuring that the strain relief bush is
replaced. Refer to the electrical wiring diagram (Fig. 11) to
ensure the correct connections have been made.