Saunier Duval THEMA F 23 E Installation And Servicing Instructions Download Page 20

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• Fit replacement PCB in reverse order to removal.

Important:

When fitting replacement PCB, ensure

that control knob spindles correctly locate into PCB
adjuster slots.
• Refit connectors and covers in reverse order to
removal.

To replace ignition PCB

• Gain access to PCB's as described in previous
section.
• Remove main PCB securing screw as described
in previous section.
• Pull off three electrical connectors on PCB.
• Lift up ignition PCB, separate from main PCB and
remove from boiler.
• Fit replacement PCB in reverse order to removal.
• Refit connectors and covers in reverse order to
removal.

To replace pump

• Drain down heating circuit of boiler only as fol-
lows:
• Close isolating valves on flow and return connec-
tions on fixing jig,

see diagram 5.

Note:

These valves are closed when slots are at right

angles to direction of flow.
It is not necessary to drain entire heating circuit to
carry out this work.
• Drain boiler by attaching a plastic tube to drain
outlet and opening drain valve knob anticlockwise,

see diagram 5.

• Gain access to pump connection as described
in '

To replace main PCB'.

• Pull off pump connector and earth lead.
• Pull out retaining clip from telescopic pump out-
let connection and slide connection upwards to
release from pump.
• Undo and remove two fixing screws and remove
pump retaining bracket from front of pump.
• Grasp pump body, lift upward to disengage from
reversing valve and turn pump to right. Remove
pump by pulling forward and over reversing valve
assembly.
• Discard old pump inlet 'O' ring.
• Apply silicone grease to new 'O' ring supplied,
and fit onto inlet connection on replacement
pump.
• Fit replacement pump in reverse order to re-
moval.

Note:

Apply silicone grease to pump outlet con-

nection 'O' ring before assembly.
• Refit pump electrical connection.
• Open isolating valves on flow and return connec-
tions, refill, vent and pressurise boiler. Check for leaks.

To replace temperature/pressure gauge

• Drain down heating circuit of boiler only as de-
scribed in '

To replace pump'.

• Undo and remove screw securing pressure
gauge capillary to front section,

see diagram 31.

• Carefully pull capillary from front section.
• Undo and remove two screws securing tempera-
ture/pressure gauge to lower front panel and re-
move gauge.
• Fit replacement gauge in reverse order to
removal.

REPLACEMENT OF PARTS

• Fit capillary of new gauge to front section using
new 'O' ring supplied.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.

To replace reversing valve assembly

• Remove temperature/pressure gauge capillary
as described previously.
• Remove pump as described previously.
• Remove microswitch assembly as described pre-
viously.
• Remove retaining clip from LHS pipe connection
on front section of valve and disengage pipe.
• Unscrew and disconnect heating flow (centre)
connection at fixing jig.
• Remove retaining clip from heating flow pipe
connection on right of front section.
• Remove flow pipe from boiler.
• Unscrew and disconnect heating return (left
hand) connection at fixing jig.
• Remove retaining clip from expansion vessel pipe
connection at rear of reversing valve assembly and
disengage pipe, pushing pipe back and out of re-
versing valve.
• Undo and remove large screw holding water
valve to back plate of reversing valve assembly,