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ROUTINE CLEANING AND INSPECTION
Note: Connecting pipework is telescopic, it may be
necessary to slide sleeve back for easier access to
filter.
• Clean and inspect filter, replace if necessary.
• With both flow restrictor and filter in place, re-
connect pipe to inlet connection and tighten.
• Fully open isolating cock on cold water inlet con-
nection and check for leaks.
REPLACEMENT OF PARTS
To replace microswitch assembly exept SB models)
• Disconnect microswitch by pulling off plug.
• Unclip external controls connector from mount-
ing bracket.
• Undo two screws securing microswitch assembly
to reversing valve assembly, see diagram 29.
• Remove microswitch assembly from reversing
valve.
• Fit replacement microswitch assembly in reverse
order to removal.
• Reconnect plug and refit external controls con-
nection to bracket.
To replace fan
• Disconnect power supply and earth leads to fan.
• Unscrew and remove two fan retaining screws
located at front edge of fan mounting plate.
• Remove fan with mounting plate attached by
pulling forwards and out of boiler.
• Unscrew and remove three screws securing fan
to fan mounting plate.
• Fit replacement fan to mounting plate and se-
cure with screws.
• Fit replacement fan to boiler in reverse order to
removal making sure that mounting plate retain-
ing lugs are properly engaged into flue hood.
• Reconnect power supply and earth leads.
Important: Make sure that fan outlet is correctly fit-
ted into either the flue elbow for top outlet flue, or
the rear connector for rear outlet flue.
Before commissioning boiler, remove the two plas-
tic transit clips from replacement fan.
To replace air pressure switch
• Locate air pressure switch in upper left hand cor-
ner of sealed chamber.
• Pull off plastic tube from left hand connection.
• Grasp pressure switch and disengage it from
bracket clips by pulling from the top.
• Remove electrical connections from switch.
• Fit electrical connections to terminals 1 and 3 of
replacement switch.
• Fit replacement switch in reverse order to re-
moval.
Important: Refit plastic tube to LEFT hand connec-
tor (marked P1).
To replace spark generator
• Locate spark generator on bracket to right hand
side of gas valve.
• Undo and remove screw securing lower termi-
nal cover to bracket and remove bracket.
• Disconnect four leads from spark generator.
Operation of water valve (exept SB models)
• With the Summer/Winter control in the 'Summer'
position, slowly open a convenient tap until boiler
lights.
• Measure water flow, it should not be greater than
3,5 litres/minute.
• If necessary, replace diaphragm.
• Replace all outer panels.
microswitch on THEMA F 23 E
Diagram 29
Diagram 30
• Undo and remove screw securing spark genera-
tor to bracket and remove spark generator.
• Fit replacement spark generator in reverse order
to removal.
• Reconnect two grey power supply leads and two
clear ignition leads to spark generator, the polarity
is not important.
• Refit lower terminal cover.
To replace main printed circuit board (PCB)
• With lower front panel down as described previ-
ously, undo and remove screw holding pump con-
nection cover to PCB cover, see diagram 30.
• Open cover and unclip plastic clip securing
pump cable to lower front panel.
• Pull off pump connector and earth lead.
• Undo and remove four screws securing PCB
cover to lower front panel.
• Lift off PCB cover.
• Pull off connectors CN6, CN7, CN8 and CN9 on
PCB.
• Undo and remove screw holding PCB to lower
front panel.
• Lifting PCB up slightly on LHS, pull PCB out of elec-
trical connector on ignition PCB. Leave ignition PCB
in place.
19
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